Allelopathy of Ageratum conyzoides L. VII. Syntheses of analyogs of ageratochromene and their inhbitory effects on plants and microorganisms

Five analogs of ageratochromene were synthesized and their inhibitory effect on plants and microorganism s were compared with that of ageratochromene. Results showed that two analogs, 6-formy1-7-methoxyl-2, 2-dimethyl-2H-benzopyran and 7-hydroxyl-6-form y1-3, 4-dihydro-2, 2-dimethyl-2H-benzopy-ran had higher inhibitory effects on two plants: radish and ryegrass than that of ageratochromene at concentration of 100mg/1, especially inhibited the root growth of plants significantly. They also possessed stronger antimicrobial activity and the inhibitory rates for two fungi(Rhizoctonia solani and Phytophthora capsici)were 100% at concentration of 400mg/l, m oreover, 7-hydroxyl-6-formly l-3, 4-dihydro-2, 2-dimethyl 2H-benzopyran inhibited two bacteria species significantly: Xanthomonas oryzae pv. oryzae and Erwinia chrysanthemi at concentration of 2000m g/1. Researches revealed that 2, 2-dimethyl-2H-benzopyran, the basic structure of constituting ageratochromene was not correlated with its allelopathic and antimicrobial effecs. However, as there were active substituents at its 6-or 7-position, both effects were strengthen significantly.