engleski

PHYTOCHEMICAL ANALYSIS AND EVALUATION OF ANTIOXIDANT, ANTIMICROBIAL, AND ANTIPROLIFERATIVE ACTIVITIES OF A. cepa L. AND A. × cornutum CLEMENTI EX VISIANI, 1842 PEEL EXTRACTS

Background: Members of the genus Allium are known as one of the most important cultivated plants in the world. A. cepa and A. × cornutum Clementi are edible species that have been used in human nutrition and traditional medicine for years. Annual production and consumption of these species has increased by more than 70% in the last decade, generating more than 500, 000 tons of onion waste annually. There is a growing need for efficient disposal of this waste in the environment. It should be emphasized that onion waste is a rich source of bioactive compounds that have a range of biological activities that could be used in the food and pharmaceutical industries. Objective: To identify the major bioactive components in onion peel extracts and analyze their antioxidant, antimicrobial, and antiproliferative activities. Methods: High-performance liquid chromatography (HPLC) analysis was used to identify the major flavonoids and anthocyanins. The antioxidant activity of the onion peel extracts was tested by two methods, 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC). The antimicrobial activity on eleven strains of human opportunistic pathogens and food spoilage microorganisms was determined by broth microdilution assay. MTS cell proliferation assay was performed on three cancer cell lines, cervical cancer cell line (HeLa), human colon cancer cell line (HCT116), and human osteosarcoma cell line (U2OS), without and after in vitro digestion of onion waste extracts. Results: Quercetin 3, 4′-diglucolside, quercetin 4′-monoglucoside and quercetin are the major flavonols in onion extracts. The composition of anthocyanins varied in all extracts tested. DPPH and ORAC assays showed that the from the A. × cornutum peel extract had the strongest antioxidant activity. The extract from A. × cornutum also exhibited the strongest antimicrobial activity. Comparable antiproliferative activity was confirmed for all onion extracts tested on cancer cell lines. Conclusion: The results show the enviable biological activity of onion waste extracts. Considering the huge amount of onion peel waste, which is a global environmental and economic problem, new research, such as the one conducted in this study, could pave the way for the use of onion waste in the pharmaceutical, food or cosmetic industries.

Allium × cornutum Clementi ex Visiani ; 1842 ; Allium cepa L. red and yellow variety ; flavonols ; anthocyanins ; antioxidant properties ; antimicrobial and antiproliferative activity

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