Effects of quercetin and its seven derivatives on the growth of Arabidopsis thaliana and Neurospora crassa

Structure–activity-relationships of quercetin and its seven derivatives were investigated using a shoot growth test with Arabidopsis thaliana seedlings and conidial germination test with Neurospora crassa. All the tested substances inhibited the shoot growth of A. thaliana. On the other hand, in conidial germination test of N. crassa, some flavonoids did not show any inhibitory activity. Quercetin 3-methyl ether and its glycosides especially showed the highest inhibitory effect among them in the conidial germination test of Neurospora. These results indicate that the presence of methyl group in flavonoid nucleus have some important roles as inhibiting effect to A. thaliana and N. crassa.