Screening the Physical Properties, Chemical Profile and Antimicrobial Activity of Five Essential Oils

Given the global challenge of drug-resistant pathogens, essential oils would be new pharmacological supplements for antibacterial action with low toxicity and low or no resistance. This study investigated the physical properties, chemical profile and antimicrobial activity of native essential oils to develop antibiotic alternatives. Specifically, essential oils were extracted from Dendranthema indicum, Orixa japonica, Chamaecyparis pisifera var. filifera, Peucedanum japonicum, and Pinus strobus using hydrodistillation. The antimicrobial activity of essential oils against Staphylococcus aureus and Klebsiella pneumonia was assessed by Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). The essential oils from D. indicum with blue colour showed lower b* values (3.21±0.78) than other species (14.94±0.51-15.84±0.78). D. indicum oil showed the highest values in relative density (0.920±0.000g/mL) and refractive index (1.493±0.000nD²⁰) among the other oils. These results might be attributed to the major component of camphor in oils, known for its high density and refractive index. C. pisifera had the highest oil yield (4.01±0.17% DW) among the other species (0.36 ± 0.13-0.78±0.18% DW). Both C. pisifera and P. japonicum oils were rich in monoterpenes (81.09-91.06%), such as 3-carene (34.28%) and β-pinene (47.37%). Yet, the other oils were abundant in sesquiterpenes (13.82-36.45%). For example, the major components of D. indicum oils were germacrene-D (16.56%), followed by caryophyllene (9.20%). D. indicum and O. japonica oils were particularly effective in inhibiting both bacterial growths (MIC:0.5-1.5% and MBC:4-8%), whereas the other essential oils might require higher concentrations for bactericidal effects (MIC:1-3% and MBC:3- ≥ 12%). The strong antibacterial effect of D. indicum and O. japonica oils might be attributed to the major components of camphor (23.05%) and linalool (10.92%), respectively. Therefore, D. indicum and O. japonica essential oils would exhibit strong antibacterial activity, highlighting a potential antimicrobial agent in food and health industrial resources.