Bioactive-Guided Phytochemical Investigations, In Vitro and In Silico Alpha-Glucosidase Inhibition of Two Vietnamese Medicinal Plants Dicranopteris linearis and Psychotria adenophylla.

Little is known about the chemical and biological profiles of Dicranopteris linearis and Psychotria adenophylla. No previous studies have investigated alpha-glucosidase inhibition using extracts from D. linearis and P. adenophylla. In this paper, bioactive-guided isolation procedures were applied to the plants D. linearis and P. adenophylla based on alpha-glucosidase inhibition. From the most active fractions, 20 compounds (DL1-DL13 and PA1-PA7) were isolated. The chemical structures were elucidated using spectroscopic data and compared with those available in the literature. These compounds were evaluated for alpha-glucosidase inhibition, while a molecular docking study was performed to elucidate the mechanisms involved. Consequently, D. linearis and P. adenophylla might serve as a good potential for developing new antidiabetic preparations.

A New Carvotacetone Derivative from the Aerial Part of Sphaeranthus africanus.

Sphaeranthus africanus L. is native in Vietnam. Little is known about α-glucosidase inhibition of Sphaeranthus africanus and its isolated compounds. A bioactive-guided isolation was applied to the Vietnamese Sphaeranthus africanus to find α-glucosidase inhibitory components. Eight compounds were detected and structurally elucidated. They are 3-angeloyloxy-5-[2'',3''-epoxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[3''-chloro-2''-hydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''R,3''R-dihydroxy-2''-methyl-butanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''S,3''R-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''S,3''S-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 5-angeloyloxy-7-hydroxy-3-tigloyloxycarvotacetone, 3-O-methylquercetin, and chrysosplenol D. Their chemical structures were elucidated by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy as well as comparisons in literature. 3-Angeloyloxy-5-[2''S,3''S-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone is a new compound. Isolated compounds were evaluated for the α-glucosidase inhibition. Isolated compounds showed moderate activity with IC50 values ranging from 128.9-274.3 µM while others are weak. A molecular docking study was conducted, indicating that isolated compounds are potent α-glucosidase inhibitory compounds.

Tecomastane, a new megastigmane from the flowers of Tecoma stans.

Tecoma stans is a tropical plant that is widely used in folk medicine. Little is known about the chemical constituents of flowers of this plant. From flowers of the native plant in Vietnam, 12 compounds were isolated and elucidated, including one new compound tecomastane (1) and eleven known compounds, (3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmane-9-one (2), bosciallin (3), chakyunglupulin B (4), (2S,6R)-2,6-dimethyloctane-1,8-diol (5), cleroindicin F (6), rengyoxide (7), 3,4-dihydroxybenzoic acid (8), methyl 3,4-dihydrobenzoate (9), 3,5-dihydroxybenzoic acid (10), luteolin (11), and indole-3-carboxylic acid (12). Compound 5 was a new natural product. The chemical structures of isolated compounds were identified by interpretation of their spectroscopic data (1D, 2D NMR, and HRESIMS) and by comparison with the literature. Compounds 1-7 and 10-12 were evaluated for alpha-glucosidase inhibition and antimicrobial activity against antibiotic-resistant, pathogenic bacteria Enterococcus faecium, Staphylococcus aureus, and Acinetobacter baumannii.

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).

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].

Ricicomin A, a new alkaloid from the leaves of Ricinus communis Linn.

From the leaves of Ricinus communis Linn., one new alkaloid, named ricicomin A (1) together with three known ones, ricinine (2), N-demethylricinine (3) and 4-[2-formyl-5-(methoxymethyl)-1H-pyrrol-1-yl]butanoic acid (4) were justified by repeated chromatographic methods. Their structures were determined by comprehensive IR, HR-ESI-MS and NMR analyses. Compound 4 was identified for the first time from the genus Ricinus. DFT-NMR chemical shift calculations and subsequent DP4+ probability methods were applied to confirm the chemical structure of 1. Compounds 1-3 did not display cytotoxic effect against three human cancer cell lines (MCF-7, HepG2 and HeLa) using SRB assay.

Stercufoetin A, new oleanane-type triterpenoid from the leaves of Sterculia foetida L.

From the leaves of Sterculia foetida L., one new oleanane-type triterpenoid, named stercufoetin A (1) together with four known ones, vergatic acid (2), ß-amyrin (3), oleanolic acid (4) and maslinic acid (5) were purified by diversely chromatographic methods. Their structures were proposed by HR-APCI-MS and NMR experiments. Compounds (2-5) were notified for the first time from this species. Compound 1 showed weak cytotoxic effect against three human cancer cell lines (MCF-7, HepG2 and HeLa) using SRB assay.

Salazinic Acid-Derived Depsidones and Diphenylethers with α-Glucosidase Inhibitory Activity from the Lichen Parmotrema dilatatum.

Three new depsidones, parmosidones F - G (1 - 2), and 8'-O-methylsalazinic acid (3), and 3 new diphenylethers, parmetherines A - C (4 - 6), together with 2 known congeners were isolated from the whole thalli of Parmotrema dilatatum, a foliose chlorolichen. Their structures were unambiguously determined by extensive spectroscopic analyses and comparison with literature data. The isolated polyphenolics were assayed for their α-glucosidase inhibitory activities. Newly reported benzylated depsidones 1: and 2: in particular inhibited α-glucosidase with IC50 values of 2.2 and 4.3 µM, respectively, and are thus more potent than the positive control, acarbose.

Markhasphingolipid A, new phytosphingolipid from the leaves of Markhamia stipulata var. canaense V.S. Dang.

From the leaves of Markhamia stipulata var. canaense V.S. Dang, one new phytosphingolipid, named markhasphingolipid A (6) together with five known compounds, 4',7-O-dimethylapigenin (1), narigenin (2), tectoquinone (3), mollic acid (4), 1-hexadecanoyl-sn-glycerol (5) were classified by various chromatographic methods. Their structures were designated by IR, UV, HR-ESI-MS, HR-ESI-MS/MS and NMR experiments. All compounds were recognized for the first time from this species. The cytotoxicity of all n-hexane fractions and isolated compounds (5 & 6) against three human cancer cell lines (HeLa, HepG2, and MCF-7) were evaluated by SRB assay. All n-hexane fractions expressed cytotoxic effect on three tested cancer cell lines (at the concentration of 100 µg/mL, percent of cytotoxicity ranged from 55.81% to 95.83%) as well as compound 5 (IC50 ranged from 48.51 to 63.30 µM) whereas fraction H.I and compound 6 did not show activity.[Formula: see text].

Markhacanasin C, cycloartane triterpenoid from the leaves of Markhamia stipulata var. canaense V.S. Dang.

One new cycloartane triterpenoid, named markhacanasin C (1), together with three known triterpenoids, oleanolic acid (2), ursolic acid (3) and 6ß,19α-dihydroxyursolic acid (4) were isolated by various chromatographic methods from the most cytotoxic fraction of the ethyl acetate extract of Markhamia stipulata var. canaense V.S. Dang leaves. Among them, 4 was reported for the first time from the genus Markhamia, while 2 and 3 were found for the first time from this species. Their structures were elucidated by IR, UV, HR-ESI-MS and NMR experiments. The cytotoxicity of isolated compounds (3 and 4) against three human cancer cell lines (HeLa, HepG2, and MCF-7) were evaluated. At the concentration of 100 µg/mL, 3 exhibited significant cytotoxic activity (86.36 ± 3.69%).