Antioxidants of Fruit Extracts as Antimicrobial Agents against Pathogenic Bacteria

Abstract

Fruit is an essential part of the human diet and is of great interest because of its richness in phytochemicals. Various fruit extracts from citrus, berries and pomegranates have been shown to possess a broad spectrum of medicinal properties. Fruit phytochemicals are of considerable interest because of their antioxidant properties involving different mechanisms of action, which can act against different pathogenic bacteria. The antioxidant capacity of fruit phytochemicals involves different kinds of reactions, such as radical scavenging and chelation or complexation of metal ions. The interaction between fruit phytochemicals and bacteria has different repercussions: it disrupts the cell envelope, disturbs cell-cell communication and gene regulation, and suppresses metabolic and enzymatic activities. Consequently, fruit phytochemicals can directly inhibit bacterial growth or act indirectly by modulating the expression of virulence factors, both of which reduce microbial pathogenicity. The aim of this review was to report our current knowledge on various fruit extracts and their major bioactive compounds, and determine the effectiveness of organic acids, terpenes, polyphenols, and other types of phenolic compounds with antioxidant properties as a source of antimicrobial agents.

Keywords: antimicrobial activity mechanisms; antioxidant properties; fruit extracts; organic acids; polyphenols; terpenes.

Figure 1

Metal ion complexation from flavonoids. Flavonoids that have ability to chelate metal ions (Fe³⁺, Cu²⁺) at the sites include 3′,4′-dihydroxy group on the B ring (rutin and catechin) and 3-hydroxy and 4-oxo groups on the C ring (galangin and quercetin).