TRP ACTIVE COMPOUNDS FROM FOOD PLANTS AND THEIR PROPERTIES AS ANTIMICROBIAL AND BIOCIDES

Nowadays plant derived compounds constitute a promising resource in ecofriendly pest and diseases management because they are ‘generally recognized as safe’ (GRAS). Plants have evolved ingenious defense mechanisms by production of pungent and irritant compounds. These substances produce their psychophysical effects by targeting the TRPA1 receptor, belonging to transient receptor potential (TRP) channels. Two secondary metabolites contained in the Asian food plant Perilla frutescens, perillaldehyde (PA) and perillaketone (PK), are potent agonists of TRPA1. The aim of the present PhD project was to determine the antimicrobial activity of the crude extracts and essential oils from the leaves of two Perilla frutescens varieties grown experimentally in Northern Italy. Commercial PA and PK, obtained by chemical synthesis, were also assayed in vitro and in vivo (PA, only). In addition, the nematicidal efficacy of pure PK was evaluated against 2nd instar larvae juveniles of cyst nematode Heterodera daverti. Chemical analysis allowed the identification of PA and PK as the main constituents in the two investigated cultivars respectively, and the consequent classification in PA and PK chemotypes. The organic extracts PA and PK-type (PA-Ex and PK-Ex) and the essential oils PA and PK type (PA-EO and PK-EO) exhibited a broad spectrum of activity against tested phytopatogenic organisms. The antibacterial activity of the tested substances resulted generally scanty. In vitro antifungal activity varied according to compound and target species. The essential oils appeared to be significantly more active compared with the crude extracts. At 500 µg mL-1 PA-EO showed fungicidal activity against several fungi while PK-EO exhibited a fungistatic one. Both oils and commercial PA displayed high inhibition on Cladosporium cladosporoides IPV-F167 spore germination, while PA-Ex and pure PA proved good preventive activity reducing powdery mildew disease on cucumber plants. Besides, P. frutescens demonstrated to possess efficient nematicidal activity due to PK.