Chemistry

The tetrapyrrolic chlorophyll catabolites (or phyllobilins, PBs) were analyzed in yellow fall leaves of the grape Chardonnay, a common Vitis vinifera white wine cultivar. The major fractions in leaf extracts of V. vinifera, tentatively assigned to PBs, were isolated and their structures elucidated. The dominant fraction is a dioxobilin-type non-fluorescent Chl-catabolite of a previously observed type. Two less polar fluorescent PBs were characterized as a novel dioxobilin-type fluorescent Chl-catabolite with a bicyclo-1',6'-glycosyl architecture, and its new fluorescent formyloxobilin-type analogue. The discovery of persistent hypermodified fluorescent PBs with the architecture of bicyclo-[17.3.1]-PBs (bcPBs), suggests the activity of an unknown enzyme that forges the 20-membered macroring at the tetrapyrrolic core of a fluorescent PB. bcPBs may play specific physiological roles in grapevine plants and represent endogenous anti-infective agents, as found similarly for other organic bicyclo-[n.3.1]-1',6'-glycosyl derivatives