| Almost all life phenomena and diseases are associated with oxidative damage byfree radicals. Researchers found that approaches from single antioxidant are notadequate to assess the health benefit of mixtures. Total antioxidant capacity in plantsand their processing products is not only attributed to additive effect, but synergisticeffect. Explore the possible mechanism(s) responsible for the synergism, which canbring the single-component research to a new level and lay a theoretical foundationfor the concomitant use of medicines, finally develop new medicines and functionalfoods from natural antioxidants. Potentilla fruticosa is a species of hardy deciduousflowering shrub in the Potentilla genus of the family, widely distribute in the northerntemperate areas. Extracts from the aerial and/or underground parts have been appliedin traditional medicine and exhibit antioxidant, antiulcerogenic, hypoglycemic,antitumor and anti-inflammatory properties. Ginkgo Biloba extracts (EGb761) iscommonly used to treat peripheral arterial disease and organic brain syndromes, theseproperties of the natural antioxidant EGb are thought to contain flavonoid substances,which can protect human body from biological free radical injuries. This studyinvestigated some credence to the concomitant use of P. fruticosa blended with EGb,which could be useful for discovering new resources for lead structures and tosupplement the traditional medicine, finally developing new medicines and functionalfoods from P. fruticosa and EGb.(1) P. fruticosa possessed the highest content of total phenolic (84.93±0.50mmolgallic acid equivalent/100g), total flavonoid (84.14±0.03mmol quercetin equivalent/100g) and antioxidant activities in DPPHIC50(16.87μg/mL), ABTS (2763.48μmolTrolox equivalent/g) and FRAP (1398.70μmol Trolox equivalent/g) capacities.(2)A bio-guided chromatographic fractionation strategy was used to obtain twoeffective fractions(C-3and D-2) from the acetone crude extract (A) of P. fruticosaleaves, DPPHIC50were5.28±0.13and4.81±0.06μg/mL； ABTS values were8314.94±7.55and5117.02±7.24μmol Trolox equivalent/g；FRAP values were3667.04±9.48and2041.11±13.12μmol Trolox equivalent/g。(3) Isobolographic analysis indicated that the combination of A+EGb had largely demonstrated synergism and5:1(A: EGb) displayed the best synergistic effect.C-3+EGb exhibited a similar result as A+EGb, synergism in DPPH and ABTS,additive in FRAP. While D-2+EGb showed only additive effect.(4) The possible mechanism behind the synergism was explored by RP-HPLC.The changes in the total phenolic and flavonoids content were also investigated.While components compositional did not seem to change in the mixture, no newpeaks appeared in the chromatogram of C-3+EGb mixture as compared to theindividual chromatogramsm, no existing peaks disappeared either.(5) Combinations of C-3and four phenolic compounds in EGb ((+)-catechin,kaempferide, quercetin and isorhamnetin) were evaluated for their antioxidantcapacities. Isorhamnetin showed synergism with C-3, and5:1exhibited the strongestsynergism in DPPH (γ=0.669) and ABTS (γ=1.249),1:1in FRAP assays (γ=1.385).Isorhamnetin was added to the other6phenolics in C-3by HPLC ((+)-catechin,caffeic acid, hyperoside, rutin, ellagic acid and quercetin) and the antioxidant capacityof mixtures was analyzed. For all combinations studied, caffeic acid+isorhamnetindisplayed the greatest synergistic effect in various ratios by three antioxidant assays,the observed values were significantly higher than the expected values (P<0.05) and1:1exhibited the strongest synergism in DPPH (γ=0.711), ABTS (γ=1.693) and FRAP(γ=1.474). Thus, interaction of phytochemicals exist in plant are likely responsible forthe synergistic effects present in Potentilla fruticosa and EGb. |
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