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.