Chemical Composition and In Vitro Antimicrobial, Antioxidant, and Tyrosinase-Inhibiting Activity of Essential Oils Extracted From the Leaves and Twigs of Calocedrus macrolepis var. formosana

Abstract

In this study, we focused on evaluating the antimicrobial, antioxidant, and tyrosinase-inhibiting properties of leaf and twig essential oils from Calocedrus macrolepis var. formosana. Additionally, we determined the major components associated with these effects. The findings revealed that α-pinene (36.4%) and limonene (23.6%) were the dominant components in the leaf essential oil, while α-pinene (36.2%), ferruginol (22.5%), and limonene (13.1%) were the major constituents in the twig essential oil. However, when comparing the biological activities of the 2 essential oils, the twig essential oil demonstrated excellent inhibitory effects against skin pathogens, as well as strong antioxidant and tyrosinase-inhibiting activities, in contrast to the leaf essential oil. The twig essential oil also exhibited excellent antimicrobial activity against 5 skin pathogenic strains, with the strongest inhibitory effect being that against Staphylococcus aureus, S epidermidis, and Candida albicans, which was accompanied by an inhibition zone of 46 to 48 mm, a minimum inhibitory concentration (MIC) of 125 μg/mL, and a minimum bactericidal concentration (MBC) of 250 μg/mL. The inhibitory activity of the twig essential oil against lipid peroxidation was found to be potent, as evidenced by an IC50 value of 216 ± 1.9 μg/mL. It also exhibited strong scavenging activity against free radicals, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC50 = 121.6 ± 0.5 μg/mL) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC50 = 136.8 ± 1.6 μg/mL) cation radicals. In addition, it exhibited a high cupric ion reducing–antioxidant capacity (CUPRAC), with the A0.50 value determined to be 186.28 ± 0.5 μg/mL. It also exhibited adequate activity in terms of inhibiting in vitro tyrosinase activity, as evidenced by an IC50 value of 168.5 ± 0.6 μg/mL. Further analysis revealed that ferruginol was the active component responsible for the antimicrobial, antioxidative, and tyrosinase-inhibiting activities observed in twig oil. These findings suggest that the twig oil is a promising candidate for further research because of its favorable antimicrobial, antioxidative, and tyrosinase-inhibiting activity.