Inhibitory effects of steroidal allenes on growth,development, and steroid metabolism of the silkworm,Bombyx mori

Steroidal allenes, stigmasta-5,24(28),28-trien-3β-ol (allene-I) and cholesta-5,23,24-trien-3β-ol (allene-II), were tested for their inhibitory effects on growth, development, and steroid metabolism in the silkworm, Bombyx mori. The allenic analogue (I) of stigmasta-5,24(28)-dien-3β-ol (2) was found to be a specific inhibitor for the conversion of stigmast-5-en-3β-ol (1) to stigmasta-5, 24(28)-dien-3β-ol (2) and/or stigmasta-5,24(28)-dien-3β-ol (2) to 24,28-epoxy-stigmast-5-en-3β-ol (3) This inhibitor held the larvae in the second instar for more than 20 days without developing to the third instar, when administered alone or with the dietary sterols of stigmast-5-en-3β-ol (1) or stigmasta-5,24(28)-dien-3β-ol (2). The second allene (II) with a similar structure to cholesta-5,24-dien-3β-ol (4) was also found to be an inhibitor for insect growth and development, but it appeared not to be acting via inhibition of sterol dealkylation.