Ecofriendly synthesis of halogenated flavonoids and evaluation of their antifungal activity

Brominated and chlorinated flavonoids belonging to different classes (flavanones, flavones and catechins) were prepared from the corresponding flavonoids by a simple and ecofriendly procedure based on the use of sodium halides, aqueous hydrogen peroxide and acetic acid. Pure samples of substrates and products were tested against Trichoderma koningii, Fusarium oxysporum and Cladosporium cladosporioides, common saprotrophic soil and seed fungi, potential pathogens for humans and their activity was expressed as linear mycelial growth inhibition (%). Among them, 8-chloro-5,7,3′,4′-tetramethoxyepicatechin 29, a novel catechin derivative, exhibited a remarkable effect against all tested fungi also at low concentrations.