Phytochemical Screening, Free Radical Mitigation and Antidiabetic Potentials of Pentanisia prunelloides (Klotzsch ex Eckl. & Zeyh.) Walp. Root Extracts

Diabetes mellitus is attributed as one of the major health problems globally. This study evaluated the antioxidative and antidiabetic potentials of P. prunelloides in an in-vitro model and also screened for the presence of phytochemicals in the extracts. The antioxidant activity of the extracts (water, ethanol, aqueous-ethanol and hexane) was determined by superoxide anion, hydroxyl, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assays and iron chelation method while the antidiabetic potential was assessed by determining the inhibitory effects of the extracts on the activities of α-amylase, α-glucosidase, maltase and sucrase enzymes. The hexane extract displayed significantly higher (p < 0.05) inhibition of α-amylase (0.48 μg/mL) and α-glucosidase (18.08 μg/mL) respectively. Additionally, water extract demonstrated strong inhibition of sucrase (3.85 μg/mL), and aqueous-ethanol extract (26.03 μg/mL) on maltase activity when compared with other extracts and control. The Lineweaver Burke plot revealed the non-competitive inhibition of α-amylase and α- glucosidase by the ethanol extract. While hexane extract demonstrated significant (p < 0.05) scavenging activities against superoxide anion (0.33 μg/mL) and hydroxyl radical (0.51 μg/mL), water (75.42 μg/mL) and aqueous-ethanol (4.24 μg/mL) extracts exhibited the strongest DPPH activity and iron chelation effect respectively. The phytochemical analysis of the extract revealed the presence of tannins, terpenoids, alkaloids, saponins, flavonoids and cardiac glycosides while quantification of phytochemicals revealed total flavonoids with 15.40 mg quercetin equivalent (QE)/g from hexane extract, highest tannin content with 45.60 mg gallic acid equivalent (GAE)/g (aqueous-ethanol extract) and total phenol from water and aqueous- extracts with 0.07 mg GAE/g while alkaloids and saponins contents were found to be low in the roots of P. prunelloides, at 0.6 and 13.9% respectively. It can therefore be concluded that P. prunelloides extracts possessed antioxidant and antidiabetic activities in vitro and could thus be suggested that its mechanism of antidiabetic action is through the inhibition of diabetes-related enzymes.