Essential Oil of Symplocos chinensis (Lour.) Druce: Chemical Composition, Antioxidant Activity, and Inhibitory Effects on Acetylcholinesterase and β-Lactamase

In traditional Chinese medicine, Symplocos chinensis (Lour.) Druce is a well-known herbal remedy prescribed to treat malaria, snakebites, and thermal injuries (burns and scalds). The objective of this study was to characterize the volatile profile of S. chinensis essential oil (EO) and evaluate its therapeutic potential through antioxidant, acetylcholinesterase (AChE), and β-lactamase inhibitory assays. The major components of S. chinensis EO included squalene (12.08%), octanol (7.01%), edulan III (6.81%), n-Hexadecanoic acid (6.81%), geranylacetone (4.80%), β-longipinene (4.60%), 2-methyl-1-octene (2.55%), (E, E)-2,4-decadienal (2.15%), and linalool (2.00%). Antioxidant evaluation revealed that the S. chinensis EO possessed relatively moderate radical scavenging properties, achieving 39.6% inhibition of DPPH radicals at 10 mg/mL, while its activity against ABTS radicals yielded an IC50 of 6.85 ± 1.97 mg/mL. Its reducing power, as determined by the FRAP assay, was further quantified at 175.50 ± 23.25 µmol/g. Furthermore, the EO exhibited inhibitory activities against AChE (IC50 = 149.40 ± 16.92 μg/mL) and β-lactamase (IC50 = 30.20 ± 0.84 μg/mL). These results demonstrate that S. chinensis EO exhibits antioxidant, AChE-inhibitory, and β-lactamase-inhibitory activities in vitro, warranting further comprehensive, systematic studies to evaluate its biological properties and potential applications.