Chemical composition, antifungal and antioxidant properties of seasonal variation in Eucalyptus tereticornis leaves of essential oil

Abstract

Abstract The study aims to evaluate the chemical composition and anti-microbial activities of essential oils (EOs) extracted from fresh and shed dried leaves of Eucalyptus tereticornis clone C-83 during three consecutive seasons - winter, summer and rainy to determine the best harvesting time for obtaining the highest essential oil yield. The chemical composition was analyzed using a Gas Chromatography–Mass Spectrophotometry (GC-MS) and major compounds in fresh leaves oil were Eucalyptol (54.88%), Camphene (30.40%), α-Eudesmol (22.44%) and 3-Carene (19.50%). Dry leaf oil predominantly comprised Isopulegol (53.53%), 3-Isopropenyl-6-methyl-1-cyclohexene (17.29%) and Cis-Sabinene hydrate (13.55%). Isoterpinolene held a substantial presence at 5.61%, while Guaiol notably contributed at 2.49%. 2-isopropyl-4-methyl-2,5-dihydrooxazole registered at 2.32%, indicating its significant presence in the analyzed composition. Additionally, Bicyclogermacrene and Bicyclo[5.2.0]nonane, 2-methylene-4,8,8-trimethyl-4-vinyl-, exhibited noticeable percentages at 1.43% and 1.32%, respectively, underscoring their relative abundance within the sample. It revealed a concentration dependent rise in antioxidant effectiveness, with summer consistently exhibiting the highest radical scavenging potential of 93.58% at 4% concentration. Additionally, the oil showed antifungal properties against four plant-damaging fungi- Magnaporthe grisea, Rhizoctonia solani, Rhizoctonia bataticola and Fusarium oxysporum- signifying potent antifungal properties in eucalyptus oils. The radical scavenging activity with increasing concentration across all seasons, showcasing higher efficacy as the concentration of essential oil rises, with the summer season consistently displaying the highest antioxidant potential across all concentrations. The study enhances comprehension of EOs and offers a pharmacological analysis, potentially advancing its exploration as a functional drug in agricultural and cosmetic sectors.