Chemical Composition and Bioactivity of Essential Oils Extracted from <i>Cinnamomum insularimontanum</i> Hayata Leaves, Twigs, and Fruits

Objective/Background Cinnamomum insularimontanum Hayata, an endemic Taiwanese tree species, has leaves and fruits rich in essential oils that have been traditionally used for medicinal purposes. This study aimed to analyze the chemical composition of essential oils extracted from the leaves, twigs, and fruits, and to evaluate their in vitro antimicrobial, antioxidant, and tyrosinase-inhibiting activities for potential applications in natural preservation and health-related industries. Methods Essential oils were extracted through hydrodistillation and analyzed using GC-FID and GC-MS. Antibacterial, antifungal, antioxidant (β-carotene bleaching, DPPH, ABTS, CUPRAC), and tyrosinase inhibition activities were assessed. Major components were further examined for their contributions to bioactivity. Results The highest yield was obtained for the fruit essential oil (4.52 ± 0.03 mL/100 g), which also showed the strongest bioactivity. It exhibited strong antibacterial activity against Bacillus cereus , Staphylococcus aureus , and S. epidermidis (MIC = 32 μg/mL) and antifungal effects against Aspergillus flavus , A. niger , and Chaetomium globosum (MIC = 64-128 μg/mL). The fruit oil also had the highest antioxidant activity in the β-carotene–linoleic acid bleaching assay, with an IC 50 value of 138.9 ± 1.5 μg/mL, indicating strong inhibition of lipid peroxidation. In the DPPH and ABTS assays, it showed IC 50 values of 92.6 ± 0.5 and 105.2 ± 0.5 μg/mL, respectively. In the CUPRAC assay, it had an A 0 . 50 value of 203.2 ± 0.5 μg/mL, indicating high reducing power. Additionally, it exhibited strong tyrosinase inhibition (IC 50 = 137.4 ± 4.1 μg/mL). Citral, the main component of the fruit essential oil (52.2%), was identified as the key cause of these effects. Conclusion Cinnamomum insularimontanum fruit oil exhibits strong antimicrobial, antioxidant, and tyrosinase-inhibiting effects, mainly due to its high citral content. These findings suggest its promising potential as a natural preservative and functional ingredient in the food, cosmetic, and pharmaceutical industries. Further studies on their mechanisms of action and formulation potential are warranted.