Effect of Extraction Method on Yield, Chemical Composition and Antimicrobial Activity of Essential Oil from the Fruits of Amomum villosum var. xanthioides

In this study, the essential oils obtained from the fruits of Amomum villosum var. xanthioides by three different extraction methods (hydrodistillation, steam distillation, and microwave-assisted hydrodistillation) were reported for their yield, chemical composition and antimicrobial activity. The oils obtained were analysed using gas chromatography and gas chromatography-mass spectrometry. Furthermore, the antimicrobial activity of essential oils was evaluated using a microdilution broth assay. The results revealed that the microwave-assisted hydrodistillation produced 2.02% (w/w) yield of oil compared to 1.77% from hydrodistillation and 1.50% from steam distillation. There were significant differences in the content of main components in the essential oils obtained from the different extraction methods. Overall, bornyl acetate (30.01% - 38.18%), camphor (17.53% - 20.91%), borneol (9.21% - 14.68%), D-limonene (6.61% - 9.67%), camphene (4.14% - 8.51%), and β-myrcene (3.85% - 5.16%) were the main components in all the oil samples. The highest amounts of borneol, bornyl acetate, and camphor were obtained from the microwave-assisted hydrodistilled oil. In addition, the essential oil samples were tested for antimicrobial activity and were shown to inhibit the growth of Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa, with minimum inhibitory concentration (MIC) ranging from 100 to 200 μg/mL, and the microwave-assisted hydrodistilled oil exhibited higher antimicrobial activity. In summary, this research revealed that microwave-assisted hydrodistillation is an outstanding method of extracting essential oils from the fruits of A. villosum var. xanthioides.