Characterization of grape marc hydrolysates and their antifungal effect against phytopathogenic fungi of agricultural importance

Abstract

Winemaking waste contain a high number of bioactive compounds with antimicrobial properties that can be exploited in agriculture. In the present study, hydrolysates from three wine grape (Vitis vinifera L.) marcs were characterized and their antifungal activities against phytopathogenic fungi (Fusarium oxysporum and Alternaria spp.) were evaluated. Wine grape marcs (red, pink and white wine) collected from Ensenada, Baja California, Mexico, were subjected to an acid hydrolysis treatment. Skin hydrolysates of pink and white marcs obtained high concentrations of reducing sugars (5.8 ± 0.1 and 5.5 ± 0.2 g L-1, respectively). Meanwhile, the highest concentration of total sugars was obtained for skin hydrolysates of white marc (9.7 ± 0.08 g L-1). The seed hydrolysates of white marc obtained high concentrations of phenolic compounds (0.52 ± 0.1 mg mL-1). In addition, the highest antioxidant activity was found for skin hydrolysates of red marc (96 ± 0.61%). Results of in vitro antifungal assays clearly indicated a marked inhibition of the mycelial growth and spore viability of F. oxysporum (100% inhibition using red and white hydrolysates) rather than Alternaria spp. (58% inhibition exposed to pink hydrolysates), due to high concentration of phenols. According to HPLC analysis, phenolic acids such as gallic acid, hydroxybenzoic acid, vanillic acid and p-coumaric acid were predominant in the hydrolysates. This study demonstrated that the grape marc hydrolysates exhibit a potential antifungal activity, and highlights that the hydrolysates can be exploited in agriculture as a safe alternative of antifungal agents.