Comprehensive Phytochemical Analysis and Evaluation of Antioxidant, Antimicrobial, Cytotoxic, and Immunomodulatory Activities of Commercial Cinnamon Bark Essential Oil (Cinnamomum zeylanicum L.)

The essential oil derived from the bark of <i>Cinnamomum zeylanicum</i> L., <i>Lauraceae</i>, has gained significant attention because of its numerous biological benefits. This study aimed to perform a phytochemical analysis of commercially available <i>Cinnamomum zeylanicum</i> bark essential oil and to evaluate its antioxidant, antimicrobial, immunomodulatory, and antitumor properties. GC-MS analysis was employed to determine the phytochemical composition. The major component of the total essential oil composition was (<i>E</i>)-cinnamaldehyde, constituting 77.93%, followed by eugenol (4.34%), <i>E</i>-caryophyllene (3.68%), and linalool (2.79%). The antioxidant activity was confirmed by DPPH, ABTS, CUPRAC, and TAC assays. In the broth microdilution assay, cinnamon essential oil demonstrated strong antimicrobial activity, with MIC values ranging from 7.37 to 29.50 µg/mL. Furthermore, cinnamon essential oil demonstrated selective antitumor activity by inducing apoptosis and cell-cycle arrest in human colorectal cancer cells (HCT116) while sparing non-cancerous cells (MRC-5). In HCT116 cells, cinnamon essential oil induced apoptosis, downregulated Cyclin D and p-AKT, and caused G1-phase arrest. Additionally, cinnamon essential oil modulated immune responses by reducing pro-inflammatory cytokine production in activated splenocytes and enhancing pro-inflammatory activity in naïve cells. These findings highlight the great potential of the cinnamon bark essential oil in the development of new therapeutic agents.