Chemical Composition, Antibacterial, and Anti-Inflammatory Activities of Essential Oils from Flower, Leaf, and Stem of Rhynchanthus beesianus

Abstract

Rhynchanthus beesianus is a medicinal, ornamental, and edible plant, and its essential oil has been used as an aromatic stomachic in China. In this study, the chemical constituents, antibacterial, and anti-inflammatory properties of flower essential oil (F-EO), leaf essential oil (L-EO), and stem essential oil (S-EO) of R. beesianus were investigated for the first time. According to the GC-FID/MS assay, the F-EO was mainly composed of bornyl formate (21.7%), 1,8-cineole (21.6%), borneol (9.7%), methyleugenol (7.7%), β-myrcene (5.4%), limonene (4.7%), camphene (4.5%), linalool (3.4%), and α-pinene (3.1%). The predominant components of L-EO were bornyl formate (33.9%), borneol (13.2%), 1,8-cineole (12.1%), methyleugenol (8.0%), camphene (7.8%), bornyl acetate (6.2%), and α-pinene (4.3%). The main components of S-EO were borneol (22.5%), 1,8-cineole (21.3%), methyleugenol (14.6%), bornyl formate (11.6%), and bornyl acetate (3.9%). For the bioactivities, the F-EO, L-EO, and S-EO exhibited significant antibacterial property against Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa, and Escherichia coli with the inhibition zones (7.28-9.69 mm), MIC (3.13-12.50 mg/mL), and MBC (6.25-12.50 mg/mL). Besides, the F-EO, L-EO, and S-EO significantly inhibited the production of proinflammatory mediator nitric oxide (NO) (93.15-94.72%) and cytokines interleukin-6 (IL-6) (23.99-77.81%) and tumor necrosis factor-α (TNF-α) (17.69-24.93%) in LPS-stimulated RAW264.7 cells at the dose of 128 μg/mL in the absence of cytotoxicity. Hence, the essential oils of R. beesianus flower, leaf, and stem could be used as natural antibacterial and anti-inflammatory agents with a high application potential in the pharmaceutical and cosmetic fields.

Figure 1

GC-MS chromatogram of R. beesianus F-EO.

Figure 2

GC-MS chromatogram of R. beesianus L-EO.

Figure 3

GC-MS chromatogram of R. beesianus S-EO.

Figure 4

Effects of F-EO, L-EO, and S-EO on cell viability of RAW264.7 (a) and L929 (b) cells. The data were presented as mean ± standard deviation (SD) of three independent experiments. ^∗p < 0.05, compared to untreated control group cells.

Figure 5

Effects of F-EO, L-EO, and S-EO on the LPS-induced RAW264.7 cell morphology (128 μg/mL) (a), NO production (b), and secretion of IL-6 (c) and TNF-α (d). The results of at least three independent experiments were expressed as mean ± SD values. (b-d) Different letters above bars represent a significant difference (p < 0.05).