Isolation and quantification of β-sitosterol, ergosterol and stigmasterol from Hypoxis rigidula Baker var. rigidula and hypoxis hemerocallidea Fisch., C.A.Mey. & Avé-Lall (Hypoxidaceae)

Abstract

Hypoxis rigidula Baker var. rigidula and Hypoxis hemerocallidea Fisch., C.A.Mey. & Avé-Lall (Hypoxidaceae) are frequently used African medicinal plant that has been used by traditional healers for daily healthcare needs. Phytosterols isolated from Hypoxis spp, have been found to be effective in lowering plasma cholesterol concentration by inhibiting the absorption of cholesterol in the small intestine. Phytosterols serve to stabilize phospholipid bilayers in plant cell membranes just as cholesterol does in animal cell membranes. The aim of this study was to isolate phytosterols from Hypoxis rigidula and evaluate its cholesterol reduction activity. The objectives were to extract phytosterols from Hypoxis using distillation; identify phytosterols using thin layer chromatography (TLC) and quantify phytosterols present in the plant extracts using high performance liquid chromatography (HPLC-UV). TLC gave the following phytosterol standard values: β-sitosterol at Rf 0.63±0, ergosterol at Rf 0.66±0 and stigmasterol at Rf 0.68±0. The chloroform extracts of both H. hemerocallidea and H. rigidula the presence of β-sitosterol, ergosterol and stigmasterol. HPLC analysis gave the following concentrations of phytosterols; 48.4 and 35.2 µg/ml of stigmasterol were found in H. rigidula and H. hemerocallidea respectively and 86.7 and 48.4 µg/ml of ergosterol were found in H. rigidula and H. hemerocallidea respectively. These results show a significant difference in the phytosterol content between the two species of the genus Hypoxis.