Assessment of biological activity and physicochemical composition of essential oils from selected Citrus species in Vietnam

Despite the growing interest in natural preservatives and bioactive compounds from plant sources, comparative studies on Citrus peel essential oils-especially those cultivated in Vietnam-remain limited. This study evaluated the chemical composition, physical properties, and biological activities of peel essential oils (EOs) from four Citrus species: orange (Citrus sinensis, CsEO), grapefruit (Citrus grandis, CgEO), lemon (Citrus aurantiifolia, CaEO), and calamondin (Citrus microcarpa, CmEO), all grown in Dong Nai, Vietnam. GC-MS analysis revealed D-limonene as the dominant compound (68.98-85.11%) in all samples. Notably, CsEO contained high α-pinene (24.81%), while CmEO had more α-thujene (13.32%), β-pinene (6.56%), and sabinene (5.39%). Principal component analysis showed CmEO had a distinct chemical profile. Regarding biological activity, CsEO showed the strongest antibacterial effect with a 16.63 mm inhibition zone against E. coli, followed by CaEO and CgEO. CsEO also demonstrated the highest antioxidant activity (IC50-DPPH=183.53 mg/mL), while CmEO had the lowest. Physical characteristics such as acid value, saponification index, and aroma retention also varied among samples. This study presents one of the first comparative analyses of Citrus peel EOs from Dong Nai, emphasizing species-dependent variation and potential application in food, cosmetics, and natural products.