Antibacterial and biochemical activity of pseudoguaianolide sesquiterpenes isolated from Ambrosia maritima against plant pathogenic bacteria

Abstract

Five pseudoguaianolide sesquiterpenes (neoambrosin, damsinic acid, damsin, ambrosin, and hymenin) isolated from the aerial parts of Ambrosia maritima were tested for their antibacterial activity against two plant pathogenic bacteria, Agrobacterium tumefaciens and Erwinia carotovora. The tested compounds exhibited variable degree of antibacterial activity against both tested bacteria as minimum inhibitory concentrations (MIC) ranged 90–520 mg/l. Neoambrosin showed the highest antibacterial activity among the tested sesquiterpenes with MIC values of 150 and 90 mg/l against A. tumefaciens and E. carotovora, respectively. On the contrary, hymenin was the least effective compound with MIC values of 520 and 310 mg/l against A. tumefaciens and E. carotovora, respectively. Neoambrosin, damsinic acid, and damsin caused significant reduction in sulfhydryl group content with the former being the most effective. The tested sesquiterpenes significantly inhibited polygalacturonase and pectin-lyase activities of A. tumefaciens and E. carotovora except for hymenin which caused a significant activation of E. carotovora enzymes.