Phenolic constituents, antioxidant, antimicrobial and anti-proliferative activities of different endemic Italian varieties of garlic (Allium sativum L.)

Extracts of the bulbs of Italian ecotypes of Allium sativum were analysed to determine their phenolic profiles, antioxidant activities, ascorbic acid and allicin content, and in vitro antibacterial and anti-proliferative activities. Ultra performance liquid chromatography with diode array detector (UPLC-DAD) was used to detect and quantify gallic acid, chlorogenic acid, caffeic acid, epicatechin, hyperoside, ferulic acid, apigenin, p-coumaric acid and allyl isothiocyanate. All extracts exhibited antioxidant activity with concentrations necessary to inhibit the activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by 50% (EC50) ranging from 60 to 114 mg. Ascorbic acid and allicin ranged between 0.268 and 0.658 mg/g, and between 0.411 and 1.105%, respectively. Extracts exhibited antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa more so than against Bacillus cereus. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays demonstrated that the extracts inhibited the proliferation of the human epithelial colorectal adenocarcinoma (Caco-2) cells in time- and dose-dependent manners.