Garlic (Allium sativum L.) husk waste as a potential source of phenolic compounds: Influence of extracting solvents on its antimicrobial and antioxidant properties

This paper reports the extraction process of polyphenols from the industrially disposed garlic husk (GH) using different studied solvents (water, methanol, ethanol and 50% aqueous solutions of methanol and ethanol). The highest extraction yield was achieved with water (26.5%) and high bioactive potential was shown by the samples extracted with 50/50 methanol/water (25 mg GAEs/g dry GH, 0.617 mg QE/g dry GH, IC50 = 0.26 mg/mL for DPPH assay, RP0.5AU = 2.8 mg/mL for reducing power, and IC50 = 0.45 mg/mL for hydroxyl radical assay). All the extracts exhibited antimicrobial activity against Gram-positive bacteria, when applied at different concentrations (1-10 mg/mL). Only 50/50 methanol/water and absolute methanol extracts inhibited the growth of Pseudomonas aeruginosa and Klebsiella pneumonia. These interesting biological properties could be attributed to the major identified phenolic compounds, such as caffeic, p-coumaric, ferulic and di-ferulic acids. With this procedure, the GH waste polyphenols could be used as a cheap source of natural compounds, with potential applications in the food and health sectors. (C) 2014 Elsevier B.V. All rights reserved.