Structure-Activity Study of Griseofulvin and Its Derivatives for the in vitro Inhibition of Microtubule Polymerization and the in vitro Depolymerization of Microtubule

Abstract

The seventeen derivatives of (+)-griseofulvin [1] were prepared in order to determine the activity of inhibition of microtubule polymerization and the depolymerization activity of microtubule. [1] was chemically transformed to afford its eleven derivatives: [5] [6], and [10] to [18]. Three 6-alkoxy derivatives: [7], [8] and [9] were prepared by the al kylation of 6-demethylgriseofulvin, which was obtained as a metabolite in the urine of rabbits following the administration of [1]. [2] was obtained from the broth of Penicillium urticae fermentation in the presence of potassium bromide. [3] and [4] were prepared from [2] by bromination. The partially purified microtubule proteins from pig brain were used for viscometric analyses. The activities of the test samples were shown as the percentage for the activity of [1], which was expressed as the decreasing ratio of the specific viscosity as cornpared with that of the control, in both experiments (Fig.3 and -Fig-.7). The correlation between the structure and activity was proved and the order of the activities was almost same in both experimental systems, except for isogriseofulvin [11] (Table 1). (-)-Gris'eofulvin [10], the enantiomer of natural (+)-griseofulvin [1], showed the very low activities in both the inhibition of microtubule polymerization and the depolymerization of microtubute. The activities of [1] were also confirmed by electron microscopy, in which samples, were negatively stained with uranyl acetate (Fig.4). Of eighteen samples tested, 3'-bromogriseofulvin [5] showed the highest activities. Accordingly, the aggregate-formation activity of [5] was compared with that of [1] whose activities are thoroughly examined. It was proved that [5] has weaker activity than that of [1] in the formation of aggregate of microtubule proteins at 4°C (Fig.8 and 9).