Protein metabolism in the fifth instar of Bombyx mori L. mediated by a juvenile hormone analogue isolated from Bemchi (Psoralea corylifolia L.)

A juvenile hormone analogue, bakuchiol extracted from the medicinal herb, Bemchi (Psoralea corylifolia) was administered to the 5^th instars of a bivoltine silkworm hybrid, KA x NB₄D₂ to study its influence on the protein metabolism of silkworm larvae preparing to cocoon spinning. The extract was made up to a concentration of 1.25 ppm and administered to the larvae at a dose of 12.5 ml/100 larvae at 24, 48, 72 and 96 h of 5^th instar. This was the concentration of the extract proved to enhance silk production. Posterior silk gland (PSG), haemolymph and fat body were collected from fully-grown larvae and analyzed for the content of total protein and total free amino acid following standard procedures. The activities of transaminase enzymes, glutamic oxalacetic acid transaminse (GOT) and glutamic pyruvic transaminase (GPT) were also determined. The result indicated that the content of total protein and free amino acids increased significantly in the selected tissues depending on the time of JHA application. The highest content of protein in the haemolymph and silk gland was in the larvae treated at 72 h whereas the fat body protein content was the lowest in the same group. The total free amino acid was found to be the highest in 72 h treated larvae in all the tissues. GOT activity in haemolymph and fat body was the highest in 72 h treated larvae whereas in PSG, it was the highest in the larvae treated at 24 h. GPT activity in the haemolymph and silk gland was maximum in the larvae treated at 24 h and in fat body it was in the larvae treated at 72 h. The results indicate that the JHA induces tissue specific responses in terms of protein metabolism.