Abstract: In this report, a preliminary isolation of AS from the brains of larvae, Mythimna separata, is described. The ASactivity material which can inhibit JH synthesis by CA occurs in the brains of last instar. The ability of brain extract to inhibit JH synthesis in vitro was tested by radiochemical assay. Using 1 brain equivalent, 51% inhibition of JH synthesis was achieved. If the brain extract was pretreated with trypsin, the inhibitory effect of the extract was greatly reduced. Assays of fractions from the reversalphase C18 column of HPLC separation showed that materials with AS activity were eluted between 5.2% to 28% methanol (fraction 1～20), and between 40% to 76% methanol (fraction 30～60). Assays of fractions 3, 5, 11, 40, 54 and 60 using 5 brain equivalents per pair of CA showed >50% inhibition of JH synthesis. Further purification of the fractions from the C18 column with allatostatic activity is in progress.

Key words: Mythimna separata, allatostatin, brain extract, HPLC