Antioxidant and antimicrobial activities, and HPLC-PDA-ESI-MS profile of phenolic extract of Urtica dioica L.

Abstract

Stinging nettle (Urtica dioica) is a perennial herb that has been used for centuries as a remedy and food ingredient. This study aims to investigate the polyphenolic profile of an extract of U. dioica and to evaluate its antioxidant and antimicrobial activity. The total polyphenol content of the extract was determined to be 8.065 mg gallic acid equivalent (± 0.0125), while flavonoids were determined to be 3.93 mg quercetin equivalent (± 0.056) and hy-droxynnamic acids were determined to be 2.159 mg caffeic acid equivalent (± 0.01). Nine flavonoids and seven hydroxycinnamic acids and their derivatives were identified by HPLC-PDA ESI/MS, rutin and ferrulic acid were the most abundant with respectively 2005 and 215 μg/g of fresh nettle. The extract showed significant anti-free radical and antioxidant activity in correlation with its polyphenol content. For the antimicrobial tests evaluated against Gram-positive and Gram-negative bacteria, the polyphenols of U. dioica had an effect on most strains tested, the most sensitive of which were S. aureus and C. albicans. The results obtained confirm the bioactive potentials of nettle polyphenols and their possible food and pharmaceutical applications.