Induction of Endoplasmic Reticulum Stress by Prodigiosin in Yeast Saccharomyces cerevisiae.

Prodigiosin, a red pigment produced by numerous bacterial species, exerts various antibiotic effects on prokaryotic and eukaryotic organisms. For instance, human carcinoma cell lines appear to suffer from endoplasmic reticulum (ER) stress in the presence of prodigiosin. Here, we demonstrated that prodigiosin also triggers the unfolded-protein response (UPR), which is a cytoprotective response against ER stress, in yeast Saccharomyces cerevisiae. An S. cerevisiae mutant carrying a UPR-deficient mutation was hypersensitive to prodigiosin. Our observations cumulatively indicate that protein folding in the ER is impaired by prodigiosin, illustrating a new mode of action.

A new cucurbitane - type triterpenoid from the bark of Elaeocarpus hygrophilus Kurz.

A new cucurbitacin, 3ß-(ß-D-glucopyranosyloxy)-5ß,6ß:16α,23α-diepoxycucurbit-24-en-11-one or hygrocucurbin A (1), along with two known compounds, including 3ß-(ß-D-glucopyranosyloxy)-16α,23α-epoxycucurbita-5,24-dien-11-one (2) and (+)-lyoniresinol (3), were isolated from the bark of Elaeocarpus hygrophilus. Their chemical structures were elucidated by spectroscopic NMR, HR-IDA- TOF-MS analysis, and by comparison with the spectral data of corresponding compounds in the literature. Two cucurbitacins (1) and (2) were evaluated for their α-glucosidase inhibitory activity and cytotoxic against KB, MCF-7, Hep G2, and A549 cancer cell lines. For the α-glucosidase inhibitory activity, compound 1 showed an equivalent effect (IC50 197.4 ± 4.1 µM) compared to the acarbose, a positive control (IC50 208.5 ± 4.7 µM). And for the cytotoxicity, 2 was inactive while 1 was slightly sensitive against KB cells (IC50 233.3 ± 2.5 µM).

Spermacosides a and B, two new triterpenoid saponins from Spermacoce ocymoides burm.f.

Two new triterpenoid saponins, named spermacosides A-B (1 - 2), together with two known oleanane-type triterpenoid saponins, 3-O-ß-D-xylopyranosyl-(1→3)-ß-D-glucopyranosylbayogenin (3) and 3-O-ß-D-glucopyranosylbayogenin (4), were isolated from the ethyl acetate extract of Spermacoce ocymoides Burm.f. in a phytochemical investigation. Their chemical structures were elucidated by spectroscopic data analysis (1D and 2D NMR, and HR-ESI-MS), as well as comparison with reported data. All these compounds were evaluated for inhibiting nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells. Among them, 1 showed a slight effect with an IC50 value of 108.65 ± 7.91 µM, and compounds 2-4 were inactive.

Identification and α-glucosidase inhibitory activity evaluation of two new coumarins derived from Mansonia gagei J. R. Drumm.

Five coumarins were isolated from the heartwood of Mansonia gagei, which included two newly discovered compounds, namely 11-hydroxypopulene E (1) and mansorin D (2), along with three previously identified compounds. The structures were determined through the utilisation of comprehensive spectroscopic data, ECD calculations, and a thorough comparison with existing literature data. The α-glucosidase inhibitory activities of all isolated compounds were assessed in yeast. Out of the compounds tested, compound 2 exhibited the most significant activity, displaying a percentage inhibition of 34.33% at a concentration of 200 µM.

Two new ent-kaurane-type diterpene diastereomers isolated from Coffea canephora.

Phytochemical investigation of the trunks of Coffea canephora yielded two new ent-kaurane diterpene diastereomers, which have been named coffecanepholide A, ent-3ß,16ß,17-trihydroxykauran-18-al (1) and coffecanepholide B, ent-3ß,16ß,17-trihydroxykauran-19-al (2). Structural elucidation and configurational assignment were deduced from extensive spectroscopic NMR/HRESIMS analysis and by comparison with the spectral data of the literature relevant structures. The isolated compounds were assayed for in vitro inhibitory activities against α-glucosidase. Structure 2 showed the α-glucosidase inhibitory activity with an IC50 value of 294.7 ± 0.9 µM, while compound 1 exhibited inactivity. In addition, the docking results revealed that structure 2 can form more interactions with amino acid residues at the active site of α-glucosidase, which gave a more negative binding energy (-9.56 kcal/mol) compared with 1 (-8.60 kcal/mol). This observation might be responsible for a better activity of 2 against α-glucosidase.

Hedyocoronins A and B: two new oleanane saponins from the aerial parts of Hedyotis coronaria.

Two new oleanane saponins, hedyocoronin A (1) and hedyocoronin B (2), were isolated from the aerial parts of Hedyotis coronaria (Kurz) Craib, Rubiaceae, collected at Da Oai district, Lam Dong province in Vietnam. Their chemical structures were elucidated by HR-MS, 1D and 2D-NMR spectra, along with the comparison with those reported in the literature. Compounds 1 and 2 showed weak cytotoxicity against KB and HeLa-S3 cancer cell lines with IC50 values of more than 54 µM.

Jasminanthoside - a new pregnane-steroid from Jasminanthes tuyetanhiae.

A new pregnane steroid, jasminanthoside (1), together with three known compounds, telosmoside A7 (2), syringaresinol (3), and methyl 6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandropyranoside (4) were isolated from the ethyl acetate extract of Jasminanthes tuyetanhiae roots collected in Vietnam. Their chemical structures were elucidated by NMR and MS spectroscopic data analysis along with the comparison of their data with the published ones in the literature. Although 4 was a known compound, its full NMR data were reported for the first time. All isolated compounds, evaluated for their α-glucosidase inhibition, showed activities stronger than the positive control acarbose. Among them, 1 was the best with the IC50 value of 7.41 ± 0.59 µM.

Cafestol analogues from Coffea canephora: in vitro inhibition and molecular docking to α-glucosidase.

A new cafestol-type diterpenoid, 5ß-hydroxy-2-oxocafestol named coffecanepholide C (1) along with three known diterpenoids including cafestol (2), tricalysiolide A (3) and atractyligenin (4) were identified from the Coffea canephora trunks collected at Lam Dong province, Vietnam. Their structures were elucidated by HRESIMS and NMR spectroscopic analysis (1H, 13C, COSY, HSQC, HMBC, and NOESY NMR) as well as compared with data in the literature. Upon evaluation of the α-glucosidase inhibitory activity, compound 1 (IC50 = 142.0 ± 0.2 µM) and compound 3 (IC50 = 286.2 ± 1.2 µM) exhibited activity against α-glucosidase, while structures 2 and 4 showed no activity. Furthermore, the docking simulations revealed that the carbonyl groups of compounds 1 and 3 formed hydrogen bonds with Lys506 residue at the enzyme pocket, which may induce the α-glucosidase inhibitory activity.

A new oleanane-skeleton triterpene isolated from Coffea canephora.

Extensive fractionation of n-hexane extract from the dried powdered-trunks of Coffea canephora Pierre ex A.Froehner (Rubiaceae) led to the isolation of a new oleanane-skeleton triterpene, coffecanolic acid (1), along with three known analogues sumaresinolic acid (2), oleanolic acid (3), and 3-O-acetyloleanolic acid (4). The chemical structures were elucidated using FT-IR, 1D and 2D NMR and HR-ESI-MS data analysis. The isolated compounds were assayed for in vitro α-glucosidase inhibitory activity by determining their half-maximal inhibitory concentration (IC50, µM). Compounds 1-4 exhibited higher inhibitory activities when compared with acarbose, a positive control. Compound 1 was found to be the most potent molecule against α-glucosidase, with the IC50 = 83.0 ± 1.2 µM, which improved by 2.5-fold over acarbose (IC50 = 209.8 ± 0.3 µM) in this assay.[Formula: see text].

Usneaceratins A and B, two new secondary metabolites from the lichen Usnea ceratina.

Two new compounds, comprising one dibenzofuran, named usneaceratin A (1), and one phenolic acid, named usneaceratin B (2), together with one known dibenzofuran, isousnic acid (3), and two known phenolics, orsellinic acid (4) and methyl orsellinate (5) were clarified from the lichen Usnea ceratina using variously chromatographic methods. Their structures were testified by comprehensive HR-ESI-MS, and NMR spectroscopic analysis, and comparison with published data. Their α-glucosidase inhibitory activity of all compounds was measured. Usneaceratin B (2) possessed better inhibition against α-glucosidase enzyme (IC50 value of 41.8 µM) than the standard drug acarbose (IC50 value of 214.50 µM).