Berberine as a natural compound inhibits the development of brown rot fungus Monilinia fructicola

Abstract

Peach brown rot is a severe disease caused by ascomycete fungus Monilinia fructicola and is primarily controlled by chemical fungicides. However, the utilization of fungicides has caused many problems such as microbial resistance, environmental pollution, and fruit contamination. The growing concern for food safety requires alternative management methods that are safe to humans and benign to the environment. Here we report that the extract from Coptis chinensis (a Chinese herb named “Huang Lian”) demonstrates a strong inhibition to M. fructicola. The 50% effective concentration (EC 50) of C. chinensis extract to M. fructicola was only 0.91 mg/mL, while the EC 50s to other fungi such as Botrytis cinerea and Alternaria solani were 14.09 mg/mL and 27.35 mg/mL, respectively. These results indicate that the extract of C. chinensis has a specific inhibition to M. fructicola. Subsequent partitioning of the ingredients in C. chinensis extract revealed that berberine, the conventional anti-bacterial alkaloid, was the predominant ingredient that exerted robust inhibition against M. fructicola. The EC 50 and minimum inhibitory concentration (MIC) against M. fructicola were as low as 4.5 μg/mL and 46.9 μg/mL, respectively. Compared to berberine’s analogs in C. chinensis such as palmatine, berberine tannate and jatrorrhizine, berberine showed the strongest inhibition against M. fructicola. This finding provided insight into the structure–activity relationship between berberine and its analogs. Notably, not only can berberine prevent spore germination and hyphal growth, it also inhibits the activity of cutinase secreted by M. fructicola, implying the potential function of berberine in reducing the pathogenesis of M. fructicola. In addition, the strong in vivo inhibition of berberine against M. fructicola was observed with no visual cytotoxicity noted to peach fruits, even at berberine concentration of 400 μg/mL. Note that this was much higher than its MIC value (46.90 μg/mL). Overall berberine, as a natural compound, may be a promising candidate in control of brown rot.