Chemical composition and antioxidant compounds of Rehmannia glutinosa during steaming process

Rehmannia glutinosa(RG) can be used in food or medicine as 3 types; fresh rehmannia root, dried rehmannia root and steamed rehmannia root. This study was performed to compare chemical compositions and antioxidant compounds depending steaming process.

For the study, raw roots of RG were dried, soaked in traditional Korean wine and steamed for 9 times. As a result, the catalpol content of raw root was 26.32mg/g but dramatically decreased after 1^st steaming. It is not detected after 4^th steaming. The content of 5-HMF was not detected at raw roots but started increased from 2^nd steaming. The value exceed 0.1% from 5^th steaming. The contents of two antioxidant compounds including total flavonoids, total polyphenols increased gradually during steaming. Each value was from 0.13mg/g to 0.31mg/g and 0.34mg/g to 0.81mg/g. From the results, we could find that the composition of RG was significantly affected by steaming process. Therefore, suitable process would be helpful for utilizing RG substances in industry.