A new β-caryophyllene type sesquiterpenoid pentoside with nine known compounds from the aerial parts of Biebersteinia heterostemon as a α-glucosidase inhibitor in vitro

Abstract

To elucidate the chemical basis of the hypoglycemic activity of Biebersteinia heterostemon Maxim, a Tibetan folk medicinal herb, a new β-caryophyllene type sesquiterpenoid pentoside (1) and nine known compounds (2–10) were isolated from its aerial part, and their structures were identified by the use of UV, NMR and HR-MS analyses. Significantly, the compound 1 was isolated from this plant for the first time in the form of a pentaglycoside. The results of α-glucosidase inhibitory activity assays indicated that the compound 1, ethyl acetate fraction, compound 2 and remaining aqueous fraction exhibited weak inhibitory activity, with IC₅₀ values of 2.46, 3.59, 4.87 and 5.03 mg/mL, respectively, all of which were weaker inhibitory activity than that of the positive control, acarbose (IC₅₀ = 0.78 mg/mL). Among the tested samples, compound 1 displayed the most promising inhibitory activity, with an inhibition rate of 70.90 ± 6.07 % at a concentration of 5.0 mg/mL. In contrast, among the other isolated compounds, especially the flavonoid compounds (5–10), some showed low inhibitory activities, while others showed no inhibitory activity at all.