Isolation, purification and characterization of quercetin from Cucumis sativus peels; its antimicrobial, antioxidant and cytotoxicity evaluations.

The peels of C.s ativus are produced in large quantities in food processing industries and as kitchen-waste, resulting into tremendous loss of valuable bioactive components. Considering this, the flavanoids from C.s ativus peels (CSP) were isolated and characterized by the column chromatography, high-performance thin-layer chromatography (HPTLC), Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) methods. The antioxidant and antibacterial activity of CSP extract against Escherichia c oli , Streptococcus mutans and Pseudomonas aeruginosa was assessed. Scanning electron microscopy (SEM) was also used to investigate the killing efficacy of CSP extract against selected bacterial strains. Cytotoxic activity of extract was analyzed on L929 (connective tissue, Mouse, Mus Muscular) cell lines to check their viability. According to the results, total flavanoid content in CSP extract was found as 55.3 ± 1.154 µg/g QE and the chromatographic and spectral data of the isolated compound was elucidated as quercetin-a flavanoid. The CSP extract has also found to give significant antioxidant activity for both DPPH (2, 2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assay. The CSP extract was found to inhibit growth of E. c oli , P. aeruginosa and S. mutans by forming inhibitory zones of 11.36 ± 0.47, 6.7 ± 0.36 mm and 10.16 ± 0.11 mm, respectively. The SEM results also confirm the rupturing of cells or biofilms of bacterial cells as compare to control strains. Additionally, CSP extract was found to not inhibit the proliferation of L929 cells and more than 90% viability of cells was achieved. The present finding highlights the phytochemical profile and therapeutic applications of C.s ativus peels.