The isolation and characterization of lupeol-3-acetate from the hyperglycaemia-lowering fraction of the stem bark of <i>Crystophyllum albidum</i> G. Don (Sapotaceae)

Abstract

This study investigated the hyperglycaemia-lowering activity of the extract and partitioned fractions of the stem bark of Chrysophyllum albidum, and isolation of a bio-active compound from the most active fraction. Powdered stem bark of the plant was extracted with methanol and the extract (A) was tested in glucose-induced hyperglycaemic rats at 100, 200 and 400 mg/kg. The extract was partitioned to obtain its n-hexane (B₁), dichloromethane (B₂), ethyl acetate (B₃) and mother liquor (B₄) fractions that were tested for blood glucose lowering activity using glucose-induced hyperglycaemic model at the most active dose of the extract. The results were subjected to ANOVA followed by Student–Newman-Keuls post hoc tests and p< 0.05 was considered significant. The extract (A) gave dose dependent activity with 400 mg/kg giving the highest percentage blood glucose level reduction of 13% at 4 h that was comparable to the standard, glibenclamide at 5 mg/kg. Fractions B₁ and B₂ gave a time-dependent activity up to the fourth hour similar to glibenclamide, while B₃ and B₄ were devoid of hyperglycaemia-lowering activity. Furthermore, B₁ gave 3, 18, 19 and 29% blood glucose levels reduction at 0.5, 1, 2 and 4 h respectively while B₂ gave 12, 28, 33 and 41% blood glucose levels reduction at 0.5, 1, 2 and 4 h respectively. The activity of B₂ was significantly (p<0.05) more active than glibenclamide at all-time point. The dichloromethane fraction (B₂), most active, was subjected to column and preparative thin layer chromatography and the fraction afforded lupeol-3-acetate. The structure was validated by using Bruker Ascend 400 NMR instrument and the NMR data was compared with literature. The compound was one of the compounds responsible for the biological activity observed as reported by Lakshmi and his co-workers, 2014.

Keywords: Chrystophyllum albidum, Anti-hyperglycaemia, Stem bark, Chromatography, lupeol-3-acetate