UVA Photoactivation of Harmol Enhances Its Antifungal Activity against the Phytopathogens Penicillium digitatumandBotrytis cinerea

GABRIELA M. OLMEDO; LUCIANA CERIONI; MICAELA M. GONZÁLEZ; FRANCO M. CABRERIZO; SABRINA I. VOLENTINI; VIVIANA A. RAPISARDA

Frontiers in Microbiology

Frontiers Media

Año: 2017 vol. 8

Phytopathogenic fungi responsible for post-harvest diseases on fruit and vegetablescause important economic losses. We have previously reported that harmol (1-methyl-9H-pyrido[3,4-b]indol-7-ol) is active against the causal agents of green and gray moldsPenicillium digitatumandBotrytis cinerea, respectively. Here, antifungal activity of harmolwas characterized in terms of pH dependency and conidial targets; also photodynamiceffects of UVA irradiation on the antimicrobial action were evaluated. Harmol wasable to inhibit the growth of both post-harvest fungal disease agents only in acidicconditions (pH 5), when it was found in its protonated form. Conidia treated with harmolexhibited membrane integrity loss, cell wall disruption, and cytoplasm disorganization.All these deleterious effects were more evident for B. cinereain comparison toP. digitatum. When conidial suspensions were irradiated with UVA in the presenceof harmol, antimicrobial activity against both pathogens was enhanced, compared tonon-irradiated conditions.B. cinereaexhibited a high intracellular production of reactiveoxygen species (ROS) when was incubated with harmol in irradiated and non-irradiatedtreatments. P. digitatumshowed a significant increase in ROS accumulation only whentreated with photoexcited harmol. The present work contributes to unravel the antifungalactivity of harmol and its photoexcited counterpart against phytopathogenic conidia,focusing on ROS accumulation which could account for damage on different cellulartargets.