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

This study investigated the bioactive potential of <i>Cinnamomum camphora</i> (L.) J. Presl (<i>C. camphora</i>) leaf extracts obtained using hydrothermal extraction (HE) and ultrasound-assisted extraction (UAE) with 30%, 50%, and 70% ethanol (<i>v</i>/<i>v</i>). 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 <i>Cutibacterium acnes</i>, 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 <i>C. camphora</i> leaf extracts, supporting further investigation of their relevance for cosmeceutical and functional applications.