Secondary Metabolites from The Active Antioxidant Fraction of The Stem Bark of Syzygium zeylanicum. L. DC.

Syzygium zeylanicum (L.) DC, known by the local community in South Sumatra, Indonesia, as jambu nasi-nasi. This plant has been used to treat various diseases including hypertension, diabetes, joint pain, headaches, and fever. The use of plants as medicine is closely related to their secondary metabolite content. This research is an experimental study aimed at determining the antioxidant activity of fractions from the stem bark of S.zeylanicum and isolating and determining the chemical structure of its active compounds. The fractionation of the dry powder of S. zeylanicum stem bark was carried out using a gradient extraction method with solvents n-hexane, ethyl acetate, and methanol. Each fraction was tested for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The active antioxidant fractions were further isolated into pure compounds using chromatography techniques, and their chemical structures were identified through spectroscopy, including 1D and 2D Nuclear Magnetic Resonance (NMR). The antioxidant activity test results (IC50) for each fraction, namely n-hexane, ethyl acetate, and methanol, were 338.1: 114.1: and 88.71 µg/mL. The results of the separation of the ethyl acetate and methanol fractions using a chromatography column showed that the SE7 subfraction from the ethyl acetate fraction had the highest IC50, which is 83.25 µg/mL. The SE7 fraction was further separated by column chromatography until compound 1 was obtained as a white solid with an IC50 value of 62.22 µg/mL. Based on spectroscopic analysis including 1H-NMR, 13C-NMR, HSQC, HMBC and UV, compound 1 is proposed as 1-(4-isopropoxyphenyl)propane-1,2,3-triol