Dimocarpus longan (longan) is a tropical fruit commonly cultivated in China, Vietnam, and Thailand. The pulp, seed, flower, twig, and pericarp of longan have been extensively studied but the peel is often discarded as waste and remain underexplored. The extracts of longan peel were prepared using green solvents (methanol, ethanol, and ethyl acetate). The phytochemical profile of the extracts was screened by the thin layer chromatography (TLC) analysis. The antibacterial activity of the extracts was determined by the disk diffusion method and Minimum Inhibitory Concentration (MIC). The TLC analysis showed that the ethyl acetate extract possessed the most phytochemicals (phenolic compounds, flavonoids, tannins and steroids) compared to the methanol and ethanol extracts. All the extracts exhibited comparable antibacterial activity against Bacillus cereus (B. cereus) where the diameters of inhibition zones were ~ 9.01-9.77 mm. The MIC values for methanol and ethanol extracts were 1 mg/mL, however, the MIC value of the ethyl acetate extract could not be determined because the high water content in the broth caused sample precipitation. In summary, the longan peel extracts show potential as natural antibacterial agents against B. cereus.
Chong et al. (Mon,) studied this question.