AbstractsChemistry

In 1959 Kitagawa discovered and isolated the amino acid, canavanine. Since its discovery much interest has been centered on this amino acid because of its biological aspects; e.g. canavanine has been shown to inhibit the growth of bacteria, viruses, protozoa, and cancer cells. The occurrence of canavanine is widespread in the leguminous plants and its identification and isolation for this reason has been restricted to these plants; of the leguminous plants, jack bean meal (Canavalia ensiformis) has been a readily available source. The most notable of its properties is the characteristic ruby red color which canavanine forms with sodium nitroprusside. This color formation has been used for the identification of canavanine in natural products. An unfortunate reaction of canavanine is its deamination and cyclization to desaminocanavanine under neutral conditions. This conversion has been responsible for some of the loss of canavanine during its isolation. A, useful reaction which canavanine undergoes is the formation of an insoluble salt with flavianic acid. The formation of canavanine diflavianate is the usual method for the isolation of canavanine from crude extraction mixtures. However, various workers have experienced difficulty in the conversion of canavanine diflavianate to its free base and thus they have introduced various modifications in the procedure. The author in attempting to isolate canavanine from the crude extracts by the use of flavianic acid has also found the conversion of canavanine diflavianate to its free base (canavanine) difficult and tedious. It was found that in order to effect a complete conversion, a large excess of barium hydroxide must be added to an incipient boiling solution of canavanine diflavianate. Under these conditions a reliable isolation of canavanine was obtained. Since the use of flavianic acid in the isolation of canavanine has proved to be difficult and tedious an ion exchange method which avoids the use of flavianic acid has been investigated. The results with this method indicated that a quantitative and practical isolation of canavanine directly from the crude extracts could be achieved. The use of a strongly acidic ion exchange resin in conjunction with a preferential eluting agent has been the key for the separation and isolation of canavanine as its free base from the impurities in the crude extract.