Antibacterial efficacy of essential oils from Eugenia javanica Lam. and Eugenia paniala Roxb. leaves against Staphylococcus chromogenes and Streptococcus uberis for dairy mastitis

The aim of this research was to explore the antibacterial properties of essential oils derived from the leaves of Eugenia javanica Lam. (E. javanica Lam.) and Eugenia paniala Roxb. (E. paniala Roxb.) against prevalent mastitis-causing bacteria such as Staphylococcus chromogenes (S. chromogenes) and Streptococcus uberis (S. uberis). These oils were extracted from the leaves of E. javanica Lam. and E. paniala Roxb. using hydrodistillation with a Clevenger-type apparatus. Subsequently, the chemical compositions of the crude oils were determined using gas chromatography-mass spectrometry. The yield of the essential oil was found to be 0.05 ± 0.01% (w/w) and 0.12 ± 0.01% (w/w) on a fresh weight basis. The primary compounds identified consisted of γ-Terpinene (30.78%), p-Cymene (12.28%), (E)-Caryophyllene (8.84%), and β-Pinene (8.18%) for E. javanica Lam., while trans-β-ocimene (57.29%), trans-caryophyllene (7.42%), linalool (4.60%), and caryophyllene oxide (3.85%) were the predominant constituents for E. paniala Roxb. The antibacterial activity of each essential oil was assessed through minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) using the broth microdilution method. The MIC and MBC values of the essential oils from E. javanica Lam. and E. paniala Roxb. leaves against each pathogen were compared using the Mann-Whitney U test for pairwise analysis. The results revealed that the essential oil from E. paniala Roxb. leaves exhibited superior inhibitory and bactericidal effects against S. chromogenes with lower MIC and MBC values (P < 0.05). In summary, essential oils extracted from E. javanica Lam. and E. paniala Roxb. leaves demonstrated antibacterial activity against major mastitis pathogens, including S. chromogenes and S. uberis.