Purpose: In this study, the use of three citrus byproducts, Citrus limon, Citrus aurantium, and Citrus medica, to prevent adherence and invasion of C. jejuni in HeLa cells was evaluated. The effects of these extracts on expression levels of genes involved in adherence and invasion processes (cadF and ciaB) were also examined. Furthermore, were determined the antioxidant activities and the contents of phenolics and flavonoids in these extracts.
Methods: Extracts were added to cultures of C. jejuni and determined the adherence/invasion ratio to HeLa cells. The relative expression of cadF and ciaB, and the housekeeping gene glyA was determined by real time qRT-PCR. Total contents of phenolic and flavonoid compounds, DPPH radical scavenging activity, and the Trolox-equivalent antioxidant capacity of extracts were determined by spectrophotometric methods.
Results: In general, byproduct extracts at subinhibitory concentrations affected adherence (reduced 2.3 to 99%) and invasion (reduced 71.3 to 99.2%) to HeLa cells. The expression of cadF and ciaB, was reduced 66 to 99% and 81 to 99% respectively, depending on strain or extract added. The total phenolic content of byproducts varied from 92 to 26 mg GAE/g, and total flavonoids from 161 to 29.29 mg QE/g. C. aurantium showed the highest % of radical scavenging activity (RSA, 90.1).
Significance: Citrus byproduct extracts could be good alternatives for devising new strategies to control Campylobacter infections.