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Biotransformation of betulonic acid (1) by Rhizopus arrhizus CGMCC 3.868 resulted in the production of 16 new (3, 5, 6, and 9-21) and five known compounds. Structures of the new compounds were established by analysis of spectroscopic data. Hydroxylation, acetylation, oxygenation, glycosylation, and addition reactions involved the C-20-C-29 double bond. Antineuroinflammatory activities of the obtained compounds in NO production were tested in lipopolysaccharides-induced BV-2 cells. Compared with the substrate betulonic acid, biotransformation products 3, 8, 9, 14, and 21 exhibited an improved inhibitory effect, with IC50 values of 10.26, 11.09, 5.38, 1.55, and 4.69 μM, lower than that of the positive control, NG-monomethyl-l-arginine.

The members of the arylamine N-acetyltransferase (NAT) family of enzymes are important for their many roles in xenobiotic detoxification in bacteria and humans. However, very little is known about their roles outside of detoxification or their specificities for acyl donors larger than acetyl-CoA. Herein, we report the detailed study of PtmC, an unusual NAT homologue encoded in the biosynthetic gene cluster for thioplatensimycin, thioplatencin, and a newly reported scaffold, thioplatensilin, thioacid-containing diterpenoids and highly potent inhibitors of bacterial and mammalian fatty acid synthases. As the final enzyme of the pathway, PtmC is responsible for the selection of a thioacid arylamine over its cognate carboxylic acid and coupling to at least three large, 17-carbon ketolide-CoA substrates. Therefore, this study uses a combined approach of enzymology and molecular modeling to reveal how PtmC has evolved from the canonical NAT scaffold into a key part of a natural combinatorial biosynthetic pathway. Additionally, genome mining has revealed the presence of other related NATs located within natural product biosynthetic gene clusters. Thus, findings from this study are expected to expand our knowledge of how enzymes evolve for expanded substrate diversity and enable additional predictions about the activities of NATs involved in natural product biosynthesis and xenobiotic detoxification.

A new resin glycoside named evolvulin III (1) was isolated from the whole plants of Evolvulus alsinoides. Compound 1 was identified as a pentasaccharide macrolactone with a distinctive 3S,11R,14R-trihydroxyhexadecanoic acid acting as the aglycone. Interestingly, evolvulin III (1) is interconvertible with a known resin glycoside, namely, evolvulin II (2), by intramolecular transesterification. The structure of compound 1 was determined by spectroscopic data and the chemical analysis of the equilibrium mixture of 1 and 2.

Alkaline hydrolysis of the resin glycoside fraction of the whole plants of Convolvulus arvensis gave two new glycosidic acids, named arvensic acids K and L (1 and 2). Their structures were characterized on the basis of spectroscopic data as well as chemical evidence. They possessed a same pentasaccharide chain, composed of one D-fucose, three D-glucose and one L-rhamnose units. The aglycone of compound 1 was identified to be rarely existing 11S-hydroxyheptadecanoic acid, while compound 2 possessed 11S-hydroxyhexadecanoic acid as the aglycone. Their cytotoxic and anti-migration activities were also evaluated.

Evolvulins I and II (1 and 2), representing a new class of resin glycosides with an unprecedented trihydroxy aglycone unit, 3S,11R,14R-trihydroxyhexadecanoic acid (4), were isolated from the whole plants of Evolvulus alsinoides. Their structures were thoroughly characterized by extensive spectroscopic analyses as well as chemical evidence. Compound 1 exhibited the most potent cytotoxic activity against MCF-7 cells, with an IC50 value of 3.12 μM.

Six new glycosidic acids, arvensic acids E-J (1-6), were obtained from a glycosidic acid fraction afforded by alkaline hydrolysis of the crude resin glycosides from Convolvulus arvensis whole plants. Their structures were established from the spectroscopic data obtained and by chemical evidence. They were defined as heptasaccharides or hexasaccharides, comprising d-fucose, d-glucose, and l-rhamnose units. Compounds 1, 3, and 5 were assigned the 11 S-hydroxyheptadecanoic acid as the aglycone, while compounds 2, 4, and 6 were found to possess 11 S-hydroxyhexadecanoic acid as the aglycone. Compounds 1, 3, and 5 are the first representatives of resin glycosides with 11 S-hydroxyheptadecanoic acid as the aglycone.

Two new glycosidic acids, evolvulic acids B and C (1 and 2), along with a known one, evolvulic acid A (3), were isolated from the glycosidic acid fraction afforded by alkaline hydrolysis of crude resin glycosides from Evolvulus alsinoides whole plants. Their structures were characterized by the spectroscopic data and chemical evidences. Compounds 1 and 2 are both defined as tetrasaccharides, composed of D-fucose, D-glucose, L-rhamnose or D-galactose units. Their aglycones are identified to be a distinctive 3S,11R,14R-trihydroxyhexadecanoic acid, which is only discovered from E. alsinoides up to now. The cytotoxic and anti-migration activities of compounds 1–3 were also tested.

In this study, a resin glycoside fraction with cytotoxic activity was isolated from the alcoholic extract of C. arvensis whole plants. To describe the chemical feature of the resin glycosides, the fraction was alkaline hydrolyzed and four novel glycosidic acids, named arvensic acids A-D (1-4), were isolated. Their structures were thoroughly elucidated on the basis of spectroscopic data and chemical evidences. They all possess a same heptasacharride core, consisting of one D-fucose, two L-rhamnose and four d-glucose units. The difference among these glycosidic acids was placed on the aglycone, which is 12S-hydroxypentadecanoic acid for 1, 12S-hydroxyhexadecanoic acid for 2, 3S,12S-dihydroxypentadecanoic acid for 3, and 3S,12S- dihydroxyhexadecanoic acid for 4. These aglycones are rarely found in the structures of resin glycosides and are firstly identified in the genus Convolvulus.

Biotransformation of lupane-type triterpenoid betulin was carried out with Mucor subtilissimus CGMCC 3.2456. Yielded nine previously undescribed hydroxylated compounds. M. subtilissimus biotransformation provided C-7, C-11, C-15 and C-24 hydroxylated compounds along with C-7 oxidized and C-28 acetylated derivatives. The structures of the metabolites were established based on extensive NMR and HR-ESI-MS data analyses. Furthermore, we found that most of the metabolites exhibited pronounced inhibitory activities on lipopolysaccharides-induced NO production in RAW264.7 cells.

Water spinach (I. aquatica) is one of the common green leafy vegetables used in Asia. In a continuing chemical investigation on the cytotoxic resin glycosides from water spinach, eight new resin glycosides, Aquaterins XII–XIX (1–8), were isolated, among which 1, 2 and 4 exhibited potent cytotoxic activities. To further characterise the anticancer potential of the resin glycosides from water spinach, Aquaterin II obtained previously was investigated on HepG2 cells. The results showed that Aquaterin II induced G0/G1 arrest regulated by related proteins CDK4/6, cyclin D/E and p21, and caused mitochondria-mediated apoptosis featured by MMP decrease, ROS accumulation, caspase cascade activation and Bax/Bcl-2 alteration. Additionally, the suppression on PI3K/Akt signalling pathway was observed, suggesting that it participated in the Aquaterin II-induced cell growth inhibition. Our results are the first to demonstrate the antiproliferative mechanism of resin glycosides. This investigation also advanced the potential application of water spinach as a functional food.

Two new resin glycosides, cuses 3 (1) and 4 (2), were initially obtained from the seeds of Cuscuta chinensis. Both of them contained a reducing glucose unit, and thus existed as a pair of isomers. In order to solve the existing problem of tautomerism, the remanent resin glycoside fraction was converted into aminoalditol derivatives with p-anisidine, and then another eight new resin glycosides cuses 5–12 (3–10) were further isolated. Cuses 7–12 (6–10) were considered to be generated via glycosidation of two acylated oligosaccharides, and thus characterized as ether-type resin glycoside dimers. Their structures including absolute stereochemistry were elucidated by a combination of spectroscopic and chemical methods. Compounds 3–10 exhibited cytotoxic activity toward MCF-7, SMMC-7721, and MG-63 cell lines with IC50 values ranging from 8.72 to 59.35 μg/mL.

Nine biflavonoids (1–9) were isolated from ethanolic extract of Selaginella uncinata (Desv.) Spring. Their structures were determined by spectra analysis. Compounds 1–9 were classified into four types according to the connection styles of the two flavonoid parts. Among them, 1 was elucidated as a new compound, while 4 was one with a new configuration. All isolates exhibited inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) in an enzyme assay with IC50 values ranging from 4.6 to 16.1 μM, and the relationship between the structures and activities was discussed. Docking simulations of these compounds demonstrated they had tight binding capacities towards the allosteric site of PTP1B. Additionally, the glucose uptake activities of 1–9 were evaluated in insulin-resistant HepG2 cells, while the effect of 1 on the activation of IRS-1/PI3K/Akt pathway was revealed by Western Blot analysis.

Oxidative stress plays a critical role in the pathogenesis of diabetic vascular complications. Trans-δ-viniferin (TVN), a polyphenolic compound, has recently attracted much attention as an antioxidant exhibiting a hypoglycemic potential. In the present study, we aimed at investigating the protective effect of TVN against high glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) and the potential mechanism involved. We found that TVN attenuated reactive oxygen species (ROS) production, increased catalase (CAT) activity and decreased malondialdehyde (MDA) levels to ameliorate cell survival induced by 35 mM glucose. Meanwhile, it inhibited high glucose-induced apoptosis by maintaining Ca(2+) and preserving mitochondrial membrane potential (MMP) levels. The immunoblot analysis indicated that TVN efficiently regulated the cleavage of caspase family, p53, Bax and Bcl-2, all mediated by SIRT1. Furthermore, the increased level of SIRT1 induced by TVN was inhibited by nicotinamide and siRNA-medicated SIRT1 silencing (si-SIRT1), thereby confirming the significant role of SIRT1 in these events. In conclusion, our results indicated that TVN efficiently reduced oxidative stress and maintained mitochondrial function related with activating SIRT1 in high glucose-treated HUVECs. It suggested that TVN is pharmacologically promising for treating diabetic cardiovascular complications.

Eleven new resin glycosides, aquaterins I-XI (1-11), were isolated from the whole plants of Ipomoea aquatica. The structures of 1-11 were elucidated by a combination of spectroscopic and chemical methods. They were found to be partially acylated tetra- or pentasaccharides derived from simonic acid B and operculinic acids A and C. The site of the aglycone macrolactonization was placed at C-2 or C-3 of the second saccharide moiety, while the two acylating residues could be located at C-2 (or C-3) of the second rhamnose unit and at C-4 (or C-3) on the third rhamnose moiety. All compounds were evaluated for cytotoxicity against a small panel of human cancer cell lines. Compound 4 exhibited the most potent activity against HepG2 cells with an IC50 value of 2.4 μM. Cell cycle analysis revealed 4 to inhibit the proliferation of HepG2 cells via G0/G1 arrest and apoptosis induction. In addition, compounds 1-4, 7, 9, and 10 were found to elevate Ca(2+) in HepG2 cells, which might be involved in the regulation of the cytotoxic activities observed.