Syzygium myrtifolium Walp leaves have antibacterial and natural colourant potential, which are beneficial for health. The purpose of this study was to optimize flavonoid, anthocyanin levels, and antibacterial bioactivity of red shoot leaves with various extraction solvents. Extraction was carried out by maceration using 3 solvents with varying solubility: 70% ethanol, ethyl acetate, and n-hexane. The extract obtained was measured for flavonoid content at 440 nm using UV-Vis spectrophotometry. Anthocyanin content was measured at 510 nm and 700 nm using buffers at pH 1 and 4.5. Antibacterial testing used the paper disk diffusion method, with a negative control using solvent and a positive control using chloramphenicol. The study showed that flavonoid and anthocyanin levels in the ethanol extracts were 24.3 mgEK/g and 1.38 mg/L, respectively. The test results at concentrations of 1, 4, 8, and 16% were best obtained with n-hexane extracts, with inhibition strength values ranging from strong to very strong against Staphylococcus aureus (17.25, 20.02, 21.53, and 26.38 mm). For Escherichia coli, the inhibitory strength values ranged from strong (10.44, 13.05, 13.43, and 15.27 mm). This study concludes that solvent variation affects the flavonoid and anthocyanin content and the antibacterial bioactivity of S. myrtifolium leaf extract.
Imrawati et al. (Sun,) studied this question.
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