Hermannia geniculata is a herb that plays an important role in the treatment of an array of diseases including diabetes, ulcer, and colitis in the South African traditional medicine. The bioactive constituent and medicinal properties in phenols of Hermannia geniculata (PoHG) roots were investigated using high pressure thin layer chromatography (HPTLC). The α-amylase inhibitory potentials of PoHG was determined by reacting different concentration of the plant extract with 1% starch solution containing α-amylase. The inhibitory effect of the extract on α-glucosidase was evaluated by pre-incubating α-glucosidase with varying extract concentrations followed by the addition of ρ -nitrophenylglucopyranoside.. The reactive oxygen and free radical scavenging potentials of the extract were also analyzed. The result showed the presence of phenolic compounds in the extract with retention factor (Rf) values ranging from 0.14 to 095. The extract scavenged DPPH, ABTS+, hydroxyl, and superoxide anion radicals. The extract was able to chelate metallic ions with a lower IC50 value which differs significantly (p≤0.05) from silymarin. Moreover, PoHG extract inhibited the key enzymes (α-glucosidase and α-amylase) involved in carbohydrate catabolism with IC50 values of 1.76 ±0.14 and 7.52 ±0.23 mg/mL respectively while IC50 value reported for acarbose were 7.62 ±0.12 and 4.38 ±0.25 mg/mL for glucosidase and α-amylase, respectively. The α-glucosidase exhibited non-competitive inhibition by PoHG extract while α-amylase showed uncompetitive inhibition. This study confirmed the presence of phenol in PoHG extract and also showed an appreciable antioxidant and antidiabetic activities in vitro. Therefore, PoHG extract may be of nutraceutical importance.
