Pavietin, a coumarin from Aesculus pavia with antifungal activity

A new prenylated coumarin, S-6-[2-(hydroxymethyl)butoxyl-7-hydroxy-4-methyl-2H-chromen-2-one (1), named pavietin, has been isolated from the leaves of an Aesculus pavia genotype along with three known flavonol glycosides, quercetin 3-O-alpha-rhamnoside (quercitrin, 2), quercetin 3-O-alpha-arabinoside (3), and isorhamnetin 3-O-alpha-arabinoside (distichin, 4). The chemical structure of compound 1 was determined by chemical and spectroscopic methods, inclusive of UV, MS, and ID and 2D NMR experiments. It showed appreciable antimicrobial properties against several pathogens, displaying a significant antifungal activity toward one of the main fungal parasites of Aesculus species, Guignardia aesculi. The same biological tests performed with a mixture of flavonoids 2-4 resulted in weak or no activity. Compound 1 was undetectable in Aesculus hippocastanum, a closely related species lacking resistance to fungal pathogens. The possible role of 1 in plant resistance is discussed.