Anti-bacterial Effect of Essential Oils Extracted from Selected Spices of Zingiberaceae

Background: Plants are rich source of therapeutic phytochemicals used for treating various ailments. In specific, spices are used in Indian and Chinese system of medicine. Although spices are traditionally used as food preservatives besides food color and flavor, their medicinal values remain unrecognized. This paper discusses the antibacterial activities of essential oil samples extracted from selected spices (cardamom, ginger and turmeric) belonging to Zingiberaceae, the ginger family. Methods: The essential oils from rhizomes of ginger (Zingiber officinale R.) and turmeric (Curcuma longa L.) as well as capsules of cardamom (Elettaria cardamom M.) were extracted by hydrodistillation. The oil samples were analyzed by gas chromatography/mass spectrometry (GC/MS). The chemical composition was identified based on the retention index, and also by co-injection with authentic standards. The oil samples were also evaluated for their antibacterial activities. Results: The major composition of cardamom is 1,8-cineole (40.11%) and alpha-terpinyl acetate (39.24%). In the case of ginger, it is dominated by zingiberene (32.01%) followed by beta-sesquiphellandrene (16.25%) and farnesene (12.52%). In turmeric, the major composition is found to be turmerone (32.55%) followed by ar-turmerone (23.15%) and curlone (23%). Besides other compounds such as 1,8-cineole, alpha-curcumene, alpha-terpinene, alpha-thujene, beta-myrcene, beta-sesquiphellandrene, gamma-terpinene, limonene, linalool, terpinolene, (Z)-citral and zingiberene were present in varying levels. Conclusion: The spice oil samples were more effective against Gram positive than Gram negative bacteria. The constituents of cardamom oil are highly antibacterial than ginger and turmeric oils. It was found to inhibit Lactobacillus sp., a probiotic Gram positive bacterium. The probiotic inhibitory potential of essential oils is in the following order: ginger > cardamom > turmeric. Although essential oils are generally recognized as safe, it may potentially inhibit probiotic bacteria. Hence, more research is required in this direction.