IN VITRO AND IN SILICO ANTIOXIDANT ACTIVITY OF PURIFIED FRACTIONS FROM PURPLE SWEET POTATO ETHANOLIC EXTRACT

ABSTRACT Objective: Purple sweet potato (Ipomoea batatas L.) contains antioxidant compounds like anthocyanins (cyanidin and peonidin). Therefore, the current study was conducted to obtain anthocyanins fractions from purple sweet potato with evaluation of its antioxidant activity following ferrous ion chelating (FIC) method and comparing its activity with Na2EDTA. Furthermore, the oxidative molecular mechanism of purified fractions was investigated by in silico molecular docking to superoxide dismutase (SOD) and glutathione peroxidase (GPX). Methods: Evaluating antioxidant activity by using FIC method performed by observing the absorbance of a mixed solution of (NH4)2 Fe(SO4)2, ferrozine and purified fraction measured using a UV-Vis spectrophotometer. Linear regression was used to calculate the IC50 value. Molecular docking was performed using 4.2 Autodock program. Data obtained in the form of docking score. Lower binding energy value show more stable bond between the active compound and its target protein, SOD and GPX. Results: Anthocyanin purified fraction has strong antioxidant capabilities with IC50 value of 74.44 ± 1.29 ?g/mL, but was significantly lower with Na2EDTA (p <0.05). The other mechanism is its ability to induce the target protein such as SOD and GPX intracellular defense body to capture free radicals. But it still lower affinity than native ligand to the target protein GPX is -4.28 kcal / mol while the native ligand with GPX of -7.12 kcal / mol. While the bond between peonidin with SOD is greater affinity (-4.21 kcal / mol) than the native ligand (-0.86 kcal / mol). Conclusion: Anthocyanin purified fraction of purple sweet potato has a very potent antioxidant activity through two mechanisms as well as the metal chelating by using in vitro assay and free radical scavenger by inducing SOD. Keywords: Antioxidant, anthocyanin purified fraction, FIC, SOD, GPX