Impact of polyphenolic extracts on resistance to fungal contamination in dry bean grains

Abstract

From their significant roles against the biotic and abiotic stresses, polyphenols have aroused a growing interest for a possible application in food industry. The aim of this study was the evaluation of antifungal activity of polyphenols extracted from two varieties of dry bean, presenting white (Tima) and red (MGT djedida) color. Determination of moisture for the two varieties showed that these grains are favorable for moulds growth. Purification and microscopic study of the isolated strains from beans allowed the identification of six moulds genera: Alternaria, Aspergillus, Moniliella, Fusarium, Penicillium and Rhizopus. Extraction of total polyphenols was carried by a polar solvent and their quantification was based on the reaction of Folin Ciocalteu. The total polyphenolic content was 0.40 ± 0.005 mg EAG/g for the red variety and 0.27 ± 0.005 mg EAG/g for the white variety. The antifungal activity carried by the methods of direct contact, dilution, and antifungal index (IA₁₀₀) demonstrated the antifungal capacity of polyphenols; most sensitive strains isolated are Alternaria sp., Moniliella sp. and Rhizopus sp.. The most active polyphenols are polyphenols extracted from presumably healthy red grains. Our results lend support of the creation of varieties bean high in polyphenols, which act as natural preservatives and bio-effective agents, and offer an alternative to chemical agents for protection of harvested beans in storage structures.

Keywords: Polyphenols, antifungal activity, dry bean

African Journal of Biotechnology Vol. 12(20), pp. 2978-2985