Two new tryptophane metabolites of the American cockroach.

In the course of attempts to isolate and characterize the ‘nesting’ or aggregation pheromone of the American cockroach, Periplaneta americana, two metabolites of tryptophane have been identified. These are oxindole and hydrocarbostyril. That these were indeed tryptophane metabolites was demonstrated by administering radiolabelled tryptophane to cockroaches following tetracycline treatment and isolating the radioactive metabolites. INTRODUCTION LARVAE of the American cockroach, Periplaneta americana, are attracted to hiding places populated by adult cockroaches by the presence of an aggregation pheromone in cockroach excreta (BLOCK and BELL, 1974). To study aspects of the chemical triggering of behaviour patterns, it is of interest to isolate and characterize the pheromone responsible for aggregation. MULLINS and COCHRAN (1973) have examined the excreta of P. americana and find that ammonia, amino mitrogen, unidentified water-soluble products, and some water-insoluble materials and three metabolites of tryptophane are among the nitrogenous wastes produced. We reasoned that the aggregation pheromone might well be in the water-insoluble fraction of the faeces and have examined organic solvent extracts of the excreta for the pheromone. It is in these that two new metabolites of tryptophane are found. MATERIALS AND METHODS A flow chart of the extraction procedure for an active fraction producing aggregation (as determined by bioassay, BLOCK and BELL, 1974) is presented in Fig. 1. The active fraction was further purified by preparative thin-layer chromatography (Silica gel GFss4, Brinkman Instruments Inc., 2 mm) using 15% acetone in methylene chloride as the developing solvent. Visualization of the plates under U.V. light (254 nm), recovery of the adsorbing substances, and bioassay provided an active fraction at Rt O-3 to 0.4. Active fractions from several plates were combined and sublimed (60°C at 1 x 1O-5 Torr). The sublimate was collected (2.5 mg) and subjected to mass spectrometry (Varian-Atlas CH 5, by solid inlet), i.r. spectrometry (Beckman