Mioganal, a novel pungent principle in myoga (Zingiber mioga Roscoe) and a quantitative evaluation of its pungency.

We isolated a novel pungent principle from the flower buds of myoga. Based on an interpretation of the HR-MS, EI-MS, IR, UV, and NMR data, this compound was (8betaH)-14,17-cyclolabda-12,14(17)-diene-15,16-dial (mioganal, 1). We determined the threshold value of mioganal to be 5.6x10(-5) g/ml, which is about eight times greater than that of 8beta(17)-epoxy-12(E)labdene-15,16-dial (miogadial), the main pungent principle in the flower buds of myoga. In addition, we examined the content of mioganal in different parts of different varieties. Mioganal is mainly distributed in the leaves of both natsumyoga and akimyoga varieties at 1.60 mg/100 g fresh weight on average, its amount being three times higher than that in the flower buds.