Mentha aquatica extract: total phenols and flavonoids content, radical scavenging potential and its antibacterial activity on a number of Gram-positive and Gram-negative bacteria “in vitro”

This study investigated the total phenols and flavonoids content, antioxidant potential (based on DPPH and ABTS free radical scavenging methods), and antibacterial mechanism (based on disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum bactericidal concentration) of ethanolic extract of Mentha aquatica. The extract contained significant levels of bioactive phenolic compounds (total phenol: 88.47 ± 0.32 mg gallic acid per gram of extract; total flavonoids: 39.15 ± 0.25 mg quercetin per gram of extract) with acceptable ability in scavenging DPPH (58.50 ± 0.57%) and ABTS (51.44 ± 0.32%) free radicals. The growth of pathogenic and spoilage bacteria, especially Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) in comparison with Gram-negative pairs (Escherichia coli and Salmonella enteritidis) was strongly inhibited by the plant extract. In general, Staphylococcus aureus and Salmonella enteritidis were the most sensitive and resistant microbial strains to the ethanolic extract of M. aquatica, respectively. The present study showed that the ethanolic extract of M. aquatica with significant antioxidant and antimicrobial properties can be used to develop new natural preservatives for food and medicinal purposes.