Prostaglandin synthetase inhibitors in insect defensive secretions

In vitro inhibition of prostaglandin H synthase by compounds from the exocrine secretions of lace bugs

1. Selected lace bug-derived and related compounds were shown to be in vitro inhibitors of mammalian and insect derived prostaglandin H synthase. 2. Two compounds, 2,6-dihydroxyacetophenone and 2,4,6-trihydroxyacetophenone, were significantly better inhibitors of prostaglandin synthesis than aspirin, whereas 2-nonyl-5,7-dihydroxychromone and 1-(2,6-dihydroxyphenyl) dodecan-1-one were equivalent to aspirin. 3. 2,4-Dihydroxyacetophenone was less effective in inhibiting the prostaglandin H synthase and 2-nonyl-5-hydroxychromanone showed no inhibition. 4. Three compounds, 2,6-dihydroxyacetophenone, 2,4,6-trihydroxyacetophenone and 1-(2,6-dihydroxyphenyl) dodecan-1-one were equal to aspirin in PSI inhibition with fat body preparations of the American cockroach Periplaneta americana L.

De novo biosynthesis of polyunsaturated fatty acids in the cockroach Periplaneta americana

The de novo biosynthesis of 6,9,12-linolenic acid, 11,14-eicosadienoic acid, 5,11,14-eicosatrienoic acid, and arachidonic acid was demonstrated in adult female cockroaches, Periplaneta americana. These four polyunsaturated fatty acids (PUFA) were present primarily in the phospholipid (PL) fraction of both males and females. They were purified by AgNO3 thin-layer chromatography and high pressure liquid chromatography. The double bond positions of the major isomer of eicosatrienoic acid were shown to be at the delta 5,11,14 positions by gas chromatography-mass spectrometry (GC-MS) of both methoxy and epoxide derivatives and gas-liquid chromatography (GLC) and GC-MS of ozonolysis products. The other PUFAs cochromatographed with standards on both packed and capillary GLC columns. The in vivo incorporation of [1-14C]acetate into 5,11,14-eicosatrienoic acid, 11,14-eicosadienoic acid, 6,9,12-linolenic acid, and arachidonic acid was demonstrated by radio-GLC and radio-HPLC and for 5,11,14-eicosatrienoic acid by radio-GLC of ozonolysis products. The latter technique clearly demonstrated that the entire eicosatrienoic acid molecule was labeled. Thoracic tissue contained the highest amount of radiolabeled 5,11,14-eicosatrienoic acid (1.6% of total radioactivity incorporated into PL) while radiolabeled 11,14-eicosadienoic acid was found primarily in abdominal epidermal tissue (2% of total radioactivity incorporated into PL). Radiolabeled arachidonic and 6,9,12-linolenic acids comprised 0.1 and 0.02%, respectively, of the total radioactivity in the PL fraction. These data document the de novo biosynthesis of di-, tri-, and tetraunsaturated fatty acids in the American cockroach, and indicate that this animal can desaturate on both sides of the delta 9 double bond of oleic acid.