Quantitative analysis of allantoin in fresh tubers of Dioscorea opposita 'Tsukuneimo'

Allantoin in fresh tuber of Dioscorea opposita 'Tsukuneimo' was quantitatively analyzed because the compound is thought to prevent inflammation and ulcers in humans as well as to play an important role for storage and translocation of nitrogen in higher plants. The content of ureide (allantoin and allantoic acid) in 'Tsukuneimo' was determined by the modified method of spectrophotometry with phenylhydrazine, whereas the content of allantoin was determined by HPLC. Analyses revealed that 'Tsukuneimo' tubers contained 2.6 mg·gFW^-1 of allantoin, but leaves or stems had undetectable levels. D. opposita, 'Yamatoimo' and 'Nagaimo', and D. japonica 'Jinenjo' contained 2.3, 0.47 and 1.2 mg·gFW^-1 of allantoin in the tuber, respectively, but negligible amount of allantoic acid in the tuber. Furthermore, Ipomoea batatas and Solanum tuberosum contained less than 0.1 mg·gFW^-1 of allantoin and a negligible amount of allantoic acid. Colocasia antiquorum, 'Ishikawawase' and 'Kyouimo' had no detectable amounts of allantoin or allantoic acid.