Antioxidant activity of methanol extracts and the isolation of new compounds from senggugu’s root bark (Clerodendrum serratum L. moon)

Senggugu is reported to contain potent antioxidant compounds. This study aims to determine the antioxidant activity, to isolate and to characterize the structure of antioxidant compounds of methanolic extract of senggugu’s root bark. The ground dried root bark was macerated gradually with n-hexane, ethyl acetate and methanol. The methanol extract was evaluated for the antioxidant activity using DPPH radical scavenging method and its antioxidant activity was compared to rutin (positive control). Isolation of the antioxidant compound was performed using preparative thin layer chromatography over silica gel GF₂₅₄ eluted with a mixture of ethyl acetate: acetone: formic acid: water (5:3:1:1). The active compound was obtained as needle like crystals and the structure was characterized by spectroscopic methods as kojic acid which has never been reported as a constituent of this plant. Methanol extract showed to have DPPH scavenger activity with the IC₅₀ 12.63±0.09μg/mL, weaker than rutin (IC₅₀=3.49±0.006μg/mL). Kojic Acid is a new compound from the methanol extract of senggugu’s root bark which has very strong antioxidant activity.