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

Abstract

Two new vernonioside K (1) and vernonioside L (2) and four known Δ^7,9(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.

Graphical Abstract

Keywords:

• Vernonia amygdalina
• Δ^7,9(11)stigmastane-type steroidal saponin
• α-glucosidase
• xanthine oxidase

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This research was supported by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.01-2020.11. In addition, Pham Van Cong was funded by Vingroup Joint Stock Company and supported by the Domestic Master/Ph.D. Scholarship Programme of Vingroup Innovation Foundation (VINIF), Vingroup Big Data Institute (VINBIGDATA), code VINIF.2022.TS017.