Abstract
The purpose of this study was to investigate the essential oil composition, phytochemicals, and antibacterial activity from the leaves of P. rostratum. Essential oil was obtained from the leaves of P. rostratum by hydrodistillation, and its chemical compositions were determined using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Soxhlet extraction was performed successively on the leaves using n-hexane, ethyl acetate, and methanol. Next, the isolation of phytochemicals was carried out via silica gel column chromatography. The chemical structures of isolated compounds were determined using spectral analysis and comparison with literature data. Antibacterial activity was analysed using micro dilution method. The results showed that twenty components (94.2%) were identified in the leaf oil with _-muurolene (14.1%), _-cadinene (13.2%), allylpyrocatechol diacetate (11.5%), chavicol (8.2%), _-humulene (7.8%), and hydroxychavicol (6.9%) as major components. Meanwhile, eight compounds were isolated from the leaf extracts, including 4'-hydroxy-3',5',5,7-tetramethoxyflavone, 5,7-dimethoxyflavone, 4',5,7-trimethoxyflavone, 3',4',5,7-tetramethoxyflavone, 3_,4_,5_,5,7- pentamethoxyflavone, and 5-hydroxy-3',4',7-trimethoxyflavone, _-sitosterol, and stigmasterol. Besides, 5-hydroxy-3',4',7-trimethoxyflavone demonstrated the strongest antibacterial activity with MIC value of 25 _g/mL against Staphylococcus aureus, Bacillus cereus, and Escherichia coli. In conclusion, sesquiterpenes are the major components of the essential oil, and six flavonoids along with two terpenes were isolated with one compound displayed potential antibacterial activity, all of which are reported for the first time from P. rostratum leaves. These findings highlight the potential of Piper species as natural plant-based antibacterial agents and contribute for future drug research.