Inhibitory effects of different varieties of sweet potato (Ipomoea batatas L.) tubers extracts on lipoxygenase activity

Background: Sweet potatoes (Ipomoea batatas L.) with purple, orange and white varieties can be differentiated by their skin and flesh tubers' colors. Research on anti-inflammatory activity of this plant is still limited although has been used traditionally. Objective: This study aimed to determine IC₅₀ value of sweet potato tubers extracts in inhibiting lipoxygenase activity. Methods: Dried tubers of sweet potato were macerated with ethanol 70%. Each extracts were tested for soybean lipoxygenase inhibitory activity, phytochemical screening and total flavonoid contents. IC₅₀ value and total flavonoid contents obtained from each extracts were analyzed statistically. Results: IC₅₀ value of purple, orange and white sweet potato tubers extracts are 46.09, 52.12 and 63.69 μg/mL respectively. Each extracts contain alkaloids, flavonoids, saponins, tannins and glycosides. Total flavonoid contents in purple, orange and white sweet potato extracts are 8.45±0.41; 7.57±0.03; and 6.12±0.14 mgQE/g extract respectively. Conclusion: Total flavonoid contents and IC₅₀ values of each extracts are strongly correlated and inversely proportional with significance value of 0.026 and correlation value of -0.999 which indicate that the higher total flavonoid contents, the stronger inhibitory activity.