Antioxidant Activities Of Rehmannia Glutinosa Extracts

Rehmannia glutinosa is the perennial herbs,belong to scrophulariaceae and Rehmannia. The main medicinal part is its underground parts, namely the root. The version of 2005"China pharmacopoeia"have fresh radix rehmanniae, rehmanniae, Prepared rehmannia root. and the traditional Chinese medical plant Rehmannia Root contains various types of compounds including iridoid glycosides, phenols, polysaccharides, amino acids, organic acids and etc. These compounds endows Rehmannia many pharmacological actions like anti-aging, lowering the blood glucose, Anti-inflammatory effect, as well as improving the functions of the immune system. Therefore, probing into active ingredients in Rehmannia and seeking for their biological functions will provide reliable theoretical and experimental references for multipurpose utilization of Rehmannia resources.In this research, Rehmannia glutinosa is taken as the raw material, the method of reflux extraction with 70% alcohol is employed to extract the antioxidant compounds in Rehmannia glutinosa. Finally, four phases are separated, the Petroleum ether phase, chloroform phase, ethyl acetate phase and butanol phase respectively. We further analyze and determine the extraction rate, the total phenolics and total iridoid glycosides in the four extracts, and conduct pre-test to the antioxidant ingredients in different extracts. We investigate the antioxidant activity of the above mentioned four extracts (BHT as the control) by way of the DPPH method, the Feton method, Potassium dichromate oxidation method, the method of PMS-NADH system generating Superoxide anion and the latter reducing NBT, the FRAP method and Determination of reducing power method (Prussian blue method). And the results are as follows:(1) Also we discover that the compound types in the four different extracts of Rehmannia glutinosa has no significant difference, while the results showed by employing different test methods are different, which may be related to the amount of the ingredients to be test in different extracts. In the four extracts we find the chemicals are phenolic compounds, flavonoids, terpenoids, steroids and triterpenoids.(2) The extraction rates of the four extracts of Rehmannia glutinosa have significant difference,amongst the Butanol extract is the highest, the second is the Petroleum ether extract, and the Ethyl acetate ranks last; the content difference of total phenolics of the four extracts of Rehmannia glutinosa is significant, among which the total phenolics of the Ethyl acetate extract is the highest, then the Butanol extract, the Petroleum ether extract is the lowest; the content difference of total iridoid glycosides of the four extracts of Rehmannia glutinosa is significant,the Butanol extract harbors the most iridoid glycosides, followed by the Chloroform extract, while in the Petroleum ether extract iridoid glycosides is not detected.(3) The results show that all the four extracts of Rehmannia glutinosa have varying degrees of antioxidant activity, and their antioxidant activities and their concentrations have a dose-effect relationship. However, using different evaluation systems of antioxidant capacity, the antioxidant activities of different extracts have significant difference. The ethyl acetate extract exhibits the highest activity in removing DPPH free radicals and the highest reducing capacity as well as the highest total antioxidant capability. Its IC50s are respectively 0.178 mg/mL and 0.341 mg/mL, the FRAP value is 1.215 mM FeSO4/g. furthermore, we discover that the DPPH free radical scavenging capacity of the Ethyl acetate extract is higher than that of BHT(IC50=0.456 mg/mL);the Chloroform extract is the highest in scavenging the Hydroxyl Radicals with IC50 value 1.397 mg/mL; the Butanol extract is high in its capacity of scavenging DPPH free radicals, in its reducing capability and total antioxidant activity, while its abilities of removing Hydroxyl radical and hydrogen peroxide are relatively weak. Amongst the DPPH free radicals scavenging capacity of the Butanol extract is higher than that of the control BHT (IC50=0.456mg/mL); In all tests, the Petroleum ether extract shows very weak antioxidant activity. For we know that the mechanism of antioxidants acting inside the organism is very complex, one substance may exhibit different antioxidant activities in different evaluation systems, so various methods are employed in this assay to conduct an overall evaluation of the antioxidant activity of natural plants and get a reasonable and scientific conclusion.(4) The various methods of determining different antioxidant activities are correlated to a certain extent, and they have some correlations with the total phenol content, among which there is a high correlation between the total phenol content and the total antioxidant activity together with the reducing capacity, Correlation coefficient (R2) respectively 0.9928 and 0.7738; besides, there are important correlations between DPPH free radicals scavenging rate and total antioxidant activity, and reducing capacity , as well as and total phenol content, their Correlation coefficients(R2)respectively 0.7083,0.7738 and 0.6419. Therefore, the Total antioxidant method (FRAP method), the Reducing method (Prussian blue method) and DPPH method are introduced to investigate the different antioxidant activities of Rehmannia glutinosa.