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Postoperative pain occurs in as many as 70% of the over 230 million surgeries performed annually worldwide. Postoperative pain management still relies on opioids despite their negative consequences, resulting in a public health crisis. Therefore, it is of utmost importance to develop alternative therapies to treat chronic pain. Natural products derived from medicinal plants are potential sources of novel and biologically active compounds for development of safe analgesics. Hence, in this study, we screened a library of natural products to identify small molecules that target the activity of voltage-gated sodium and calcium channels which have important roles in nociceptive sensory processing.Fractions derived from the Native American medicinal plant, Parthenium incanum, were assessed using depolarization-evoked calcium influx in rat dorsal root ganglion (DRG) neurons. Further separation of these fractions yielded a cycloartane-type triterpene identified as argentatin C, which was additionally evaluated using whole-cell voltage and current clamp electrophysiology, and behavioral analysis in a mouse model of postsurgical pain.We found that argentatin C blocked the activity of both voltage-gated sodium and LVA calcium channels in calcium imaging assays. Docking analysis predicted that argentatin C may bind to NaV1.7-1.9 and CaV3.1-3.3 channels. Furthermore, argentatin C decreased NaThese results suggest that the dual effect of argentatin C on voltage-gated sodium and calcium channels supports its potential as a novel treatment for painful conditions.

Physachenolide C (1) is a 17β-hydroxywithanolide natural product with a unique anticancer potential, as it exhibits potent and selective in vitro antiproliferative activity against prostate cancer (PC) cells and promotes TRAIL-induced apoptosis of renal carcinoma (RC) and poly I:C-induced apoptosis of melanoma cells. To explore the effect of ring A/B modifications of physachenolide C (1) on these biological activities, 23 of its natural and semisynthetic analogues were evaluated. Analogues 4-23 were prepared by chemical transformations of a readily accessible compound, physachenolide D (2). Compound 1 and its analogues 2-23 were evaluated for their antiproliferative activity against PC (LNCaP and 22Rv1), RC (ACHN), and melanoma (M14 and SK-MEL-28) cell lines and normal human foreskin fibroblast (HFF) cells. Most of the active analogues had selective and potent activity in reducing cell number for PC cell lines, some showing selectivity for androgen-independent and enzalutamide-resistant 22Rv1 cells compared to androgen-dependent LNCaP cells. Analogues with IC50s below 5.0 μM against ACHN cells, when tested in the presence of TRAIL, showed a significantly increased ability to reduce cell number, and those analogues active against the M14 and SK-MEL-28 cell lines exhibited enhanced activity when combined with poly I:C. These data provide additional structure-activity relationship information for 17β-hydroxywithanolides and suggest that selective activities of some analogues may be exploited to develop natural products-based tumor-specific agents for cancer chemotherapy.

Six new 6-isopentylsphaeropsidones, strobiloscyphones A-F (1-6), and a new hexadecanoic acid, (2Z,4E,6E)-8,9-dihydroxy-10-oxohexadeca-2,4,6-trienoic acid (7), together with sphaeropsidone (8) and its known synthetic analogue 5-dehydrosphaeropsidone (9) were isolated from Strobiloscypha sp. AZ0266, a fungus inhabiting the leaf litter of Douglas fir (Pseudotsuga menziesii). The structures of 1-7 were established on the basis of their high-resolution mass and 1D and 2D NMR spectroscopic data, and their relative and/or absolute configurations were determined by NOE, comparison of experimental and calculated ECD spectra, and application of the modified Mosher's ester method. Of these, strobiloscyphone F (6) contains a novel highly oxygenated tetracyclic oxireno-octahydrodibenzofuran ring system. Natural products 1, 6, and 9 and the semisynthetic analogue 12 derived from 8 exhibited cytotoxic activity, whereas 9 and 12 showed antimicrobial activity. Possible biosynthetic pathways to 1-6, 8, and 9 are proposed.

Multiple myeloma (MM) is a hematological cancer in which relapse and resistance are highly frequent. Therefore, alternatives to conventional treatments are necessary. Withaferin A, a withanolide isolated from Withania somnifera, has previously shown promising activity against various MM models. In the present study, structure-activity relationships (SARs) were evaluated using 56 withanolides. The antiproliferative activity was assessed in three MM cell lines and in a 3D MM coculture model to understand the in vitro activity of compounds in models of various complexity. While the results obtained in 2D allowed a quick and simple evaluation of cytotoxicity used for a first selection, the use of the 3D MM coculture model allowed filtering compounds that perform better in a more complex setup. This study shows the importance of the last model as a bridge between 2D and in vivo studies to select the most active compounds and ultimately lead to a reduction of animal use for more sustained in vivo studies. NF-κB inhibition was determined to evaluate if this could be one of the targeted pathways. The most active compounds, withanolide D (2) and 38, should be further evaluated in vivo.

Aeroponically grown Physalis acutifolia afforded five new and six known withanolides including 10 physalins. The structures of the new withanolides, acutifolactone (1), 5β,6β-epoxyphysalin C (2), 5α-chloro-6β-hydroxyphysalin C (3), and an inseparable mixture of 5β,6β-epoxy-2,3-dihydrophysalin F-3β-O-sulfate (4) and 5β,6β-epoxy-2,3-dihydrophysalin C-3β-O-sulfate (5), were elucidated by analysis of their spectroscopic data and chemical interconversions. The known withanolides were identified as physalins B (6), D (7), F (8), H (9), I (10), and U (11) by comparison of their spectroscopic data with those reported. Evaluation of 1-11 and the derivatives, 13 and 13a, obtained from 4 and 5 against a panel of four human cancer cell lines [NCI-H460 (non-small-cell lung), SF-268 (CNS glioma), PC-3 (prostate adenocarcinoma), and MCF-7 (breast adenocarcinoma)] and normal human lung fibroblast (WI-38) cells revealed that physalins 2, 3, 8, and 9 exhibited selective cytotoxic activity to at least one of the cancer cell lines tested compared to the normal cells and that 7, 10, and 11 were inactive up to a concentration of 10.0 μM. These data provided some preliminary structure-activity relationships and suggested that the mechanism of cytotoxic activity of physalins may differ from other classes of withanolides.

For an affliction that debilitates an estimated 50 million adults in the United States, the current chronic pain management approaches are inadequate. The Centers for Disease Control and Prevention have called for a minimization in opioid prescription and use for chronic pain conditions, and thus, it is imperative to discover alternative non-opioid based strategies. For the realization of this call, a library of natural products was screened in search of pharmacological inhibitors of both voltage-gated calcium channels and voltage-gated sodium channels, which are excellent targets due to their well-established roles in nociceptive pathways. We discovered (-)-hardwickiic acid ((-)-HDA) and hautriwaic acid (HTA) isolated from plants, Croton californicus and Eremocarpus setigerus, respectively, inhibited tetrodotoxin-sensitive sodium, but not calcium or potassium, channels in small diameter, presumptively nociceptive, dorsal root ganglion (DRG) neurons. Failure to inhibit spontaneous postsynaptic excitatory currents indicated a preferential targeting of voltage-gated sodium channels over voltage-gated calcium channels by these extracts. Neither compound was a ligand at opioid receptors. Finally, we identified the potential of both (-)-HDA and HTA to reverse chronic pain behavior in preclinical rat models of HIV-sensory neuropathy, and for (-)-HDA specifically, in chemotherapy-induced peripheral neuropathy. Our results illustrate the therapeutic potential for (-)-HDA and HTA for chronic pain management and could represent a scaffold, that, if optimized by structure-activity relationship studies, may yield novel specific sodium channel antagonists for pain relief.

Chronic pain can be the result of an underlying disease or condition, medical treatment, inflammation, or injury. The number of persons experiencing this type of pain is substantial, affecting upwards of 50 million adults in the United States. Pharmacotherapy of most of the severe chronic pain patients includes drugs such as gabapentinoids, re-uptake blockers and opioids. Unfortunately, gabapentinoids are not effective in up to two-thirds of this population and although opioids can be initially effective, their long-term use is associated with multiple side effects. Therefore, there is a great need to develop novel non-opioid alternative therapies to relieve chronic pain. For this purpose, we screened a small library of natural products and their derivatives in the search for pharmacological inhibitors of voltage-gated calcium and sodium channels, which are outstanding molecular targets due to their important roles in nociceptive pathways. We discovered that the acetylated derivative of the ent-kaurane diterpenoid, geopyxin A, 1-O-acetylgeopyxin A, blocks voltage-gated calcium and tetrodotoxin-sensitive voltage-gated sodium channels but not tetrodotoxin-resistant sodium channels in dorsal root ganglion (DRG) neurons. Consistent with inhibition of voltage-gated sodium and calcium channels, 1-O-acetylgeopyxin A reduced reduce action potential firing frequency and increased firing threshold (rheobase) in DRG neurons. Finally, we identified the potential of 1-O-acetylgeopyxin A to reverse mechanical allodynia in a preclinical rat model of HIV-induced sensory neuropathy. Dual targeting of both sodium and calcium channels may permit block of nociceptor excitability and of release of pro-nociceptive transmitters. Future studies will harness the core structure of geopyxins for the generation of antinociceptive drugs.

Withanolides constitute a valuable class of bioactive natural products because some members of the class are known to exhibit cytotoxic activity and also induce a cytoprotective heat-shock response. In order to understand the relationship between their structures and these dual bioactivities of the withanolide scaffold, we obtained 25 analogues of withaferin A (WA) and withanolide D (WD) including 17 new compounds by semisynthesis involving chemical and microbial transformations. Hitherto unknown 16β-hydroxy analogues of WA and WD were prepared by their reaction with triphenylphosphine/iodine, providing unexpected 5β-hydroxy-6α-iodo analogues (iodohydrins) followed by microbial biotransformation with Cunninghamella echinulata and base-catalyzed cyclization of the resulting 16β-hydroxy iodohydrins. Evaluation of these 25 withanolide analogues for their cytotoxicity and heat-shock-inducing activity (HSA) confirmed the known structure-activity relationships for WA-type withanolides and revealed that WD analogues were less active in both assays compared to their corresponding WA analogues. The 5β,6β-epoxide moiety of withanolides contributed to their cytotoxicity but not HSA. Introduction of a 16β-OAc group to 4,27-di- O-acetyl-WA enhanced cytotoxicity and decreased HSA, whereas introduction of the same group to 4- O-acetyl-WD decreased both activities.

Investigation of Alternaria sp. AST0039, an endophytic fungus obtained from the leaf tissue of Astragalus lentiginosus, led to the isolation of (-)-(10E,15S)-4,6-dichloro-10(11)-dehydrocurvularin (1), (-)-(10E,15S)-6-chloro-10(11)-dehydrocurvularin (2), (-)-(10E,15S)-10(11)-dehydrocurvularin (3), and alterperylenepoxide A (4) together with scytalone and α-acetylorcinol. Structures of 1 and 4 were established from their spectroscopic data, and the relative configuration of 4 was determined with the help of nuclear Overhauser effect difference data. All metabolites were evaluated for their cytotoxic activity and ability to induce heat-shock and unfolded protein responses. Compounds 2 and 3 exhibited cytotoxicity to all five cancer cell lines tested and increased the level of the pro-apoptotic transcription factor CHOP, but only 3 induced the heat-shock response and caused a strong unfolded protein response.

A new metabolite, oxaspirol D (4), together with oxaspirols B (2) and C (3) were isolated from Lecythophora sp. FL1375, an endolichenic fungus isolated from Parmotrema tinctorum, whereas Lecythophora sp. FL1031 inhabiting the lichen Cladonia evansii afforded oxaspirols A (1), B (2), and C (3). Of these, oxaspirol B (2) showed moderate p97 ATPase inhibitory activity. A detailed characterization of all oxaspirols was undertaken because structures proposed for known oxaspirols have involved incomplete assignments of NMR spectroscopic data leading only to their planar structures. Thus, the naturally occurring isomeric mixture (2a and 2b) of oxaspirol B was separated as their diacetates (5a and 5b) and the structures and absolute configurations of 1, 2a, 2b, 3, and 4 were determined by the application of spectroscopic techniques including two-dimensional NMR and the modified Mosher's ester method. Oxaspirol B (2) and its diacetates 5a and 5b were evaluated for their ATPase inhibitory activities of p97, p97 mutants, and other ATP-utilizing enzymes, and only 2 was found to be active, indicating the requirement of some structural features in oxaspirols for their activity. Additional biochemical and cellular assays suggested that 2 was a reversible, non-ATP competitive, and specific inhibitor of p97.

The lichen host, Amandinea medusulina, collected from mangrove habitats in Sri Lanka, and its associated endolichenic fungi were isolated and identified by rDNA-ITS sequence analysis and morphological features. One of the fungal strains frequently isolated from the lichen thalli was identified as Xylaria psidii. This study aimed at the isolation and identification of the cytotoxic compounds present in this fungus. Secondary metabolites of X. psidii were first extracted into ethyl acetate and subsequently subjected to bioassay-guided fractionation to isolate the bioactive compounds. Sulforhodamine B assay against a lung cancer (NCI-H292) cell line was used to determine the differential cytotoxic activity. Bioassay-guided fractionation led to the isolation of an active compound, SS/02/29/08, showing moderate cytotoxicity (IC50 = 27.2 µg/mL). Its structure was elucidated by IR, 1D- and 2D-NMR, and 13C-NMR spectrophotometry and MS, in combination with HRMS, 13C NMR, HSQC, HMBC, and DQF-COSY. The structure of SS/02/29/08 was determined as ( Z)-3-{(3-acetyl-2-hydroxyphenyl)diazenyl}-2,4-dihydroxybenzaldehyde and identified as a new compound. This novel compound has promising differential cytotoxic activity against human lung cancer cell line (NCI-H292).

The Federal Pain Research Strategy recommended development of non-opioid analgesics as a top priority in its strategic plan to address the significant public health crisis and individual burden of chronic pain facing >100 million Americans. Motivated by this challenge, a natural product extracts library was screened and identified a plant extract that targets activity of voltage-gated calcium channels. This profile is of interest as a potential treatment for neuropathic pain. The active extract derived from the desert lavender plant native to southwestern United States, when subjected to bioassay-guided fractionation afforded three compounds identified as pentacyclic triterpenoids, betulinic acid (BA), oleanolic acid, and ursolic acid. BA inhibited depolarization-evoked calcium influx in dorsal root ganglion (DRG) neurons predominantly through targeting low-voltage gated (Cav3 or T-type) and CaV2.2 (N-type) calcium channels. Voltage clamp electrophysiology experiments revealed a reduction of Ca(2+), but not Na(+), currents in sensory neurons following BA exposure. BA inhibited spontaneous excitatory post synaptic currents and depolarization-evoked release of calcitonin gene-related peptide (CGRP) from lumbar spinal cord slices. Notably, BA did not engage human mu, delta, or kappa opioid receptors. Intrathecal administration of BA reversed mechanical allodynia in rat models of chemotherapy-induced peripheral neuropathy (CIPN) and HIV-associated peripheral sensory neuropathy as well as a mouse model of partial sciatic nerve ligation without effects on locomotion. The broad-spectrum biological and medicinal properties reported, including anti-HIV and cancer activities of BA and its derivatives, position this plant-derived small molecule natural product as a potential non-opioid therapy for management of chronic pain.

A new naphthoquinone, teratosphaerone A (1), four new naphthalenones, namely, teratosphaerone B (2), structurally related to 1, iso-balticol B (3), iso-balticol B-4,9-acetonide (4), and (+)-balticol C (5), a new furanonaphthalenone, (3aS,9R,9aS)-1(9a),3(3a),9-hexahydromonosporascone (6), and the known metabolite monosporascone (7) were isolated from Teratosphaeria sp. FL2137, a fungal strain inhabiting the internal tissue of recently dead but undecomposed foliage of Pinus clausa. The structures of 1–6 were elucidated on the basis of their spectroscopic data including 2D NMR, and absolute configurations of 2, 3, and 6 were determined by the modified Mosher’s ester method. When evaluated in a panel of five tumor cell lines, metabolites 1 and 7 isolated from a cytotoxic fraction of the extract exhibited moderate selectivity for metastatic breast adenocarcinoma cell line MDA-MB-231. Of these, 1 showed cytotoxicity to this cell line with an IC50 of 1.2 ± 0.1 μM.

Investigation of aeroponically grown Physalis peruviana resulted in the isolation of 11 new withanolides, including perulactones I-L (1-4), 17-deoxy-23β-hydroxywithanolide E (5), 23β-hydroxywithanolide E (6), 4-deoxyphyperunolide A (7), 7β-hydroxywithanolide F (8), 7β-hydroxy-17-epi-withanolide K (9), 24,25-dihydro-23β,28-dihydroxywithanolide G (10), and 24,25-dihydrowithanolide E (11), together with 14 known withanolides (12-25). The structures of 1-11 were elucidated by the analysis of their spectroscopic data, and 12-25 were identified by comparison of their spectroscopic data with those reported. All withanolides were evaluated for their cytotoxic activity against a panel of tumor cell lines including LNCaP (androgen-sensitive human prostate adenocarcinoma), 22Rv1 (androgen-resistant human prostate adenocarcinoma), ACHN (human renal adenocarcinoma), M14 (human melanoma), SK-MEL-28 (human melanoma), and normal human foreskin fibroblast cells. Of these, the 17β-hydroxywithanolides (17-BHWs) 6, 8, 9, 11-13, 15, and 19-22 showed selective cytotoxic activity against the two prostate cancer cell lines LNCaP and 22Rv1, whereas 13 and 20 exhibited selective toxicity for the ACHN renal carcinoma cell line. These cytotoxicity data provide additional structure-activity relationship information for the 17-BHWs.

Four new nor-spiro-azaphilones, thielavialides A–D (1– 4), a new bis-spiro-azaphilone, thielavialide E (5), together with pestafolide A (6), were isolated from the endophytic fungal strain, Thielavia sp. PA0001, occurring in the healthy leaf tissue of aeroponically grown Physalis alkekengi. The structures and relative configurations of 1–5 were established on the basis of their MS and NMR data. Possible biosynthetic pathways to thielavialides A–E (1– 5) from pestafolide A (6), some involving a Favorskii-like rearrangement, are proposed.

Summary The transcription factor NRF2 confers cellular protection by maintaining cellular redox homeostasis and proteostasis. Basal NRF2 levels are normally low due to KEAP1-mediated ubiquitylation and subsequent proteasomal degradation. KEAP1, a substrate adaptor protein of a KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex, contains a critical cysteine (C151) that is modified by electrophiles or oxidants, resulting in inactivation of the E3 ligase and inhibition of NRF2 degradation. Currently, nearly all NRF2 inducers are electrophilic molecules that possess unwanted off-target effects due to their reactive nature. Here, we report a group of NRF2 inducers, ent-kaurane diterpenoid geopyxins, with and without C151 reactive electrophilic moieties. Among 16 geopyxins, geopyxin F, a non-electrophilic NRF2 activator, showed enhanced cellular protection relative to an electrophilic NRF2 activator, geopyxin C. To our knowledge, this is the first detailed structure-activity relationship study of covalent versus non-covalent NRF2 activators, showing the promise of non-covalent NRF2 activators as potential therapeutic compounds.

Three new alkaloids, phomapyrrolidones A–C (1–3), bearing a cyclopenta[b]fluorene ring system were isolated from the mycelium extract of the endophytic fungal strain, Phoma sp. NRRL 46751, inhabiting Saurauia scaberrinae. Methylation of 1 afforded its N-methyl derivative 4. The planar structures and relative configurations of 1–4 were elucidated by extensive spectroscopic analysis. Phomapyrrolidones B (2) and C (3) exhibited weak antitubercular activity at subcytotoxic concentrations.

O1 IL-15 primes an mTOR-regulated gene-expression program to prolong anti-tumor capacity of human natural killer cells #### Andreas Lundqvist1, Vincent van Hoef1, Xiaonan Zhang1, Erik Wennerberg2, Julie Lorent1, Kristina Witt1, Laia Masvidal Sanz1, Shuo Liang1, Shannon Murray3, Ola Larsson1

In an attempt to explore the biosynthetic potential of the endolichenic fungus Corynespora sp. BA-10763, its metabolite profiles under several culture conditions were investigated. When cultured in potato dextrose agar, it produced three new heptaketides, 9-O-methylscytalol A (1), 7-desmethylherbarin (2), and 8-hydroxyherbarin (3), together with biogenetically related metabolites scytalol A (4), 8-O-methylfusarubin (5), scorpinone (6), and 8-O-methylbostrycoidin (7), which are new to this organism, and herbarin (8), a metabolite previously encountered in this fungal strain. The use of malt extract agar as the culture medium led to the isolation of 6, 8, 1-hydroxydehydroherbarin (9), and 1-methoxydehydroherbarin (10), which was found to be an artifact formed during the extraction of the culture medium with methanol. The structures of all new compounds were determined by interpretation of their spectroscopic data and chemical interconversions.

Five new metabolites, (+)-(5 S,10 S)-4'-hydroxymethylcyclozonarone ( 1), 3-ketotauranin ( 3), 3alpha-hydroxytauranin ( 4), 12-hydroxytauranin ( 5), and phyllospinarone ( 6), together with tauranin ( 2), were isolated from Phyllosticta spinarum, a fungal strain endophytic in Platycladus orientalis. The structures of the new compounds were determined on the basis of their 1D and 2D NMR spectroscopic data and chemical interconversions. All compounds were evaluated for inhibition of cell proliferation in a panel of five cancer cell lines, and only tauranin ( 2) showed activity. When tested in a flow cytometry-based assay, tauranin induced apoptosis in PC-3M and NIH 3T3 cell lines.

In an attempt to uncover the biosynthetic potential of plant-associated fungi, the effect of culture conditions on metabolite production by Paraphaeosphaeria quadriseptata and Chaetomium chiversii was investigated. These studies indicated that the production of the major metabolites by P. quadriseptata differ when the water used to make the media was changed from tap water to distilled water. It resulted in the isolation of six new secondary metabolites, cytosporones F-I ( 1- 4), quadriseptin A ( 5), and 5'-hydroxymonocillin III ( 6) together with monocillin III ( 7), a metabolite new to P. quadriseptata, in addition to monocillin I ( 8), a previously known metabolite from this organism. Aposphaerin B ( 9) encountered was suspected to be an artifact originating from cytosporone F ( 1). Incorporation of heavy metal ions to P. quadriseptata culture medium induced production of monocillin I ( 8) by this fungus. Cultivation of C. chiversii in liquid medium resulted in the isolation of chaetochromin A ( 12) as the major metabolite instead of radicicol ( 10), the major constituent of this organism when grown in a solid medium. Compounds 1- 7 and 12 were evaluated for their potential to inhibit Hsp90 and antiproliferative activity toward the cancer cell lines NCI-H460, MCF-7, and SF-268. Only compounds 6, 7, and 8 exhibited significant activity in both assays.

Precursor-directed biosynthesis was used to produce analogues of the cyclic depsipeptide mycotoxin beauvericin (1) using the filamentous fungus Beauveria bassiana ATCC 7159. Feeding 30 analogues of D-2-hydroxyisovalerate and L-phenylalanine, the natural 2-hydroxycarboxylic acid and amino acid precursors of beauvericin, led to the biosynthesis of novel beauvericins. Six of these were isolated and characterized, and their cytotoxicity and directional cell migration (haptotaxis) inhibitory activity against the metastatic prostate cancer cell line PC-3M were evaluated. Replacement of one, two, or all three of the D-2-hydroxyisovalerate constituents in beauvericin (1) with 2-hydroxybutyrate moieties (beauvericins G1-3, compounds 2-4) caused a parallel decline of cell migration inhibitory activity and cytotoxicity, suggesting a requirement for a branched side chain for both of these biological activities at the corresponding positions of beauvericins. Replacement of one, two, or all three N-methyl-L-phenylalanine residues of beauvericin with N-methyl-L-3-fluorophenylalanine moieties (beauvericins H1-3, compounds 5-7) increased cytotoxicity without affecting antihaptotactic activity.

Prostate cancer (PC) is the second most prevalent cancer among men in Western societies, and those who develop metastatic castration-resistant PC (CRPC) invariably succumb to the disease. The need for effective treatments for CRPC is a pressing concern, especially due to limited durable responses with currently employed therapies. Here, we demonstrate the successful application of a high-throughput gene-expression profiling assay directly targeting genes of the androgen receptor pathway to screen a natural products library leading to the identification of 17β-hydroxywithanolides 1-5, of which physachenolide D (5) exhibited potent and selective in vitro activity against two PC cell lines, LNCaP and PC-3. Epoxidation of 5 afforded physachenolide C (6) with higher potency and stability. Structure-activity relationships for withanolides as potential anti-PC agents are presented together with in vivo efficacy studies on compound 6, suggesting that 17β-hydroxywithanolides are promising candidates for further development as CRPC therapeutics.

In an effort to discover small molecule inhibitors of Hsp90, we have screened over 500 EtOAc extracts of Sonoran desert plant-associated fungi using a two-stage strategy consisting of a primary cell-based heat shock induction assay (HSIA) followed by a secondary biochemical luciferase refolding assay (LRA). Bioassay-guided fractionation of extracts active in these assays derived from Chaetomium chiversii and Paraphaeosphaeria quadriseptata furnished the Hsp90 inhibitors radicicol (1) and monocillin I (2), respectively. In SAR studies, 1, 2, and their analogues, 3-16, were evaluated in these assays, and the antiproliferative activity of compounds active in both assays was determined using the breast cancer cell line MCF-7. Radicicol and monocillin I were also evaluated in a solid-phase competition assay for their ability to bind Hsp90 and to deplete cellular levels of two known Hsp90 client proteins with relevance to breast cancer, estrogen receptor (ER), and the type 1 insulin-like growth factor receptor (IGF-1R). Some inferences on SAR were made considering the crystal structure of the N-terminus of yeast Hsp90 bound to 1 and the observed biological activities of 1-16. Isolation of radicicol and monocillin I in this study provides evidence that we have developed an effective strategy for discovering natural product-based Hsp90 inhibitors with potential anticancer activity.

Bioassay-guided fractionation of a cytotoxic EtOAc extract of Aspergillus flavipes occurring in the rhizosphere of Ericameria laricifolia resulted in the isolation of three new cytochalasans, namely, aspochalasins I (1), J (2), and K (3), and four known cytochalasans, aspochalasins C (4), D (5), and E (6) and TMC-169 (7). The structures of compounds 1-3 were established on the basis of extensive 1D and 2D NMR spectroscopic analysis. All compounds exhibited weak to moderate cytotoxicity against NCI-H460, MCF-7, and SF-268 cancer cell lines, but none showed significant selectivity.

A novel cyclopentenedione, asterredione (1), two new terrecyclic acid A derivatives, (+)-5(6)-dihydro-6-methoxyterrecyclic acid A (2) and (+)-5(6)-dihydro-6-hydroxyterrecyclic acid A (3), and five known compounds, (+)-terrecyclic acid A (4), (-)-quadrone (5), betulinan A (6), asterriquinone D (7), and asterriquinone C-1 (8), were isolated from Aspergillus terreus occurring in the rhizosphere of Opuntia versicolor, using bioassay-guided fractionation. Acid-catalyzed reaction of 2 under mild conditions afforded 4, whereas under harsh conditions 2 yielded 5 and (-)-isoquadrone (9). Catalytic hydrogenation and methylation of 4 afforded 5(6)-dihydro-terrecyclic acid A (10) and (+)-terrecyclic acid A methyl ester (11), respectively. The structures of 1-11 were elucidated by spectroscopic methods. All compounds were evaluated for cytotoxicity in a panel of three sentinel cancer cell lines, NCI-H460 (non-small cell lung cancer), MCF-7 (breast cancer), and SF-268 (CNS glioma), and were found to be moderately active. Cell cycle analysis of 2, 4, and 5 using the NCI-H460 cell line indicated that 4 is capable of disrupting the cell cycle through an apparent arrest to progression at the G(1) and G(2)/M phases in this p53 competent cell line. A pathway for the biosynthetic origin of asterredione (1) from asterriquinone D (7) is proposed.

The structures of three triterpene alcohols isolated from the latex of Euphorbia antiquorum were established to be eupha-7,9(11),24-trien-3beta-ol (2; antiquol C), 19(10-->9)abeo-8alpha,9beta,10alpha-eupha-5,24-dien-3beta-ol (3; antiquol B), and 24-methyltirucalla-8,24(24(1))-dien-3beta-ol (4; euphorbol) on the basis of spectroscopic methods. Compounds 3 and 4 have previously been assigned the erroneous structures of 10alpha-cucurbita-5,24-dien-3alpha-ol and 24-methyleupha-8,24(24(1))-dien-3beta-ol, respectively. Compounds 2-4 and four other known compounds isolated from the latex, euphol (1), lemmaphylla-7,21-dien-3beta-ol (5), isohelianol (6), and camelliol C (7), showed potent inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA).

Four new ent-kaurane diterpenoids, geopyxins A-D (1-4), were isolated from Geopyxis aff. majalis, a fungus occurring in the lichen Pseudevernia intensa, whereas Geopyxis sp. AZ0066 inhabiting the same host afforded two new ent-kaurane diterpenoids, geopyxins E and F (5 and 6), together with 1 and 3. The structures of 1-6 were established on the basis of their spectroscopic data, while the absolute configurations were assigned using modified Mosher's ester method. Methylation of 1-3, 5, and 6 gave their corresponding methyl esters 7-11. On acetylation, 1 and 7 yielded their corresponding monoacetates 12 and 14 and diacetates 13 and 15. All compounds were evaluated for their cytotoxic and heat-shock induction activities. Compounds 2, 7-10, 12, 14, and 15 showed cytotoxic activity in the low micromolar range against all five cancer cell lines tested, but only compounds 7-9, 14, and 15 were found to activate the heat-shock response at similar concentrations. From a preliminary structure-activity perspective, the electrophilic α,β-unsaturated ketone carbonyl motif present in all compounds except 6 and 11 was found to be necessary but not sufficient for both cytotoxicity and heat-shock activation.

Five new isopimarane diterpenes, smardaesidins A – E (1 – 5) and two new 20-nor-isopimarane diterpenes, smardaesidins F (6) and G (7) together with sphaeropsidins A (8), and C – F (10 – 13) were isolated from an endophytic fungal strain, Smardaea sp. AZ0432, occurring in living photosynthetic tissue of the moss Ceratodon purpureus. Of these, smardaesidins B (2) and C (3) were obtained as an inseparable mixture of isomers. Chemical reduction of sphaeropsidin A (8) afforded sphaeropsidin B (9) whereas catalytic hydrogenation of 8 yielded 7-O-15,16-tetrahydrosphaeropsidin A (14), and its new derivative, 7-hydroxy-6-oxo-isopimara-7-en-20-oic acid (15). Acetylation and diazomethane reaction of sphaeropsidin A (8) afforded two of its known derivatives, 6-O-acetylsphaeropsidin A (16) and 8,14-methylenesphaeropsidin A methyl ester (17), respectively. Methylation of 10 yielded sphaeropsidin C methyl ester (18). The planar structures and relative configurations of the new compounds 1 – 7, and 15 were elucidated using MS, and 1D and 2D NMR experiments while the absolute configurations of the stereocenters of 4 and 6 – 8 were assigned using modified Mosher’s ester method, CD spectra, and comparison of specific rotation data with literature values. Compounds 1 – 18 were evaluated for their potential anticancer activity using several cancer cell lines and cells derived from normal human primary fibroblasts. Of these, compounds 8, 11, and 16 showed significant cytotoxic activity. More importantly, sphaeropsidin A (8) showed cell-type selectivity in cytotoxicity assay and inhibited migration of metastatic breast adenocarcinoma (MDA-MB-231) cells at sub-cytotoxic concentrations.

The stem bark of Luvunga angustifolia yielded a new acridone alkaloid, 5-methoxyarborinine [1], and several known compounds. Several known compounds were also isolated from Limonia aridiuima. Pleiospermium alatum afforded a rare coumarin glycoside, apiosylskimmin [5], and two known limonoids 6 and 7. Nmr studies of 6 demonstrated strong nOe effects due to through-space coupling and led to revision of some previous carbon signal assignments

Beauvericin, a cyclohexadepsipeptide ionophore from the entomopathogen Beauveria bassiana, shows antibiotic, antifungal, insecticidal, and cancer cell antiproliferative and antihaptotactic (cell motility inhibitory) activity in vitro. The bbBeas gene encoding the BbBEAS nonribosomal peptide synthetase was isolated from B. bassiana and confirmed to be responsible for beauvericin biosynthesis by targeted disruption. BbBEAS utilizes D-2-hydroxyisovalerate (D-Hiv) and L-phenylalanine (Phe) for the iterative synthesis of a predicted N-methyl-dipeptidol intermediate, and forms the cyclic trimeric ester beauvericin from this intermediate in an unusual recursive process. Heterologous expression of the bbBeas gene in Escherichia coli to produce the 3189 amino acid, 351.9 kDa BbBEAS enzyme provided a strain proficient in beauvericin biosynthesis. Comparative infection assays with a BbBEAS knockout B. bassiana strain against three insect hosts revealed that beauvericin plays a highly significant but not indispensable role in virulence.

Fungal polyketides with the resorcylic acid lactone (RAL) scaffold are of interest for growth stimulation, the treatment of cancer, and neurodegenerative diseases. The RAL radicicol is a nanomolar inhibitor of the chaperone Hsp90, whose repression leads to a combinatorial blockade of cancer-causing pathways. Clustered genes for radicicol biosynthesis were identified and functionally characterized from the endophytic fungus Chaetomium chiversii, and compared to recently described RAL biosynthetic gene clusters. Radicicol production is abolished upon targeted inactivation of a putative cluster-specific regulator, or either of the two polyketide synthases that are predicted to collectively synthesize the radicicol polyketide core. Genomic evidence supports the existence of flavin-dependent halogenases in fungi: inactivation of such a putative halogenase from the C. chiversii radicicol locus yields dechloro-radicicol (monocillin I). Inactivation of a cytochrome P450 epoxidase furnishes pochonin D, a deepoxy-dihydro radicicol analog.

Two new heptaketides, corynesporol (1) and 1-hydroxydehydroherbarin (2), along with herbarin (3) were isolated from an endolichenic fungal strain, Corynespora sp. BA-10763, occurring in the cavern beard lichen Usnea cavernosa. The structures of 1-3 were elucidated from their spectroscopic data. Aerial oxidation of corynesporol (1) yielded herbarin (3). Acetylation of 1 afforded the naphthalene derivative 4, whereas acetylation of 3 gave the corresponding naphthoquinone 6 and dehydroherbarin (5). All compounds were evaluated for their cytotoxicity and ability to inhibit migration of human metastatic breast and prostate cancer cell lines MDA-MB-231 and PC-3M, respectively. Dehydroherbarin (5) inhibited migration of both cell lines at concentrations not toxic to these cell lines. This is the first report of metabolites from an endolichenic fungus.

In continuing our search for bioactive and/or novel secondary metabolites from endosymbiotic microorganisms of the Sonoran desert [1], we have investigated an EtOAc extract derived from the solid (potato dextrose agar, PDA) culture of the endophytic fungal strain, Pulvinula sp. 11120, aff. Pulvinula archeri (Pyronemataceae, Pezizoymycetes, Pezizomycotina, Ascomycota) isolated from the healthy leaf tissue of the Arizona cypress, Cupressus arizonica (Cupressaceae). Herein we report the isolation and structure elucidation of three new natural furanone metabolites, pulvinulin A (1), graminin C (2), and cis-gregatin B (3), together with graminin B (4), and 10-norparvulenone (5) from Pulvinula sp. 11120 (Figure 1). This constitutes the first report of metabolites from a fungal strain of the genus Pulvinula. 10-Norparvulenone (5) with antiinfluenza viral activity [2] has previously been reported from an endophyte of a mangrove plant [3]. Figure 1 Structures of pulvinulin A (1), graminin C (2), cis-gregatin B (3), graminin B (4), and 10-norparvulenone (5) from Pulvinula sp. 11120. Natural furanones constitute a rare and a comparatively small class of biologically active fungal metabolites previously encountered in the fungal genera, Aspergillus [4,5], Cephalosporium [6], and Penicillium [7]. Despite its simplicity, the central core of these metabolites has undergone several structural revisions over the past three decades. The core structure, 3-acyl-4-methoxyfuran-2(3H)-one, the first proposed for these metabolites [8,9], was later revised to 4-acyl-3-methoxyfuran-3(2H)-one [10], and finally to the currently accepted 4-(methoxycarbonyl)furan-3(2H)-one [11]. Several fungal-derived furanones have been reported to have phytotoxic [12], antibacterial and antifungal activities [9] and implicated as the causal agents of stripe disease of wheat [12] and brown stem rot of adzuki beans [9]. Pulvinulin A (1), [α]D25 +108, was obtained as a colorless oil, the molecular formula of which was determined to be C18H28O4 on the basis of its HRESIMS (m/z 331.1851 [M+Na]+; calcd 331.1880), accounting for five degrees of unsaturation. 1H and 13C NMR spectra together with HSQC data of 1 indicated the presence of a tertiary methyl [δH 1.37 (s); δC 21.6], two primary methyls, one methoxyl, five methylenes, two methines of which one is oxygenated [δH 3.28 (d, J = 10.4 Hz); δC 75.9], four olefinics, an oxygenated quaternary carbon (δC 83.6), one ketone carbonyl carbon (δC 208.3) and an ester carbonyl carbon (δC 167.6). The presence of two spin systems, CH3CH2CH2CH2CH2CH(O)CH– and CH3CH2CH=CH–CH=CH– in 1 was evident from its 1H–1H COSY data (Figure 2). The connectivity of these spin systems, tertiary methyl, methoxycarbonyl, and non-protonated carbons was established by analysis of the HMBC data (Figure 2). HMBC correlations of H-1'/C-4 and H-1'/C-5 established the connectivity between C-5 and C-1'. Tertiary methyl protons (δH 1.37) showed HMBC correlations to the ketone carbonyl (C-4) and C-1' placing the tertiary methyl at C-5. HMBC correlations of H-3/C-4, H-2/C-3, and H-2/C-4 established the connectivity between C-3 and C-4. Placement of the methoxycarbonyl group at C-3 was supported by the HMBC correlations of H-2 and H-3 to each other and to this carbonyl carbon (C-1'"). Since two double bonds, and ketone and ester carbonyls accounted for four degrees of unsaturation, 1 should possess a monocyclic framework. Based on its molecular formula and the presence of a ketone and an ester functionality accounting for 3 of the 4 oxygen atoms in 1 suggested that the two oxygenated carbons C-2 and C-5 were linked to each other through a common oxygen atom to form a furan ring system. The E configuration for Δ1',2' and the Z configuration for Δ3',4' double bonds in 1 were assigned based on their 3JHH values of 15.2 Hz and 11.2 Hz, respectively. These data indicated that 1 possessed a structure similar to that of graminin B (4), also encountered in this study (see below) and recently reported as a metabolite of the fungus, Paraconiothyrium sp. [13]. The only difference between 1 and 4 was found to be the absence of a Δ2,3 double bond in 1. Thus, 1 was suspected to be a 2,3-dihydro derivative of graminin B. The ROESY spectrum of 1 showed cross peaks among 5-CH3, H-2 and H-3 suggesting that these have co-facial orientation (Figure 1). Catalytic hydrogenation (H2/Pd-C) and acetylation (Ac2O/pyridine) of pulvinulin A (1) afforded its tetrahydro derivative 6 and the enol acetate 7 (Figure 3), respectively, further supporting the proposed structure 1 for this metabolite. The absolute configuration of the only chiral center (C-5) in graminin B (4) was assumed to be R by comparison of its [α]D data with known furanones [13]. However, the presence of three chiral centers (C-2, C-3, and C-5) in pulvinulin A (1) precluded the use of its [α]D value for this purpose. Biosynthetically, 1 may share a common pathway with 2–4 co-occurring in Pulvinula sp. 11120 suggesting that these would bear the same absolute configuration at C-5. Since 2–4 have been determined to have R configuration at C-5 (see below), pulvinulin A (1) may be assumed to have the same absolute configuration at this position. Thus, the structure of pulvinulin A was established as methyl (2S,3R,5R)-5-[(1'E,3'Z)-hexa-1,3-dienyl]-5-methyl-4-oxo-2-pentyl-2,3,4,5-dihydrofuran-3 carboxylate (1). Figure 2 1H–1H COSY, and selected HMBC and ROESY correlations of 1. Figure 3 Structures of chemical transformation products 6–9 obtained from metabolites 1–3. Metabolite 2, [α]D25 +159, was obtained as a colorless oil. A molecular formula of C18H24O4 was determined for 2 on the basis of its HRESIMS (m/z 305.1746 [M+H]+, calcd C18H25O4: 305.1747) and 13C NMR data, accounting for seven degrees of unsaturation. The 1H and 13C NMR data of 2 were almost identical with those of graminin B (4) [13] except that 2 contained an additional double bond which was placed at C-1"(2") based on its NMR data (see Experimental). Because of its structural relationship to graminin B (4), metabolite 2 was given the trivial name graminin C. Catalytic hydrogenation of 2 afforded 8 (Figure 3), which was shown to be identical with the hydrogenation product of 4, further supporting their structural relationship. The optical rotation value of 8 ([α]D25 −64) was found to be almost identical to that of the hydrogenation product of 4 ([α]D25 −61) suggesting both 2 and 4 may be assumed to have the same absolute configuration at the only chiral center (C-5) of these molecules. Since the absolute configuration at C-5 of 4 has been assumed to be R [13], the absolute configuration at C-5 of 2 may tentatively be assigned as R. Thus, the structure of graminin C was established as methyl (5R)-5-[(1'E,3'Z)-hexa-1,3-dienyl]-5-methyl-4-oxo-2-[(E)-pent-1-enyl]-4,5-dihydrofuran-3 carboxylate (2). Comparison of the 1H and 13C NMR data of the metabolite 3, [α]D25 +168, with those reported for synthetic cis-gregatin B [11] suggested that they are identical with each other. The absolute configuration at the only chiral center (C-5) in synthetic 3 was established as R based on the absolute configuration of the starting materials used for its synthesis, but its [α]D value has not been determined due to the lack of sufficient material [11]. Catalytic hydrogenation of 3 afforded its new derivative, 1'(2'),3'(4')- tetrahydro-gregatin B (9) (Figure 3), [α]D25 −57. Metabolites 4 and 5 were identified as graminin B [13] and 10-norparvulenone [3] by comparison of their spectroscopic data with those reported. Antimicrobial activity of furanones 1–4 against Escherichia coli ATCC 25922 was evaluated using the agar diffusion method [14]. Diameters of the inhibition zones were measured after incubation for 24 h at 37°C. Ampicillin was used as the positive control. The activity data (Table 1) suggested that the antibacterial activity of these metabolites depended on the number of double bonds that are in conjugation with the carbonyl moiety of the furanone ring. Table 1 Antibacterial activity of metabolites 1–4 against E. coli ATCC 25922.

Three new esters of orsellinic acid, globosumones A-C (1-3), and three known compounds, orsellinic acid (4), orcinol, and trichodion (5), were isolated from Chaetomium globosum endophytic on Ephedrafasciculata (Mormon tea). The structures of the new compounds 1-3 were established spectroscopically, which included 2D NMR experiments and 1H NMR studies on Mosher's ester derivatives. All compounds were evaluated for inhibition of cell proliferation in a panel of four cancer cell lines, NCI-H460 (non-small cell lung cancer), MCF-7 (breast cancer), SF-268 (CNS glioma), and MIA Pa Ca-2 (pancreatic carcinoma), and normal human fibroblast cells (WI-38). Only globosumones A (1) and B (2) were found to be moderately active.

Antiangiogenic activity has been identified in an aqueous EtOH extract of Rabdosia rubescens, a component of the dietary supplement PC SPES. Bioassay-guided fractionation using a novel in vitro human endothelial cell-based assay for angiogenesis afforded the diterpenoids ponicidin (1) and oridonin (2), with significant antiangiogenic activity at subcytotoxic concentrations, suggesting that these constituents may strongly contribute to the demonstrated clinical efficacy of PC SPES as a treatment for advanced prostate cancer.

Made available in DSpace on 2022-04-29T08:47:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-01-01 Southwest Ctr. for Nat. Prod. Res. Office of Arid Lands Studies University of Arizona, 250 E. Valencia Road, Tucson, AZ 85706-6800 Instituto de Quimica Universidade Estadual Paulista, CP. 335, 14800-90 Araraquara, SP Departmento de Quimica Universidade Federal de Minas Gerais, Belo Horizonte Div. of Plant Pathology/Microbiology Department of Plant Sciences University of Arizona, Tucson, AZ 85721-0036 Pediatric Hematology/Oncology Steele Memorial Children's Res. Ctr. University of Arizona, Tucson, AZ 85724 Instituto de Quimica Universidade Estadual Paulista, CP. 335, 14800-90 Araraquara, SP

The biotransformation of the clerodane diterpene, 3,12-dioxo-15,16-epoxy-4-hydroxy-cleroda-13(16),14-diene (1), obtained from Croton micans var. argyroglossum (Baill.) Müll., was investigated for the first time. Whole cells of Cunninghamella echinulata and Rhizopus stolonifer were used as enzymatic systems, and with both fungi the only biotransformation product obtained was the new ent-neo-clerodane diterpene (3 R,4 S,5 S,8 S,9 R,10 S)-3,4-dihydroxy-15,16-epoxy-12-oxo-cleroda-13(16),14-diene (2a). The absolute stereochemistry of 2a was inferred by comparison of its optical rotation with those of the chemical reduction product of 1 and its quasienantiomer 2c.

A new ascochlorin, 10′-deoxy-10′ α-hydroxyascochlorin (1), together with ascofuranone (2), ascochlorin (3), and 4′,5′-dihydro-4′ β-hydroxyascochlorin (4) were isolated from Acremonium sp. LG0808, an endophytic fungal strain occurring in the stem tissue of the medicinal plant, Ephedra trifurca. The structure of 1 was elucidated on the basis of its high-resolution mass spectrometric, and 1D and 2D NMR spectroscopic data. Compounds 1 and 3 inhibited migration of metastatic prostate cancer cells, PC-3M. In addition, 3 exhibited moderately selective cytotoxicity against the NCI-H460 (non-small cell lung cancer) cell line, but its dimethyl ether (6) showed selective activity against PC-3M, MCF-7 (breast cancer), and MDA-MB-231 (metastatic breast cancer) cell lines.

Biotransformation of monocillin I (1) by Beauveria bassiana ATCC 7159 was investigated. Two new derivatives 2 and 3 were isolated and identified on the basis of the spectroscopic data. Compounds 2 and 3 are synthesized by hydration at 10,11-double bond and hydrolysis of 14,15-epoxide, respectively. The R configuration of 11-OH in 2 was established by the modified 2-methoxy-2-trifluoromethylphenylacetic acid (MTPA) method. The conversion of 1 to 2 and 3 was reconstituted in an acid solution, indicating that the formation of 2 and 3 is an acid-catalyzed instead of an enzymatic process.

Isolation and structure elucidation of a new limonoid, acidissimin, from the stem bark and a known limonoid, obacunone, from the root bark of Limonia acidissima