The nature of the taro acridity factor

Abstract The acridity in Araceae species was not apparently due to the calcium oxalate raphides. Some irritant on the raphide surface caused the acridity, with the raphides apparently functioning to carry the acridity factor. Methanol and methylene chloride extracts from purified raphides did not show any compounds in GC-mass spectrometry (MS) analysis that could be regarded as acrid. The data suggested that a 26 kDa protein, possibly a cysteine proteinase, was the active factor. There were a few other uncharacterized protein bands associated with the raphides that could also be involved. Some amino acid sequence data for the 26 kDa protein was obtained.