Antimicrobial and phytotoxic activities of secondary metabolites from Haplophyllum tuberculatum and Chrysanthemum coronarium

Abstract

Phytochemical investigation led to the isolation of three alkaloids [skimmianine (1), vulcanine (2) and evoxine (3)] from the aerial parts of Haplophyllum tuberculatum, and two diacetylenic spiroketal enol ethers [spiroketalenolether polyyne (4) and [7-hexa-2,4-diynylidene-1,6-dioxaspiro[4.4]nona-2,8-dien-4-yl] acetate (5)] and a sesquiterpene lactone [8α acetoxy-11β,13dihydrokauniolide (6)] from the aerial parts of Chrysanthemum coronarium. The chemical structures of the isolated compounds were determined by using spectral data of 1H NMR, 13C NMR, as well as by comparison with literature data. Compounds 4, 1 and 5 were the most potent inhibitors against plant pathogenic bacteria Rhizobium radiobacter, Ralstonia solanacerum and Pectobacterium carotovorum ss. carotovorum with minimum inhibitory concentration (MIC) values of 31.3, 62.5 and 31.3 µg/ml, respectively. In antifungal assay, compounds 1 (MIC 62.5 µg/ml), 2 (MIC 62.5 µg/ml) and 5 (MIC 125 µg/ml) caused the highest inhibitory effects against phytopathogenic fungi Verticillium dahliae, Fusarium oxysporum and Alternaria solani, respectively. Moreover, crude extract of H. tuberculatum and 4 were significantly the most potent inhibitors of seed germination, root and shoot growth of Echinochloa crus-galli.