|Budget Amount *help
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥2,800,000 (Direct Cost: ¥2,800,000)
Gastrulation is one of the fundamental events in embryogenesis, and is the first process closely related to cellular differentiation. During our search for inhibitors of starfish (A sterina pectinifera) embryonic development, we found that the n-BuOH extract of a new actinomycete species belonging to the genus Micromonospora inhibited gastrulation of A. pectinifera embryos. Bioassay-guided chromatographic fractionation led to the isolation of new bioactive macrolides designated micromonospolides A (1), B (2) and C (3). Spectroscopic data showed that micromonospolides A(1), B(2) and C (3) contain a 16-membered lactone ring as that of bafilomycins. When 8-hours-old embryos at the early blastula stage of A. pectinifeta were cultured in the presence of 1-3, the progression of embryonic development was arrested at the late blastula stage just prior to gastrulation at minimum inhibitory concentrations of 0.010, 0.011 and 1.6 μg/mL, respectively. Micromonospolide B (2) showed nearly the same inhibitory activity as that of 1, indicating that the presence of an N-(3-hydroxy-2-cyclopentenone-2-yl)-fumarylester monoamide functionality at C-21 in 1 does not affect the activity. Micromonospolide C (3) was 100-fold less active than 1 or 2, indicating that the opening of the tetrahydropyran ring (C-19 to C-23) and the subsequent formation of the α,β-unsaturated ketone functionality resulted in the decrease in potency of the inhibitory activity. On the other hand, the minimum inhibitory concentration of bafilomycin A_1, which has an isopropyl group attached to a tetrahydropyran ring, was 0.10 μg/mL corresponding to one-tenth of the activity of 1. The potent inhibitory activity of 1 and 2 against gastrulation of the starfish embryo seems to be due to the replacement of the isopropyl group in bafilomycin A_1 by the (E, E)-1, 3-pentadienyl group.