Lemon myrtle and Kayu manis essential oils: Bioactive compounds, antimicrobial, antioxidant, and toxicity profiles.

Abstract

Essential oils are known for their diverse therapeutic properties, including antibacterial and antioxidant activities. This study evaluates the chemical composition, antimicrobial activity, antioxidant, and toxicity profiles of Lemon myrtle (Backhousia citriodora) and Kayu M\manis (Cinnamomum cassia) essential oils. The chemical compositions of the essential oils were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Antimicrobial activity was assessed through the broth microdilution method against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Bacillus cereus, Klebsiella pneumoniae, Escherichia coli, and Candida albicans. Antioxidant activity was measured using the DPPH assay, and toxicity was assessed using the Brine Shrimp Lethality Assay (BSLA). GC-MS analysis revealed that 3,7-dimethyl-2,6-octadienal (57.12%) was the major compound in Lemon myrtle essential oil (LMEO), while Kayu manis essential oil (KMEO) was predominantly composed of Eugenol (71.86%). LMEO exhibited significant antimicrobial activity with MIC values ranging from 250 µg/mL to 500 µg/mL against all the test organisms. In contrast, KMEO showed no activity against S. aureus but demonstrated antimicrobial activity against other bacteria and C. albicans with similar MIC values. The antioxidant activity of LMEO was more potent, with an IC₅₀ of 42 µg/mL, compared to KMEO, which had an IC₅₀ of 216 µg/mL. Toxicity testing revealed mild toxicity for LMEO (LC₅₀ 489 µg/mL) and no toxicity for KMEO (LC₅₀ >1000 µg/mL). LMEO and KMEO displayed promising antimicrobial and antioxidant properties. These findings highlight the potential of these essential oils as natural alternatives for therapeutic and cosmetic applications, with LMEO offering more effective antimicrobial and antioxidant activities.