The chemistry and allelopathic effects of phenolic compounds from the Lichen Evernia prunastri (L.) Ach.

Abstract

Fifteen biogenetically-re!ated phenolic substances were obtained from the lichen Evernia prunastri: orsellinic acid, evemuuc acid, methyl everninate, ethyl eveminate, methyl di-0-methylorsellinate, evemic acíd, methyl 2'-0-methyl lecanorate, methyl 􀃨-orsellinate, methyl hematomate, ethyl hematomate, evernin, atranorin, 2,2'--di-O-methylgyrophoric aoid, prunastrin, and (+)-usnic acid. Seven were found for the first time in this species and three (methyl 2'-0-methyl lecanorate, 2,2'-di-O-methylgyrophoric acid and prunastrin) have never been reported before. New physicochemical data were recorded for all compounds. Chemical/HPLC chromatographic correlation detected the two monocyclic fragments of evemic acid, the unstable orsellinic and everninic acids in the acetone extract of the lichen. A mixture of ali the phenolic substances from E. Prunastri, k.noV1on as "Evernal", was applied to cabbage, green pepper and tomate seedlings, at both steady and allernant (nighUday) temperatures and it was observed that although some seeds were more resistant than others, a 2.0% concentration of the phenolic fraction totally inhibited seed germination at 20 'C, while germination with less than 2% concentrations produced a sickly crop which withered after a few days. LD50 (in % w/w evemal) were 0.31 for cabbage, 0.37 for tomato and 1.80 for peppers. Sharp, regular drops in temperature increased the allelopathi􀏉 activ