Antioxidant, Hypoglycemic Activities and Inhibitory Effect on Tyrosinase of Ethanol Extracts of Different Parts from Psidium guajava L.

Objective: The antioxidant, hypoglycemic and tyrosinase inhibitory activities of ethanol extracts of different parts (root, stem, leave and fruit) from Psidium guajava L. were compared. Methods: The free radical scavenging were determined by DPPH and ABTS method. The hypoglycemic activities were determined by pNPG and DNS method. The inhibition of tyrosinase activity was determined by L-DOPA method. Results: The ethanol extracts of different parts from Psidium guajava L. had certain antioxidant, hypoglycemic activities and inhibitory effect on tyrosinase, and there were dose effect relationship. The ethanol extracts of the root from Psidium guajava L. had the strongest activity, and its free radical scavenging of ABTS⁺ and DPPH was close to V_C, its IC₅₀ values of the scavenging ability of ABTS⁺ and DPPH free radicals were (8.45±0.12), (0.09±0.002) mg/mL, and its inhibitory strength on yeast α-glucosidase and α-amylase was higher than that of positive control acarbose. And its IC₅₀ values of the inhibitory activity on α-amylase and yeast α-glucosidase were: (0.10±0.02), (8.74±0.25) μg/mL, and the inhibitory activity of tyrosinase was weaker than V_C. Conclusion: The ethanol extract of the root from Psidium guajava L. had the highest antioxidant, hypoglycemic activities and inhibitory effect on tyrosinase, which suggested that the root from Psidium guajava L. is a potential inhibitors resource of antioxidant, α-glucosidase, α-amylase and tyrosinase.