Isolation and characterization of marker compounds from the leaves of allium cepa linn. and study of their biological activities

Abstract

The work in thesis describes the isolation and characterization of Amaryllidaceae plant such as Allium cepa is enriched with important biologically active compounds. Previously some work has been reported on the species, but chemical investigation on the species grown in Bangladesh has not been studied extensively. As the plant is being used in our country as a herbal medicine, it is necessary to have a knowledge of the constituents of the plant of our native species. From the profound interest of these compounds and their useful biological activities, the leaves of Allium cepa were extracted with methanol. Then the methanol extract was partitioned with n-hexane, ethyl acetate and 1-butanol, respectively. The partitioned extracts were subjected to various chromatographic techniques to isolate the pure compounds for characterization and determination of their biological activities. Two compounds kaempferol and quercetin were isolated from the ethyl acetate part. All the structures of the compounds isolated from the plant are as follows:

Kaemperol(T-B-S-1)

Quercetin(T-B-S-3)

The above structures of the compounds were elucidated by various spectroscopic methods (UV, FTIR, 1H-NMR, 13C-NMR etc.) and comparison of their spectral data with those published in the literature. The compounds Kaempferol (compound T-B-S-1) and Quercetin (compound T-B-S-3) were found to be isolated and elucidated for the first time according to the literature survey. Compound (T-B-S-1) and (T-B-S-2) were identified as flavonoide

The compounds kaempferol and quercetin were found to have high anti-oxidant activity. One bacterial strains were taken to study the antibacterial activity of the pure compounds; compound (T-B-S-1) and compound (T-B-S-3) at a concentration 20μl/disc. These compounds showed moderate activity against E-coli bacteria. T-B-S-1 pure compound is found sensitive and T-B-S-3 is found resistant against E.coli

Thus the isolation, characterization and investigation of potent antioxidant and antimicrobial activity of the compounds might generate much synthetic and biological interest in this class of the natural products.