Extraction Processing Technologies and Their Effects on Antioxidant Activity in Cinnamomum camphora (L.) J. Presl Leaves

This study investigated the bioactive potential of Cinnamomum camphora (L.) J. Presl (C. camphora) leaf extracts obtained using hydrothermal extraction (HE) and ultrasound-assisted extraction (UAE) with 30%, 50%, and 70% ethanol (v/v). Extracts were analyzed for their phytochemical composition and biological activities. UAE extracts, particularly with 70% ethanol, exhibited the highest total polyphenol (363.0 ± 1.40 mg GAE/g) and flavonoid (174.5 ± 0.42 mg QE/g) contents. This extract also demonstrated strong antioxidant activities (IC50: 0.024 ± 0.001 mg/mL for DPPH; IC50: 0.363 ± 0.002 mg/mL for ABTS; 3.080 ± 0.044 M Fe2+/g for FRAP) and potent enzyme inhibition (49.3 ± 0.35% for tyrosinase; 24.8 ± 0.34% for elastase; 94.5 ± 0.12% for α-glucosidase and 77.5 ± 1.11% for lipase). Antimicrobial activity was most effective against Gram-positive bacteria, notably against Cutibacterium acnes, showing the largest inhibition zone (23.0 mm at 10 mg/disc). Overall, antioxidant, enzyme inhibition and antimicrobial activities increased significantly with increasing ethanol concentration, particularly at 70% ethanol. GC–MSD analysis revealed that both HE and UAE extracts contained phenolic acids, terpenes, triterpenes, and sesquiterpenes. Collectively, these findings indicate that the extraction method (UAE) and solvent composition (70% ethanol) influence the bioactivity profile of C. camphora leaf extracts, supporting further investigation of their relevance for cosmeceutical and functional applications.