Effect of harvest time on antioxidant activity of Glycyrrhiza glabra root extract and evaluation of its antibacterial activity

Glycyrrhiza glabra roots harvested at two different times (T1: 20 October 2010 and T2: 20 January 2010) were analyzed for their chemical composition, and then antioxidant activity and antibacterial effect of ethanolic root extract against some pathogenic bacteria were evaluated. Higher amounts of moisture were detected in T1 licorice root, whereas higher levels of sugar, protein, ash and phenolic compounds were determined in T2 licorice root. The antioxidant activity was assessed by DPPH, reducing power and total antioxidant capacity assay and T2 licorice root was found to possess higher antioxidant activity. Antimicrobial activity was estimated using a microdilution technique (ELISA) against some human pathogenic bacteria. The following bacteria were tested: Salmonella entritidis (gr^-), Escherichia coli (gr^-), Bacillus cereus (gr^+) and Staphylococcus aureus (gr+). It exhibited antimicrobial activity against both tested Gram-positive and Gram-negative bacteria.