A New Carvotacetone Derivative from the Aerial Part of Sphaeranthus africanus

Abstract

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.