Effect Of Yeast Fermentation On The Biological Activity Of Steamed Rehmannia Root

Steamed Rehmannia root(SRR)is derived frome dried Rehmannia root by steam processing for several days,thus an antipyretic and blood-cooling herbal medicine becomes a tonic one.Previous studies showed that Maillard reaction took place and a large amount of reducing sugar and 5-hydroxymethyl furfural(5-HMF)generated during the processing.Both small molecular sugars and 5-HMF in SRR were decomposed by yeast,and yeast-fermented SRR(FSRR)was better than SRR in the prevention of the complications of type I diabetes in rats.The results indicate that 5-HMF and small molecular sugars may not be the major effective components of SRR,however it was reported that 5-HMF and Rehmannia glutinosa oligosaccharides have many biological activities in literatures.More researches are needed to clarify whether 5-HMF and small molecular sugars are active components or not in SRR.Based on our previous works,the biological activities of FSRR were further evaluated in this study compared with SRR and 5-HMF as follows:(1)Effect of SRR,FSRR and 5-HMF on acute liver and kidney injuries induced by methotrexate in rats.The results show that both SRR and FSRR could significantly down-regulate the contents of serum aspartate aminotransferase,blood urea nitrogen,urinary glucose and N-acetyl-β-D-glucosidase(NAG),while 5-HMF had little effect except for urinary NAG.(2)Effect of long term feeding of SRR,FSRR or 5-HMF-supplemented food on normal rats.Excretion of calcium,magnesium and sodium by urine is found increased by SRR supplementation,and the amount of feces and fecal nitrogen content also increased,while FSRR and 5-HMF have little influence.(3)The interaction between 5-HMF and human serum albumin.Different concentrations of 5-HMF is incubated with human serum albumin for different times,the result of fluorescent spectrometry reveal that the number of binding sites of 5-HMF on albumin is about 1,however the residual 5-HMF determined by HPLC decreased with time,the curve looks like anti-S shape.In addition,the result of mass spectrometric detection show that their binding belonged to a noncovalent nature.In conclusion,the results indicate that 5-HMF and small molecular sugars might not be the major effective components of SRR.Small molecular sugars may be relate to diarrhea caused by SRR,and 5-HMF might affect the biological functions of albumin.The results of this study support the application of FSRR.