Chemical Compositions and In Vitro Antioxidant Activities of the Essential Oils of Sawdust and Resin-Rich Bark from Azorean Cryptomeria japonica (Cupressaceae)

Abstract

In the Azores archipelago (Portugal), forest operations and wood industry generate large amounts of Cryptomeria japonica biomass residues (CJBR), which can be used to produce valuable essential oils (EOs). In this study, we evaluated the chemical composition and antioxidant activities of EOs from Azorean C. japonica sawdust (CJS) and resin-rich bark (CJRRB). The CJS and CJRRB EOs, obtained via hydrodistillation, showed different yield values (0.27% vs. 0.80% v/w, dry weight) and also different chemical profiles, as assessed using GC/MS. A total of 64 and 85 components were identified in CJS and CJRRB EOs, representing 95.7% and 96.9% of the total composition, respectively. The major components in CJS EO were oxygenated sesquiterpenes (mainly α+β-eudesmol, 1-epicubenol, and cubebol), while in CJRRB EO, the major components were monoterpene hydrocarbons, including α-pinene, δ-3-carene, and limonene (66.6% vs. 6.4% for oxygenated sesquiterpenes and 0% vs. 64% for monoterpene hydrocarbons, respectively). Antioxidant activity was estimated using (i) two radical-based assays, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity, and (ii) a lipid model assay, β-carotene-linoleic acid bleaching activity (BCBA). Both CJS and CJRRB EOs exhibited concentration-dependent antioxidant activities, and their DPPH, ABTS, and BCBA EC50 values were 1107 vs. 1275 µg/mL, 260 vs. 498 µg/mL, and 1764 vs. 662 µg/mL, respectively. The results indicate that both EOs were able to exert antioxidant activity via different mechanisms of action. Therefore, Azorean CJS and CJRRB may be sustainable sources for antioxidant compounds. This study expands the chemical and biological knowledge of CJBR EOs and, consequently, adds more value to the C. japonica EO industry.