Antioxidant Activity of Red Lip (Syzygium myrtifolium Walp.) Leaves Fractions and their Secondary Metabolites

Antioxidant compounds can prevent or delay certain types of cell damage caused by oxidation processes involving oxidants. One of the sources of antioxidant compounds is the red lip plant (Syzygium myrtifolium Walp.). S. myrtifolium is a medicinal plant that has traditionally been used for the treatment of hypertension, facilitating labor, and alleviating abdominal pain. This research was conducted to evaluate the antioxidant activity of fractions derived from S. myrtifolium leaves and to identify the chemical profile of the antioxidant-active fractions. Fractionation of S. myrtifolium leaves was carried out through successive maceration in graded solvents. Each fraction was tested for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Quercetin exhibits very strong antioxidant activity and is used as a standard for comparison. The chemical components with strong antioxidant activity were further separated by gravity column chromatography into several subfractions. The chemical profiles of the active subfractions were identified by using 1D Nuclear Magnetic Resonance (NMR) Spectroscopy and Liquid Chromatography Mass Spectrometry/Mass Spectrometry (LCMS/MS). This study found that ethyl acetate and methanol fractions showed strong antioxidant activity. Separation of the active fractions by gravity column chromatography yielded an active subfraction from the ethyl acetate and the methanol fractions with IC50 values of 99.2 μg/mL and 78.8 μg/mL, respectively. A pure white solid compound was obtained from the active ethyl acetate subfraction, which was identified by 1D NMR spectroscopy as betulinic acid. Furthermore, the active subfraction from the methanol fraction was analyzed by LCMS/MS and identified as containing bergenin, quercetin, elemicin, and asarone.