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Analysis of the genome sequence of Streptomyces sp. KCB13F003 showed the presence of a cryptic gene cluster encoding flavin-dependent halogenase and nonribosomal peptide synthetase. Pleiotropic approaches using multiple culture media followed by LC-MS-guided isolation and spectroscopic analysis enabled the identification of two new chlorinated cyclic hexapeptides, ulleungmycins A and B (1 and 2). Their structures, including absolute configurations, were determined by 1D and 2D NMR techniques, advanced Marfey's analysis, and GITC derivatization. The new peptides, featuring unusual amino acids 5-chloro-l-tryptophan and d-homoleucine, exhibited moderate antibacterial activities against Gram-positive pathogenic bacteria including methicillin-resistant and quinolone-resistant Staphylococcus aureus.

The methanol extract of the roots and stems of Daphne genkwa and its constituents yuanhuacin (1) and genkwanine N were previously reported to have Nurr1 activating effects and neuroprotective effects in an animal model of Parkinson's disease (PD). In this study, four more daphnane-type diterpenes (acutilonine F (2), wikstroemia factor M1 (3), yuanhuadine (5), and yuanhuatine (6)) and two phorbol-type diterpenes (prostratin Q (4) and 12-O-n-deca-2,4,6-trienoyl-phorbol-(13)-acetate (7)) were isolated as Nurr1 activating compounds from the D. genkwa extract. Consistent with their higher Nurr1 activating activity, compounds 1, 4, 5, and 7 exhibited higher inhibitory activity on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in murine microglial BV-2 cells with an IC50 (µM) of 1-2, which was 15-30 times more potent than that of minocycline (29.9 µM), a well-known anti-neuroinflammatory agent. Additionally, these diterpenes reduced expression and transcription of LPS-induced pro-inflammatory cytokines in BV-2 cells. Thus, the daphnane-type and phorbol-type diterpenes had anti-neuroinflammatory activity with Nurr1 activation and could be responsible for the anti-PD effect of the roots and stems of D. genkwa.

Two new potent anti-Gram negative compounds, coralmycins A (1) and B (2), were isolated from cultures of the myxobacteria Corallococcus coralloides M23, together with another derivative (3) that was identified as the very recently reported cystobactamid 919-2. Their structures including the relative stereochemistry were elucidated by interpretation of spectroscopic, optical rotation, and CD data. The relative stereochemistry of 3 was revised to "S*R*" by NMR analysis. The antibacterial activity of 1 was most potent against Gram-negative pathogens, including Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanii, and Klebsiella pneumoniae, with MICs of 0.1-4 μg/mL; these MICs were 4-10 and 40-100 times stronger than the antibacterial activities of 3 and 2, respectively. Thus, these data indicated that the β-methoxyasparagine unit and the hydroxy group of the benzoic acid unit were critical for antibacterial activity.

Three cyclic lipopeptides, including one known (1) and two new (2 and 3) compounds, that possess the rare enamide linkage group were discovered from Streptomyces sp. KCB14A132, an actinobacterium isolated from a soil sample collected from Jeung Island, Korea. The NMR and MS-based characterization showed that they differed in the amino acid residues in the peptide backbone. Application of Marfey's analysis, GITC derivatization, and modified Mosher's method, as well as ECD measurements provided the absolute configurations of enamidonin (1) and those of new compounds enamidonins B and C (2 and 3). The two new enamidonin analogues were shown to exhibit antibacterial activity against Gram-positive bacteria including methicillin-resistant and quinolone-resistant Staphylococcus aureus. Furthermore, evaluation of the extraction conditions and a close inspection of the LC-MS chromatograms revealed that the N, N-acetonide unit of the enamidonin family was formed during the acetone extraction process. The chemically prepared deacetonide derivatives of enamidonins were found to lack antibacterial activity, demonstrating that the dimethylimidazolidinone residue is necessary for antibacterial activity.

Parkinson's disease (PD), primarily caused by selective degeneration of midbrain dopamine (mDA) neurons, is the most prevalent movement disorder, affecting 1-2% of the global population over the age of 65. Currently available pharmacological treatments are largely symptomatic and lose their efficacy over time with accompanying severe side effects such as dyskinesia. Thus, there is an unmet clinical need to develop mechanism-based and/or disease-modifying treatments. Based on the unique dual role of the nuclear orphan receptor Nurr1 for development and maintenance of mDA neurons and their protection from inflammation-induced death, we hypothesize that Nurr1 can be a molecular target for neuroprotective therapeutic development for PD. Here we show successful identification of Nurr1 agonists sharing an identical chemical scaffold, 4-amino-7-chloroquinoline, suggesting a critical structure-activity relationship. In particular, we found that two antimalarial drugs, amodiaquine and chloroquine stimulate the transcriptional function of Nurr1 through physical interaction with its ligand binding domain (LBD). Remarkably, these compounds were able to enhance the contrasting dual functions of Nurr1 by further increasing transcriptional activation of mDA-specific genes and further enhancing transrepression of neurotoxic proinflammatory gene expression in microglia. Importantly, these compounds significantly improved behavioral deficits in 6-hydroxydopamine lesioned rat model of PD without any detectable signs of dyskinesia-like behavior. These findings offer proof of principle that small molecules targeting the Nurr1 LBD can be used as a mechanism-based and neuroprotective strategy for PD.

Dihydrofolate reductase (DHFR) has been confirmed to be a novel target for antibacterial drug development. In this study, we determined that a fungal metabolite from Stachybotrys sp. FN298 can inhibit the DHFR of Staphylococcus aureus. Its structure was identified as a lactone form of stachybotrydial using mass spectrometry and nuclear magnetic resonance analysis. This compound inhibited S. aureus DHFR with a half-maximal inhibitory concentration of 41 µM. It also prevented the growth of S. aureus and methicillin-resistant S. aureus (MRSA) with a minimum inhibitory concentration of 32 µg·mL(-1). To our knowledge, this is the first description of a DHFR inhibitor of microbial origin. The inhibitory function of the lactone form of stachybotrydial highlights its potential for development into a new broad-spectrum antibacterial agent and as an agent against MRSA.

Nurr1 is an orphan nuclear receptor that is essential for the differentiation and maintenance of dopaminergic neurons in the brain, and it is a therapeutic target for Parkinson’s disease (PD). During the screening for Nurr1 activators from natural sources using cell-based assay systems, a methanol extract of the combined stems and roots of Daphne genkwa was found to activate the transcriptional function of Nurr1 at a concentration of 3 μg/mL. The active components were isolated and identified as genkwanine N (1) and yuanhuacin (2). Both compounds 1 and 2 significantly enhanced the function of Nurr1 at 0.3 μM. Nurr1-specific siRNA abolished the activity of 1 and 2, strongly suggesting that transcriptional activation by 1 and 2 occurred through the modulation of Nurr1 function. Additionally, treatment with 1 and 2 inhibited 6-hydroxydopamine (6-OHDA)-induced neuronal cell death and lipopolysaccharide (LPS)-induced neuroinflammation. Moreover, in a 6-OHDA-lesioned rat model of PD, intraperitoneal administration of 2 (0.5 mg/kg/day) for 2 weeks significantly improved behavioral deficits and reduced tyrosine hydroxylase (TH)-positive dopaminergic neuron death induced by 6-OHDA injection and had a beneficial effect on the inflammatory response in the brain. Accordingly, compounds 1 and 2, the first reported Nurr1 activators of natural origin, are potential lead compounds for the treatment of PD.

Flavimycins A (1) and B (2), novel dimeric 1,3-dihydroisobenzofurans, were isolated as inhibitors of peptide deformylase from cultures of Aspergillus flavipes. Their chemical structures were established by NMR and MS data analysis. Compounds 1 and 2 exist as epimeric mixtures at C-1 through fast hemiacetal-aldehyde tautomerism. Compounds 1 and 2 inhibited Staphylococcus aureus peptide deformylase with IC₅₀ values of 35.8 and 100.1 μM, respectively. Consistent with their PDF inhibition, 1 showed two times stronger antibacterial activity than 2 on S. aureus including MRSA, with MIC values of 32-64 μg/mL.

Bacterial enoyl-acyl carrier protein (ACP) reductase has been confirmed as a novel target for antibacterial drug development. In the screening of inhibitors of Staphylococcus aureus enoyl-ACP reductase (FabI), we found that a methanol extract of leaves of Morus alba L. potently inhibited S. aureus FabI as well as growth of S. aureus. The active principles were identified as chalcomoracin and moracin C by MS and NMR analysis. Chalcomoracin and moracin C inhibited S. aureus FabI with IC(50) of 5.5 and 83.8 µM, respectively. They also prevented the growth of S. aureus with minimum inhibitory concentration (MIC) of 4 and 32 µg/mL, respectively. Consistent with their inhibition against FabI and bacterial growth, they prevented (14)C]acetate incorporation into fatty acid in S. aureus while didn't affect protein synthesis. In this study, we reported that chalcomoracin and moracin C, potent antibacterial compounds from Morus alba, inhibited FabI and fatty acid synthesis.

Bacterial enoyl-ACP reductase (FabI) has been validated as a novel antibacterial target for tackling infections caused by multidrug-resistant pathogens. A few FabI inhibitors, however, are known. This study isolated a new FabI inhibitor from Penicillium sp.A screening programme led to the selection of a Penicillium sp. producing a strong FabI-inhibitory metabolite. The chemical structure of the isolated FabI inhibitor was elucidated by mass spectrometry and nuclear magnetic resonance spectral data. The antibacterial target of the inhibitor was validated by overexpression assays.The isolated FabI inhibitor was elucidated to be vinaxanthone. It selectively inhibited Staphylococcus aureus FabI with an IC(50) of 0.9 microM; it did not affect FabK, an enoyl-ACP reductase of Streptococcus pneumoniae. Consistent with its inhibition of FabI, the inhibitor prevented intracellular fatty acid synthesis while it did not affect protein biosynthesis. It also prevented the growth of S. aureus as well as methicillin-resistant S. aureus (MRSA) and quinolone-resistant S. aureus. Importantly, fabI-overexpressing S. aureus showed reduced susceptibility to the inhibitor compared with the wild-type strain, demonstrating that its antibacterial action is mediated by inhibition of FabI.Vinaxanthone is a new FabI-directed antibacterial of natural origin that could have potential for further development as a new anti-MRSA agent.

Bacterial enoyl-acyl carrier protein (ACP) reductase has been confirmed as a novel target for antibacterial drug development. In this study, we determined that a fungal metabolite from Sporothrix sp. FN611 potently inhibited the enoyl-ACP reductase (FabI) of Staphylococcus aureus. Its structure identified the metabolite as aquastatin A by the MS and NMR data. Aquastatin A inhibited S. aureus FabI with an IC(50) of 3.2 microM. It also prevented the growth of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration of 16-32 microg/ml. Aquastatin A also exerted an inhibitory effect against the FabK isoform, an enoyl-ACP reductase of Streptococcus pneumoniae, with an IC(50) of 9.2 microM. The degalactosylation of aquastatin A did not affect the FabI and FabK-inhibitory or antibacterial activities, thereby suggesting that the sugar moiety within its molecular structure was not involved in these activities. The inhibitory effects of aquastatin A and its degalactosylated derivative on enoyl-ACP reductases and bacterial viability are reported for the first time in this study; these effects point to the potential that aquastatin A may be developed into a new broad-spectrum antibacterial and anti-MRSA agent.

In the course of screening for inhibitors of Staphylococcus aureus peptide deformylase, four new glycosylated macrolactin compounds, macrolactins O ( 1), P ( 2), Q ( 3), and R ( 4), along with the known macrolactins B ( 5) and C ( 6), have been isolated from the liquid cultures of Bacillus sp. AH159-1. The structures of compounds 1- 4 were assigned on the basis of MS and NMR data. They inhibited S. aureus peptide deformylase and also showed antibacterial activity against Escherichia coli and Staphylococcus aureus.

We investigated the protective activity of radicicol, an antifungal antibiotic, against inflammation-induced neurotoxicity in neuron-glia cultures. Radicicol potently prevented the loss of neuronal cell bodies and neurites from LPS/IFN-gamma-induced neurotoxicity in rat cortical neuron-glia cultures with an EC(50) value of 0.09 microM. Radicicol inhibited the LPS/IFN-gamma-induced expression of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) in microglia. Additionally, radicicol decreased the LPS/IFN-gamma-induced release of tumor necrosis factor-alpha (TNF-alpha) in the cultures. The inhibitory potency of radicicol against the production of NO and TNF-alpha was well correlated with the protection of neurons. These results suggest that the protective effect of radicicol against LPS/IFN-gamma-induced neuronal cell death in neuron-glia cultures is mediated via the inhibition of TNF-alpha release, as well as the suppression of iNOS expression in microglia.

Verrulactones D and E with unprecedented skeletons, new inhibitors of Staphylococcus aureus enoyl-ACP reductase, from Penicillium verruculosum F375

Bacterial enoyl-acyl carrier protein (ACP) reductase has been confirmed as a novel target for antibacterial drug development. In the screening of inhibitors of Staphylococcus aureus enoyl-ACP reductase (FabI), complestatin was isolated as a potent inhibitor of S. aureus FabI together with neuroprotectin A and chloropeptin I from Streptomyces chartreusis AN1542. Complestatin and related compounds inhibited S. aureus FabI with IC₅₀ of 0.3-0.6 µM. They also prevented the growth of S. aureus as well as methicillin-resistance S. aureus (MRSA) and quinolone-resistant S. aureus (QRSA), with minimum inhibitory concentrations (MICs) of 2-4 µg/mL. Consistent with its FabI-inhibition, complestatin selectively inhibited the intracellular fatty acid synthesis in S. aureus, whereas it did not affect the macromolecular biosynthesis of other cellular components, such as DNA, RNA, proteins, and the cell wall. Additionally, supplementation with exogenous fatty acids reversed the antibacterial effect of complestatin, demonstrating that it targets fatty acid synthesis. In this study, we reported that complestatin and related compounds showed potent antibacterial activity via inhibiting fatty acid synthesis.

Three new epidithiodioxopiperazine compounds, bionectins A (1), B (2), and C (3), along with a known compound, verticillin D (4), have been isolated from the mycelium of liquid fermentation cultures of the fungus Bionectra byssicola F120. The structures of compounds 1-3 were assigned on the basis of MS and NMR data. Compounds 1 and 2 incorporate a dioxopiperazine moiety with a disulfide bridge in their molecules, while 3 contains a dioxopiperazine ring with two methylsulfanyl groups. Compounds 1 and 2 exhibited antibacterial activity against S. aureus including methicillin-resistant S. aureus (MRSA) and quinolone-resistant S. aureus (QRSA), with MIC values of 10-30 microg/mL, while 3 showed no antibacterial activity even at 100 microg/mL.

In our screening program for new antifungal agents from microbial secondary metabolites, we isolated two new isoflavonol glycosides, genistein 7-alpha-L-6-deoxy-talopyranoside (talosin A) and genistein 4',7-di-alpha-L-6-deoxy-talopyranoside (talosin B), from the culture broth of Kitasatospora kifunensis MJM341. The talosins exhibited strong antifungal activity against Candida albicans, Aspergillus niger and Cryptococcus neoformans with minimal inhibitory concentrations (MIC) in the range of 3- 15 microg/ml while genistein and genistein-7-glucopyranoside did not show antifungal activity at 100 microg/ml. These talosins are the first isoflavonol glycosides with a 6-deoxy-talose sugar component and they may be useful as antifungal agents with low toxicity because of no visible cytotoxicity against the human hepatic HepG2 cell.

Terrein is a bioactive fungal metabolite whose effects are almost unknown. In this study, we found for the first time that terrein has a strong hypopigmentary effect in a spontaneously immortalized mouse melanocyte cell line, Mel-Ab. Treatment of Mel-Ab cells with terrein (10-100 microM) for 4 days significantly reduced melanin levels in a dose-dependent manner. In addition, terrein at the same concentration also reduced tyrosinase activity. We then investigated whether terrein influences the extracellular signal-regulated protein kinase (ERK) pathway and the expression of microphthalmia-associated transcription factor (MITF), which is required for tyrosinase expression. Terrein was found to induce sustained ERK activation and MITF down-regulation, and luciferase assays showed that terrein inhibits MITF promoter activity in a dose-dependent manner. To elucidate the correlation between ERK pathway activation and a decreased MITF transcriptional level, PD98059, a specific inhibitor of the ERK pathway, was applied before terrein treatment and found to abrogate the terrein-induced MITF attenuation. Terrein also reduced the tyrosinase protein level for at least 72 h. These results suggest that terrein reduces melanin synthesis by reducing tyrosinase production via ERK activation, and that this is followed by MITF down-regulation.

New melanin synthesis inhibitors, melanocins A, B and C, were isolated from the fermentation broth and mycelium extract of Eupenicillium shearii F80695. Melanocin A, an isocyanide compound, inhibited mushroom tyrosinase and melanin biosynthesis of B16 melanoma cells with IC50 value of 9.0 nM and MIC value of 0.9 microM, respectively. Melanocin A also inhibited growth of Streptomyces bikiniensis. While, the structurally very related but non-isocyanide compounds melanocins B and C did not show inhibitory activity in these assays. Melanocins A, B and C showed potent antioxidant activity with scavenging activity of DPPH radical and superoxide anion radical.

Benzastatin C, a 3-chloro-tetrahydroquinolone alkaloid from Streptomyces nitrosporeus, showed antiviral activity in a dose-dependant manner with EC50 values of 1.92, 0.53, and 1.99 microg/ml against herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and vesicular stomatitis virus (VSV), respectively. In contrast, benzastatin D, the corresponding dechlorinated derivative, did not exhibit any antiviral activity. These results indicate that the antiviral activity of benzastatin C is mediated, in part, due to the chlorine moiety in its molecular structure.

The structures of benzastatins A, B, C, and D, new free radical scavengers, were determined by spectroscopic studies. Benzastatins A and B incorporate the para-aminobenzamide unit which is rare in fungal metabolites. Benzastatins C and D are unique alkaloids related to virantmycin; they contain the tetrahydroquinoline unit in the molecules.

Objectives The aim was to search for inhibitors of melanogenesis from natural resources. Methods The inhibitory effect of silymarin on melanogenesis in a spontaneously immortalized mouse melanocyte cell line, Mel-Ab, was studied. Key findings Silymarin significantly prevented melanin production in a dose-dependent manner with an IC50 value (concentration producing 50% maximal inhibition) of 28.2 μg/ml, without effects on cell viability. Also, silymarin inhibited l-DOPA oxidation activity of tyrosinase, the rate-limiting melanogenic enzyme, in cell based-systems but it did not directly affect cell-free tyrosinase activity. Furthermore, Western blot analysis indicated that silymarin decreased the expression of tyrosinase protein. Conclusions This study suggests that the depigmenting effect of silymarin might be attributable to inhibition of tyrosinase expression and that silymarin may be useful as a natural skin-lightening agent.

Isodeoxyhelicobasidin, a novel human neutrophil elastase inhibitor from the culture broth of Volvariella bombycina

In the course of screening for FabG inhibitors from microbial sources, a new 24-membered ring lactone named macrolactin S, along with the known compound macrolactin B, has been isolated from the mycelium of liquid fermentation cultures of Bacillus sp. AT28. The structure of macrolactin S was determined on the basis of MS and NMR data. Macrolactin S showed a dose-dependent inhibition of Staphylococcus aureus FabG, not inhibiting S. aureus FabI. Also macrolactin S inhibited the growth of S. aureus, Bacillus subtilis, and Escherichia coli.

A new tetracycline-type antibiotic named viridicatumtoxin B along with the known compound viridicatumtoxin has been isolated from the mycelium of liquid fermentation cultures of Penicillium sp. FR11. The structure of viridicatumtoxin B was determined on the basis of MS and NMR data. Viridicatumtoxin B inhibited the growth of Staphylococcus aureus including methicillin-resistant S. aureus and quinolone-resistant S. aureus with MIC (microg/ml) of 0.5, which is similar with that of vancomycin, but 8-64 times higher activity than that of tetracycline.

A new epidithiodioxopiperazine compound named verticillin G along with the known compound verticillin D has been isolated from the mycelium of liquid fermentation cultures of a fungal strain Bionectra byssicola F 120. The structure of verticillin G was determined on the basis of MS and NMR data. Verticillin G inhibited the growth of Staphylococcus aureus including methicillin-resistant and quinolone-resistant S. aureus with MIC (microg/ml) of 3-10.

Dimerization of inducible NOS has been known to be a potential therapeutic target for iNOS-mediated pathologies. Cyclic dipeptides are among the simplest peptides commonly found as by-products of food processing or metabolites of microorganisms. In this study, we found that cyclo(dehydrohistidyl- l -tryptophyl) (CDHT), a cyclic dipeptide from an unidentified fungal strain Fb956, prevents iNOS dimerization in activated microglial BV-2 cells. CDHT inhibited NO production with an IC50 of 6.5 μM in LPS-treated BV-2 cells. Western blot analysis and iNOS activity measurement of fractions from size-exclusion chromatography of cell lysates indicated that CDHT inhibits dimerization of iNOS, while it has no effect on iNOS expression or enzyme activity. The CDHT inhibition of iNOS dimerization was confirmed by partially denaturing SDS-PAGE analysis. In contrast, CDHT did not affect cGMP production in endothelial HUVEC cells, which indicates no inhibition of endothelial NOS activity. These results reveal that CDHT, one of the simplest and cyclic dipeptides, selectively inhibits NO production by inhibiting iNOS dimerization, and could be a useful therapeutic agent for inflammation-mediated diseases.

Two potent inhibitors of FabK, the enoyl-acyl carrier protein (ACP) reductase of Streptococcus pneumoniae, were isolated from the solid state fermentation of an unidentified fungus F010248. Their structures were identified to be atromentin and leucomelone by various spectral analysis. Atromentin and leucomelone inhibited the FabK with IC50 values of 0.24 and 1.57 microM, respectively, while did not inhibit FabI, the enoyl-ACP reductase of either Escherichia coli or Staphylococcus aureus, even at 200 microM. Atromentin and leucomelone are the first inhibitors specific to the enoyl-ACP reductase (FabK) of Streptococcus pneumoniae.

In our screening program for new antifungal agents from microbial secondary metabolites, two new isoflavonol glycosides, with potent antifungal activity, talosins A and B, were isolated from the culture broth of Kitasatospora kifunensis MJM341. Talosins A and B were determined to be genistein 7-alpha-L-6-deoxy-talopyranoside and genistein 4',7-di-alpha-L-6-deoxy-talopyranoside, respectively, by spectroscopic studies. They are the first flavonoid glycosides incorporating 6-deoxy-talose as a sugar component.

Ethanol extract of the aerial portion of Chelidonium majus L. inhibited acetylcholinesterase (AChE) activity without a significant inhibition of butyrylcholinesterase (BuChE). Using mass spectrometry and NMR studies, three active constituents were isolated and identified: 8-hydroxydihydrochelerythrine (1), 8-hydroxydihydrosanguinarine (2), and berberine (3). Compounds 1-3 showed potent inhibitory activity against AChE, with IC50 (microM) values of 0.61-1.85. Compound 1 exhibited competitive and selective inhibition for AChE.

New melanin synthesis inhibitors, melanocins A, B and C, were isolated from the fermentation broth and extract of mycelium of Eupenicillium shearii F80695. The structures of melanocins were established by spectroscopic methods. They are formamide compounds. In particular, melanocin A has an isocyanide group.

The hyperactivity of ionotropic glutamate receptors has been implicated in the development of the neuronal cell death seen in many neurodegenerative processes including ischemic stroke, traumatic brain injury, and epilepsy. Thus neuronal protection against glutamate-induced neurotoxicity is considered as an appropriate therapeutic strategy for preventing and treating neurodegenerative diseases. Whilst searching for blockers of glutamate-induced toxicity in mouse cortical cells, we isolated p-terphenyl curtisians A - D from the mushroom Paxillus curtisii. Curtisians protected cortical neurons from glutamate-induced toxicity in a dose-dependent manner. Among the glutamate receptor subtypes, curtisians were found to block NMDA receptor-mediated but not AMPA/kainate-mediated cell death. In addition, we found that curtisians exhibited potent antioxidative activity against iron-mediated oxidative damage which was generated by H2O2 neurotoxocity and lipid peroxidation, but no activity was detected in the superoxide, DPPH and ABTS radical scavenging systems, and in protection of N18-RE-105 cells subjected to glutamate-induced glutathione depletion. This effect was likely due to the iron chelating properties of curtisians. The iron chelation ability of curtisians was then further investigated on DNA single strand breakage (SSB) induced by the addition of iron and H2O2, and curtisians prevented DNA SSB like the iron chelator desferrioxamine. These results suggest that the neuroprotective action of curtisians is dependent on their ability to chelate iron as well as to block the NMDA receptor, and that in this context curtisians may be useful as neuroprotective agents against neurological disorders which result in neuronal cell death.

Terreulactones A, B, C, and D, new meroterpenoid compounds with potent anti-acetylcholinesterase activity, were determined to be mixed polyketides-terpenoid structures by spectroscopic studies.

In the course of screening for selective inhibitors of acetylcholinesterase from the microbial metabolites, four new meroterpenoid compounds, terreulactones A, B, C and D were isolated from solid state fermentation of Aspergillus terreus Fb000501. They showed potent inhibitory activities against acetylcholinesterase with IC50 values in range of 0.06 to approximately 0.42 microM. In addition, they exhibited more than 500 to approximately 3000 times selectivity for acetylcholinesterase compared with butyrylcholinesterase.

The methanol extracts from the fruiting body of the mushroom Boletus calopus showed free radical-scavenging activity. Bioactivity-guided fractionation of the methanol extracts led to a new hydroxylated calopin named calopin B, along with the known delta-lactones calopin and cyclocalopin A. The structure of the new calopin analogue was elucidated by spectroscopic methods. All compounds showed potent free radical-scavenging activity against superoxide, DPPH, and ABTS radicals with IC (50) values of 1.2 - 5.4 microg/mL.

Phenazostatins A and B, new diphenazine compounds, were isolated from the culture broth of Streptomyces sp. 833 as new neuronal cell protecting substances which also showed free radical scavenging activity. In the cell assay, phenazostatins A and B inhibited glutamate toxicity in N18-RE-105 cells with EC50 values of 0.34 and 0.33 microM, respectively.

Two lipid peroxidation inhibitors, designated as betulinans A (1) and B (2), were isolated from the MeOH extract of Lenzites betulina. The structures of these compounds have been determined to be 2,5-diphenyl-3,6-dimethoxy-p-benzoquinone and 2-phenyl-3-methoxy-[1H-2-benzopyran][4,3-e][p]benzoquinone, respectively, on the basis of various spectral data. Betulinans A and B inhibited lipid peroxidation with IC50 values of 0.46 and 2.88 micrograms/mL, respectively.

In the course of screening for free radical scavengers, rare metabolites, benzastatins A and B having aminobenzamide skeleton and benzastatins C and D having tetrahydroquinoline skeleton, were isolated from the culture broth of streptomyces nitrosporeus 30643. They showed inhibitory activity against lipid peroxidation in rat liver microsomes. In the cell assay, benzastatins C and D inhibited glutamate toxicity in N18-RE-105 cells with EC50 values of 2.0 and 5.4 microM, respectively.