Antifungal and biochemical effects of pseudoguaianolide sesquiterpenes isolated from Ambrosia maritima L.

Abstract

Five pseudoguaianolide sesquiterpenes, namely neoambrosin, damsinic acid, damsin, ambrosin and hymenin isolated from the aerial parts of Ambrosia maritima, were tested for their antifungal activity against the most economic plant pathogenic fungi Botrytis cinerea and Fusarium oxysporum which cause grey mold and root rot diseases, respectively. In mycelial radial growth inhibition assay, neoambrosin and damsin were the most potent, while hymenin and damsinic acid were the lowest effective among the tested compounds. F. oxysporum was more sensitive for inhibition than B. cinerea. On the other hand, the sesquiterpenes caused significant reduction in spore germination of both fungi at 50, 100 and 200 mg/L compared with the control. Complete inhibition was observed when the spores treated with damsinic acid and ambrosin at 200 mg/L. In vivo activities of polyphenol oxidase, polygalacturonase and pectin-lyase in both fungi that treated with 0.5 and 1 fold of the EC50 value were also carried out in order to investigate the biochemical influences of the tested compounds. The compounds showed significant inhibitory effects on the enzyme activities compared with the control however; the activity was not consistently related to the in vitro inhibitory effects.