Exploring Antimicrobial Activities of Clove, Tea Tree, Eucalyptus, and Lesser Galangal Essential Oils Against Some Pathogenic Microbes and Their Antioxidant Activities
Dararat Samretwit, PhD¹, Piriyaporn Chongtrakool, PhD², Chanwit Tribuddharat, MD², Ruxjinda Wattanalai, PhD¹, Ampun Chaikulsareewath, MSc³, Piyanoot Noiduang, MSc³, Payud Wongwinyuchon⁴, Pawish Wongwinyuchon⁴, Tronton Lerttamrab⁵, Tanate Suttisaewan, MD⁶, Somporn Srifuengfung, PhD¹
Affiliation : ¹ Faculty of Pharmacy, Siam University, Bangkok, Thailand; ² Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand; ³ Faculty of Science, Siam University, Bangkok, Thailand; ⁴ High school student, King Mongkut’s International Demonstration School, Bangkok, Thailand; ⁵ High school student, Concordian International School, Samut Prakan, Thailand; ⁶ CGH Saimai Hospital, Bangkok, Thailand
Abstract
Background: Many essential oils have antimicrobial and antioxidant activities with potential use in medicine. In Thailand, due to a lack of studies on clove, tea tree, lesser galangal, and eucalyptus oils.
Objective: To determine the inhibitory effect against microbial pathogens, antioxidant activity, and evaluate the chemical components of clove, tea tree, lesser galangal, and eucalyptus oils.
Materials and Methods: Antimicrobial activities which were collected of 46 clinical isolates of methicillin-sensitive and resistant Staphylococcus aureus, Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were determined by the disk diffusion method. Antioxidant activity was performed by DPPH (1,1-diphenyl-2-picryl-hydrazyl) assay.
Results: Clove oil had the most antimicrobial activity, followed by tea tree oil, lesser galangal, and eucalyptus oils, respectively. By DPPH assay, clove oil had the most antioxidant activity, followed by tea tree and lesser galangal oils, respectively. The IC₅₀ of clove, tea tree, and lesser galangal oils were 0.01±0.00, 15.48±0.00, and 34.27±0.21 mg/mL, respectively. Antioxidant activity of eucalyptus oil was not found. Eugenol, alpha-terpineol, and terpinen-4-ol are components abundant in clove, tea tree, and lesser galangal oils, respectively. Antimicrobial activities of these components are indifferent (by mean ± SD) because inhibition zone diameters were 14.40±5.16, 14.02±5.32, and 12.71±5.59 mm, respectively.
Conclusion: The results suggested that clove, tea tree, lesser galangal oils, and their components may benefit new treatment or prevention against microbial infections. For antioxidant activity, eugenol demonstrated the highest inhibition. Following eugenol, alpha-terpineol, a chemical component in tea tree oil, showed significant antioxidant property, and terpinen-4-ol, found in lesser galangal oil, exhibited the least antioxidant capability.
Received 15 August 2025 | Revised 8 March 2026 | Accepted 12 March 2026
J Med Assoc Thai 2026;109(7):604-11
Keywords : Clove oil; Tea tree oil; Lesser galangal oil; Eucalyptus oil; Essential oil
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