Stigmastane-type steroid saponins from the leaves of Vernonia amygdalina and their α-glucosidase and xanthine oxidase inhibitory activities

Two new vernonioside K (1) and vernonioside L (2) and four known Δ7,9(11) stigmastane-type steroidal saponins-vernonioside B2 (3), vernoniacum B (4), vernonioside B1 (5), and vernoamyoside A (6)-were isolated from the leaves of Vernonia amygdalina. Their structures were determined by comprehensive spectroscopic analysis with one-dimensional nuclear magnetic resonance, two-dimensional nuclear magnetic resonance, and high-resolution mass spectrometry. All isolated compounds (1-6) were evaluated to determine their inhibitory effects on α-glucosidase and xanthine oxidase. Among them, two new compounds 1 and 2 showed significant inhibition of α-glucosidase with IC50 values of 78.56 ± 7.28 and 14.74 ± 1.57 (μM), respectively, comparable with acarbose as a positive control (127.53 ± 1.73 μM); none of these compounds inhibited xanthine oxidase activity. Compounds 1 and 2 are promising candidates for the development of antidiabetic agents from natural sources.

In vitro and in silico cytotoxic activities of triterpenoids from the leaves of Aralia dasyphylla Miq. and the assessment of their ADMET properties

From the methanol extract of the leaves of Aralia dasyphylla Miq. (Araliaceae), ten triterpenoids including five ursane-type triterpenoids, ursolic acid (1), 3-O-α-l-arabinopyranosyl ursolic acid (2), ursolic acid 28-O-β-D-glucopyranosyl ester (3), 3-O-[β-D-glucopyranosyl (l→3)]-α-L-arabinopyranosyl ursolic acid (4), and matesaponin 1 (5), and five oleanane-type triterpenoids, elatoside E (6), elatoside F (7), 3-O-[β-D-glucopyranosyl (l→3)]-α-L-arabinopyranosyl oleanolic acid (8), 3-O-α-L-arabinopyranosyl oleanolic acid (9) and oleanolic acid 28-O-β-D-glucopyranosyl ester (10) were isolated. Their structures were elucidated based on 1D-, 2D-NMR and ESI-MS spectra as well as by comparison with those reported in the literature. All isolated compounds were evaluated in vitro for their cytotoxic activities against three human cancer cell lines (HepG2, LU-1 and RD) and in silico by molecular docking studies on human glucose transporter 1 (hGLUT1) protein. The triterpenoids 2, 4, 6, 8 and 9 exhibited good growth inhibition of HepG2 and LU-1 cancer cell lines with IC50 values in the range 1.76 - 7.21 (μM). The oleanane type triterpenoid 8 was the highest cytotoxic compound to inhibit all the tested cancer cell lines with IC50 values of 2.73 ± 0.12, 1.76 ± 0.11, 2.63 ± 0.10 μM, respectively. The in silico molecular docking study results showed that compounds 4 and 6 had the highest binding affinity. Compounds 1-10 were evaluated for their in silico ADMET of absorption, distribution, metabolism, excretion and oral toxicity parameters. Compounds 6, 8, 9 and 10 from A. dasyphylla are potential hGLUT1 inhibitors and worth of further investigation for the prevention or treatment of diabetes and cancer.Communicated by Ramaswamy H. Sarma.