Research on chemical composition and biological activities of essential oil extracted from Lethariella cladonioides (L. cladonioides.) via microreactor technology

Microreactor technology has demonstrated significant advantages in natural product extraction due to its superior mass transfer efficiency. This study optimized the extraction of essential oil from L. cladonioides leaves using a continuous flow microreactor through Box-Behnken experimental design. An extraction yield of 1.81% was achieved under optimal conditions (74 μm powder, 43°C, 2.5 h, ethanol solvent). GC-MS analysis identified 29 compounds accounting for 97.59% of total content, predominantly terpenoids (91.33%), with α-pinene (24.88%), β-pinene (19.65%), and p-mentha-1,8-diene (16.97%) as major constituents. Eight compounds, previously unreported, were detected in this study. The essential oil demonstrated potent antibacterial activity against Gram positive (S. aureus MIC = 1.4 μL/mL), Gram negative (E. coli MIC = 1.5 μL/mL) bacteria, and fungi (C. albicans MIC = 1.7 μL/mL), exhibiting superior antifungal efficacy compared to amoxicillin. Antioxidant assays revealed moderate DPPH radical scavenging capacity (IC50 = 37.69 μg/mL) and β-carotene/linoleic acid system inhibition (IC50 = 0.77 mg/mL). Antibacterial mechanisms involved disruption of cell membrane integrity, as evidenced by extracellular nucleic acid leakage. Cytotoxicity testing confirmed safety for HEK293T cells at concentrations ≤ 50 μg/mL. These findings demonstrate that microreactor extracted L. cladonioides essential oil represents a natural antimicrobial and antioxidant agent with low cytotoxicity, demonstrating promising applications. Keywords: Lethariella cladonioides (L. cladonioides), Essential oil, Composition identification, Antibacterial activity, Continuous flow microreactor