Synergistic Antioxidant Mechanism Of Huangqi Baizhu Herb Pair

As an important material of functional food, the Chinese therapeutic herbs have been used thousands of years in China to improve the healthy of people. Chinese therapeutic herbs widely used in functional food in the form of formula, and many of them are demonstrated significantly better pharma- cological effects when used in the combination than when used alone. Tradi- tional Chinese herb pairs (TCHPs), which are the basic units in traditional Chinese prescriptions, consist of two relatively standard herbs. Unique com- binations of those herb pairs are frequently used to achieve mutual enhance- ment, assistance, restraint, suppression or antagonism.The Huangqi (Astragalus membranaceus (Fisch.) Bge. var. mongholi- cus (Bge.) Hsiao)-Baizhu (Rhizoma Atractylodis Macrocephalae) herb pair is one of the most widely used herb pairs and has appeared in many tradi- tional Chinese medicine formulas (TCMF), including Qizhutang and Bu zhongyiqitang. This herb pair has been widely used in China to improve diabetic nephropathy and liver cirrhosis. In this paper, changes in the chemi- cal components, antioxidant and antimicrobial activities were detected in the essential oil and ethanol extracts of Huangqi when combined with Baizhu.The antioxidant assays suggested that a synergistic antioxidant effect was observed in ethanol extracts. The components identification of herb pair ethanol extracts were used HPLC-DAD-MS/MS technique. And the results suggested that there are 31 components in herb pair ethanol extracts and 16 of them were identified. A high-performance liquid chromatography 1,1-Di phenyl-2-picrylhydrazyl method (HPLC-DPPH) coupled with an on-line HPLC, diode-array detection and mass spectrometry technique (HPLC-DAD -MS/MS) were successfully used to identify the potential antioxidant compo- nents in Huangqi-Baizhu herb pair extracts. The results indicated there were 11 potential antioxidant components in Huangqi-Baizhu herb pair extracts, 8 of them were identified by their UVλmax, MS, and/or MS/MS dates: Ononin, 9,10-dimethoxy-pterocarpan-3-O-β-D-glycoside, Claycosin, 3'-hyd roxy-5'-methoxyisoflavone-7-O-β-D-glueopyranoside, Formononetin, Atrac- tylenolideⅡ, Atractylenolide VI and Daucosterol. The relative concen tration ratio (CR) analysis suggested that the relative CR of Ononin and Claycosin significant reduced (P<0.05), however, the relative CR of component 6, Formononetin, and Atractylenolide VI significant increased (P<0.05) when Huangqi and Baizhu paired. Quantitative determination of Formononetin and Ononin suggested that the concentration of Formononetin significant increased, mean while Ononin significant reduced (P<0.05) when Huangqi and Baizhu combined. The concentration of those potential antioxi- dant components changed, which may be one reason why the antioxidant activity increased when Huangqi and Baizhu combined. In addition, the hyd- roxyllation reaction may happen when Huangqi and Baizhu combined, which may be another reason.The antioxidant (DPPH and ABTS·~+ radicals scavenging analysis) and antimicrobial activity (growth inhibition of Escherichia coli (E. coli), Micro- coccus luteus (M. luteus), Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), Candida albicans (C. albicans), Aspergillus niger (A. niger), and Hansenula anomala (H. anomala) analysis showed that a syner- gistic effect is observed when the two essential oils are combined. Changes in the oil components were detected by GC-MS analysis, and the results showed that the combined Baizhu-Huangqi oil does not behave merely as the sum of two single herbs, but contains thirty-three compounds come from Baizhu, eight from Huangqi, and an additional two new components appear: Neoclovene oxide and 1,2,3,4,4a,5,6,8a-Octahydro-α,α,4a,8-tetramethyl-[2R-(2α,4aα,8aβ)]-2-naphthalenemethanol. In addition, the potential active components were analyzed by principal component regression analysis (PCR). Fifteen major components may contribute to the growth inhibition of the tested microbials and the scavenging of DPPH and ABTS·~+ radicals, while another eight may be helpful in scavenging the ABTS·~+ radical. The concentration of all potentially active components increased to different degrees in the combined oil, which may explain why the antioxidant and antimicrobial activities of the essential oils of Baizhu and Huangqi are enhanced when these two herbs are combined.