Sunflower husks: an agroindustrial byproduct enriched in phenolic compounds with antifungal properties

MARTÍNEZ, GUADALUPE; REGENTE, MARIANA; DEL RÍO, MARIANELA; PINEDO, MARCELA; DE LA CANAL, LAURA

Virtual

Congreso; XXXIII Argentinian Meeting of Plant Physiology; 2021

Sociedad Argentina de Fisiología Vegetal

Plants synthesize diverse types of secondary metabolites, including phenolic acids, terpenes, flavonoids, essential oils and alkaloids, which are involved in protection against fungal infections. Sunflower husks, an under-appreciated byproduct of the oil industry, are enriched in phenolic compounds. The aim of this work was to explore the antifungal potential of sunflower husk ethanolic extracts against different pathogenic fungi of agronomic importance and provide insights on its mechanism of action. Phenolic extracts of sunflower husks (EPC) were prepared by maceration in 80% ethanol. The composition analysis by RP-HPLC showed that the main phenolic compound in the extract was chlorogenic acid. In order to assess the antifungal activity, fungal spores were incubated with increasing doses of EPC and subjected to microscopic observation. EPC 0.4 mg/ml inhibited spore germination of Sclerotinia sclerotiorum, Fusarium solani, Fusarium oxysporum and Verticillium dalhiae. Further analysis of cell viability by Evans Blue staining revealed the permeabilization of the plasma membrane, suggesting the cytotoxic action of EPC. The fungicidal effect was confirmed by treatment with EPC and subsequent culture on media potato dextrose agar. In addition, using diaminobenzidine to detect reactive oxygen species, EPC-treated spores showed increased endogenous peroxides production. Our findings indicate that EPC displayed antifungal activity on different phytopathogenic fungi through cytotoxic effects mediated by oxidative stress and cell permeabilization. The bioactive properties of EPC contribute to valorize a byproduct of the oil industry that is usually discarded