Carica papaya seeds have been reported in folklore medicine as a remedy used in treating diabetes mellitus without a proper documented possible mode of action. This study aimed at evaluating antioxidant and anti-diabetic activities of Carica papaya seed extracts in vitro. The air-dried ripe seeds were coarsely powdered and extracted via the soxhlet method to obtain their crude extracts. The crude extracts were then furthermore fractionated using hexane, ethyl acetate, methanol, and aqueous. The fractions obtained were assessed for α-glucosidase inhibitory activity. Based on results obtained, the ethyl acetate fractions C and D were further purified to obtain two subfractions each designated as subfraction K, L, M and N. These were then evaluated for in vitro antioxidant and anti-diabetic activities. The mode of inhibition was determined using the Lineweaver Burk plot. Gas chromatography-mass spectrometry analysis of subfraction K was also carried out. The results revealed that ethyl acetate fraction C and D showed maximum inhibitory activity. It was further purified in different solvents and the maximum activity was shown by the ethyl acetate subfraction K (IC50 values). The competitive mechanism of action of Carica papaya seed subfraction K could be due to its inhibitory effects on both α-amylase and α-glucosidase. This may be due to the presence of bioactive compounds detected in the subfraction. Our findings showed strong antioxidant activity and anti-diabetic effect through a competitive inhibition on the activities of α-amylase and α-glucosidase, thereby interfering with the conversion of carbohydrates into glucose. This study has further validated the folklore medicinal use of the Carica papaya seed in the management of diabetes traditionally and uses for other related illnesses.
Keywords: Carica papaya seed; Diabetes mellitus; postprandial hyperglycemia; antioxidant; inhibitors.