Unravelling the Potentials of Managing Metabolic Diabetes and Related Oxidative Stresses with Extracts from Five South African Hypoxis Species

Abstract

Hypoxis species (Hypoxidaceae) comprises twenty-nine species, but the research spotlight is on Hypoxis hemerocalldea (H. hemerocallidea). This study focused on the determination of phytochemical variations, total phenolic content, and antioxidant and antidiabetic potentials of five Hypoxis species from South Africa with the aim of averting over-harvesting and extinction of H. hemerocallidea. Standard protocols were used to determine six classes of phytochemicals, their variations, and antidiabetic and antioxidant potentials. Results obtained included variable phytochemicals (tannins, terpenoids, saponins, and deoxy sugar) content. All five Hypoxis species tested positive for antioxidants with 0.2 mM 1,1-diphenyl-2-picrylhydrazyl solution. In terms of quantitative antioxidant activity, Hypoxis obtusa displayed the best inhibition of 96.79% (IC50 = 0.15 mg/mL) for 1,1-diphenyl-2-picrylhydrazyl and 96.93% (IC50 = 0.04 mg/mL) for hydrogen peroxide, while Hypoxis colchicifolia attained the lowest inhibition of 81.43% (IC50 = 0.23 mg/mL) for 1,1-diphenyl-2-picrylhydrazyl and 81.25% (IC50 = 0.05 mg/mL) for hydrogen peroxide. Furthermore, Hypoxis obtusa and Hypoxis hemerocallidea afforded the best antioxidant activity of 65.64% (IC50 = 0.32 mg/mL) and 65.23% (IC50 0.81 mg/mL) for the ferric reducing antioxidant power assay. The antidiabetic potentials were similar with Hypoxis hemerocallidea and Hypoxis obtusa equally inhibiting the two enzymes, with IC50 of 0.21 mg/mL, 0.24 mg/mL, just like the standard acarbose with IC50 of 0.20 mg/mL. The other three Hypoxis extracts exhibited comparative antidiabetic inhibitory effects with IC50 ranging from 0.34 to 0.55 mg/mL.