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Antioxidant and antibacterial studies of ginger (Zingiber officinale L.) rhizome and garlic (Allium sativum L.) cloves extracts

Student name: Ms Swati Singh
Guide: Dr Ramakrishnan Sitaraman
Year of completion: 2018
Host Organisation: School of Biochemical Engineering, IIT, BHU, Varanasi
Supervisor (Host Organisation): Dr Abha Mishra
Abstract: Natural products, especially plants, are known to possess medicinal properties. The current study focuses on two prominent spices - Zingiber officinale (ginger) and Allium sativum (garlic) – that are traditionally known for their medicinal properties. In order to analyse their medicinal potential, two types of extracts – aqueous and methanolic – were prepared from cloves of garlic, ginger rhizomes and one ginger-garlic homogenized mixture (1:1) were made. The extracts were characterized using Thin-layer chromatography, High-performance liquid chromatography and Fourier-transform infrared spectroscopy and investigated for their antimicrobial activity, against four local clinical bacterial isolates viz. Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Antimicrobial activity was evaluated using the disc diffusion method and antioxidant activity was determined by Ferric reducing antioxidant power (FRAP) assay. Ginger and garlic were found to contain terpenoids, tannins, alkaloids, saponins, steroids, phenols, volatile oils and fats. It was found that the total flavonoid content and total phenolic content of the ginger-garlic methanol extract was highest among all the other organic and aqueous extracts and hence, may be the reason to show highest anti-oxidant property. It was observed that the clinical isolates of both Gram-positive and Gram-negative bacteria were sensitive to all tested aqueous and methanolic extracts. Interestingly, the Gram-positive bacteria were more sensitive than the Gram-negative bacteria. Moreover, it was noticed that ginger-garlic methanol extract shows better antibacterial activity as compare to other five extracts.

Keywords: Ginger; garlic; antimicrobial; antioxidant; phytochemicals