Quantitative and qualitative analysis of sterols/sterolins and hypoxoside contents of three Hypoxis (African potato) spp.

Abstract

The glycoside, hypoxoside, identified and isolated from the corms of the African potato (Hypoxis hemerocallidea) has shown promising anticancer activities. The African potato is used as an African
traditional medicine for its nutritional and medicinal properties. Most research has been carried out on H. hemerocallidea (formerly known as H. rooperi), with very little or nothing on other Hypoxis spp. Thin
layer chromatography (TLC) was used to confirm the presence of sterols/sterolins, whereas a GC method was developed to identify and quantify sterols (especially β-sitosterol) in chloroform extracts of H. hemerocallidea, H. stellipilis and H. sobolifera var. sobolifera. High performance liquid chromatography (HPLC) was used to identify and quantify hypoxoside content in these Hypoxis spp. TLC results showed that H. sobolifera var. sobolifera contained the most sterols and sterolins compared to the other two Hypoxis spp. Gas chromatography (GC) results show that β-sitosterol and campesterol were the two main phytosterols present in the Hypoxis extracts. H. sobolifera var. sobolifera and H. hemerocallidea contained the most β-sitosterol and hypoxoside, respectively. H. sobolifera and H. hemerocallidea contained 74.69 µg of β-sitosterol and 12.27 µg of hypoxoside per 5 mg of chloroform extracts, respectively. These results show a significant difference in the sterol/sterolin and hypoxoside contents between species of the genus Hypoxis, which may influence their degree of biological activities.