ABSTRACT
Sweet potato (Ipomoea batatas L.) is a widely grown crop in tropical countries as food and feed, and a good source of energy, minerals and vitamins. It is a source of antioxidative polyphenols such as anthocyanins and phenolic acids. In this study, the concentrations of polyphenols, anthocyanins, and the antibacterial activity of alcoholic extracts, infusion and decoction of leaves of two accessions of sweet potato were evaluated against three agents of interest in food, which are standardized inocula of Salmonella Enteritidis (ATCC 11076), Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 11229), in Porto Alegre, RS. Evaluation of antibacterial activity, expressed as intensity of activity of bacterial inhibition (IINIB) and bacterial inactivation (IINAB), was based on tests of dilution in multiple tube system; anthocyanins were determined by differential pH and polyphenols by Folin & Ciocalteu. The alcoholic extracts inhibited and, or inactivated all inocula tested although Staphylococcus aureus were significantly more resistant. Decoction and infusion extracts, in addition to having very low concentrations of anthocyanins and lower polyphenol contents than their corresponding alcoholic extracts, showed no antibacterial activity. The antibacterial activity of the extracts tested was positively correlated to phenolic compounds and, or anthocyanins.
Key words:
Polyphenols; anthocyanins; bacterial activity; inhibition; inactivation
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