COMPARATIVE-STUDY OF PROTEINASE-INHIBITORS IN TROPICAL ROOT CROPS AND SURVEY OF ALLELOCHEMICALS IN THE EDIBLE AROIDS

A comparative study was made of the amount of proteinase inhibitors present in tropical root crops. In Alocasia macrorrhiza, the amount of trypsin inhibitor exceeds that reported elsewhere in potato, barley, and legumes and is 10-100 times greater than the amount present in sweet potato and taro (Co-locasia esculenta). The latter amounts to 1-10 times that found in Cyrtosperma chamissonis. No significant amounts of trypsin inhibitor are present in cassava, yam (Dioscorea spp.), and taro (Xanthosoma sagittifolium). The trypsin inhibitor molecule found in A. macrorrhiza is also a chymo-trypsin inhibitor. Chymotrypsin inhibitor is absent from the other tropical root crops studied. For A. macrorrhiza and C. chamissonis there is a correlation between crude protein and trypsin inhibitor contents. Such a correlation is lacking for taro Colocasia and sweet potato, which unlike A. macrorrhiza and C. chamissonis have been subject to extensive selection/breeding. The content of allelochemicals (trypsin inhibitor, calcium oxalate raphides and acridity) present in five edible aroids is generally consistent with the “apparency” (defined as the susceptibility to discovery by parasites) of the plant part and its resistance to parasites in the South Pacific, except for taro Xanthosoma (relatively recently introduced to the region) which is more resistant to parasites than expected. © 1990, American Chemical Society. All rights reserved.