Chemical Composition, Antibacterial, Anti-Inflammatory, and Enzyme Inhibitory Activities of Essential Oil from Rhynchanthus beesianus Rhizome.

Rhynchanthus beesianus W. W. Smith, an edible, medicinal, and ornamental plant, is mainly cultivated in China and Myanmar. The essential oil (EO) from R. beesianus rhizome has been used as an aromatic stomachic in China. The chemical composition and biological activities of EO from R. beesianus rhizome were reported for the first time. Based on gas chromatography with flame ionization or mass selective detection (GC-FID/MS) results, the major constituents of EO were 1,8-cineole (47.6%), borneol (15.0%), methyleugenol (11.2%), and bornyl formate (7.6%). For bioactivities, EO showed a significant antibacterial activity against Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Proteus vulgaris with the diameter of the inhibition zone (DIZ) (8.66-10.56 mm), minimal inhibitory concentration (MIC) (3.13-6.25 mg/mL), and minimal bactericidal concentration (MBC) (6.25-12.5 mg/mL). Moreover, EO (128 μg/mL) significantly inhibited the production of proinflammatory mediators nitric oxide (NO) (92.73 ± 1.50%) and cytokines tumor necrosis factor-α (TNF-α) (20.29 ± 0.17%) and interleukin-6 (IL-6) (61.08 ± 0.13%) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages without any cytotoxic effect. Moreover, EO exhibited significant acetylcholinesterase (AChE) inhibitory activity (the concentration of the sample that affords a 50% inhibition in the assay (IC50) = 1.03 ± 0.18 mg/mL) and moderate α-glucosidase inhibition effect (IC50 = 11.60 ± 0.25 mg/mL). Thus, the EO could be regarded as a bioactive natural product and has a high exploitation potential in the cosmetics and pharmaceutical industries.