title: Synergistic effects and related bioactive mechanism of Potentilla fruticosa L. leaves combined with Ginkgo biloba extracts studied with microbial test system (MTS).
abstract: BACKGROUND
  Potentilla fruticosa, also called "Jinlaomei" and "Gesanghua", is widely used as folk herbs in traditional Tibetan medicine in China to treat inflammations, wounds, certain forms of cancer, diarrhoea, diabetes and other ailments. Previous research found P. fruticosa leaf extract (C-3) combined with Ginkgo biloba extracts (EGb) showed obvious synergistic effects in a variety of oxidation systems. The aim of the present study was to further confirm the synergy of P. fruticosa combined with EGb viewed from physiological bioavailability and explore the related bioactive mechanism behind the synergism.
  
  
  METHODS
  The microbial test system (MTS) was adopted to evaluate the related bioactive mechanism. The synergistic effects were evaluated by isobolographic analysis. The H2O2production rate and antioxidant enzyme (Catalase (CAT), Peroxidase (POD), Superoxide dismutase (SOD), Glutathione peroxidase (GSH-PX)) activities were determined by the colorimetric method. Enzyme gene (CAT, SOD) expression was measured by real time-PCR.
  
  
  RESULTS
  The MTS antioxidant activity results showed the combination of C-3 + EGb exhibited synergistic effects especially at the ratio 5:1. Components of isorhamnetin and caffeic acid in C-3 and EGb displayed strong antioxidant activities on MTS and their combination also showed significant synergy in promoting H2O2production. The combinations of C-3 + EGb and isorhamnetin + caffeic acid promoted CAT and SOD enzyme activities and the ratio 1:1 exhibited the strongest synergy while no obvious promotion on POD and GSH-PX enzyme activities was found. Both combinations above promoted gene expression of CAT and SOD enzymes and the ratio 1:1 exhibited the strongest synergy.
  
  
  CONCLUSIONS
  Antioxidant activity results in MTS further confirmed the significant synergy of C-3 combined with EGb and isorhamnetin combined with caffeic acid. The synergy of C-3 combined with EGb may be attributed to the combination of isorhamnetin + caffeic acid, which promoted CAT and SOD enzyme gene expression and further promoted the enzyme activities in E. coli. This study could further provide rational basis for optimizing the physiological bioavailability of P. fruticosa by using natural and safe antioxidants in low doses to produce new medicines and functional products.
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, Shaanxi, 712100, China.
authors.forename: Ze-Hua
authors.initials: ZH
authors.lastname: Liu
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, Shaanxi, 712100, China. dmwli@163.com.
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Wang
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, Shaanxi, 712100, China.
authors.forename: Su-Fang
authors.initials: SF
authors.lastname: Fan
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, Shaanxi, 712100, China. dengwuli@163.com.
authors.forename: Deng-Wu
authors.initials: DW
authors.lastname: Li
authors.affiliation: College of Forestry, Northwest A & F University, Yangling, Shaanxi, 712100, China.
authors.forename: Zi-Wen
authors.initials: ZW
authors.lastname: Luo
mesh_terms: D000975:Antioxidants / Q000494:pharmacology* / Q000627:therapeutic use; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology; D020441:Ginkgo biloba / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology*; D031987:Potentilla / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts; D006861:Hydrogen Peroxide
keywords: Ginkgo biloba extracts; Microbial test system (MTS); Potentilla fruticosa L. leaves; Real-time PCR; Synergistic mechanism