In China, rhubarb is processed by several methods to enhance particular desirable effects and reduce side effects. One of the resultant products is known as 'Jyuku-daiou' (JD) in Japanese (Shu-dahuang in Chinese). In ancient times, there were two methods for preparing JD, steaming and steaming after processing with liquor (liquor-steaming). At present, JD refers to liquor-steamed rhubarb; therefore, the medicinal effect of JD may have changed. In this report, we elucidated the medicinal effects of steamed (St) rhubarb and liquor-steamed rhubarb by searching the Chinese medical literature from ancient times. Next, we compared the contents of the principal compounds in St rhubarb and two types of liquor-steamed rhubarb, rhubarb sprayed with 16% ethanol (as a substitute for huangjiu) before being steamed (LSp + St) and rhubarb soaked in 16% ethanol before being steamed (LSo + St).
In herbological study, we found that JD was used as a remedy for poison, improving blood stasis, and moistening the bowel in ancient times. Furthermore, in chemical study, we found that St and LSp + St had decreased sennoside contents, while LSo + St had an increased anthraquinone content and a decreased sennoside content. Therefore, LSo + St is the only process that increases the contents of anthraquinones, which have anti-bacterial and anti-inflammatory effects that have been linked to detoxification effect, and we think that all processed rhubarbs may have relatively strong blood stasis improving effects due to their decreased sennoside contents. However, we could not confirm that processed rhubarb moistens the bowel.