Chemical Composition and Antimicrobial Activities of the Essential Oil Extracted from the Leaves of Phrynium tonkinense Gagnep

Objective: The genus Phrynium has medicinal value and is effective in relieving sore throat and mouth ulcers. However, the extraction and chemical analysis of essential oils from Phrynium tonkinense Gagnep, have not yet been reported. The present study aimed to extract, chemically characterize, and evaluate the antimicrobial properties of volatile oils from Phrynium tonkinense Gagnep (P. tonkinense). Methods: In the present study, essential oil was extracted from the leaves of P. tonkinense for the first time by the hydrodistillation method, and its chemical composition was determined by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The area normalization method was used to calculate the relative percentage content of each chemical constituent in the essential oil. Additionally, the antibacterial efficacy of the essential oil was tested against six pathogenic microorganisms by the agar diffusion method and the microdilution method. Result: The yield of essential oil obtained by hydrodistillation was 0.499%. Ninety volatile components were identified from the essential oil, with fatty acid compounds (47.36%) accounting for the largest proportion of these components. The main compounds were hexadecanoic acid (25.20%), (Z)-3-hexen-1-ol (10.31%), pentadecanoic acid (8.09%), and myristic acid (3.99%). The results of the in vitro antimicrobial assay showed that essential oils from P. tonkinense had a good inhibitory effect on the six selected pathogenic microorganisms and showed good bactericidal activity, with the minimum inhibitory concentration (MIC) value ranging from 31.3 to 250 mu g/mL and the minimum bactericidal concentration (MBC) value ranging from 62.5 to 500 mu g/mL. Notably, the essential oil exhibited the highest antibacterial activity against Staphylococcus aureus, with the MIC of 31.3 mu g/mL and the MBC of 62.5 mu g/mL. Conclusion: The findings of this study provided new insights into the medicinal functions of P. tonkinense and offered a scientific basis for the development and utilization of P. tonkinense as a natural antibacterial agent.