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      Antibacterial/Antifungal Activity and Synergistic Interactions between Polyprenols and Other Lipids Isolated from Ginkgo Biloba L. Leaves

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          Abstract

          Polyprenols separated from lipids are promising new components from Ginkgo biloba L. leaves (GBL). In this paper, ginkgo lipids were isolated by extraction with petroleum ether, saponification, and molecular distillation. Eight known compounds: isophytol ( 1), nerolidol ( 2), linalool ( 3), β-sitosterol acetate ( 4), β-sitosterol ( 5), stigmasterol ( 6), ergosterol ( 7), β-sitosterol-3- O- β-D-glucopyranoside ( 8) and Ginkgo biloba polyprenols (GBP) were separated from GBL by chromatography and identified mainly by NMR. The separated and identified compounds 1, 2 and 3 are reported here for the first time in GBL. The 3D-DAD-HPLC-chromatogram (190–232 nm) of GBP was recorded. This study provides new evidence as there are no previous reports on antibacterial/antifungal activities and synergistic interactions between GBP and the compounds separated from GBL lipids against Salmonella enterica, Staphylocococus aureus and Aspergillus niger. Nerolidol ( 2) showed the highest activity among all the tested samples and of all mixture groups tested the GBP with isophytol ( 1) mixture had the strongest synergistic effect against Salmonella enterica among the three tested strains. A proportion of isophytol and GBP of 38.19%:61.81% (wt/wt) was determined by mixture design as the optimal proportion for the synergistic effect of GBP with isophytol against Salmonella enterica.

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          Most cited references30

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          Antimicrobial activity of plant essential oils using food model media: efficacy, synergistic potential and interactions with food components.

          The aim of this study was to optimise the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria spp. and spoilage bacteria using food model media based on lettuce, meat and milk. The EOs evaluated were lemon balm, marjoram, oregano and thyme and their minimum inhibitory concentrations (MIC) were determined against Enterobacter spp., Listeria spp., Lactobacillus spp., and Pseudomonas spp. using the agar dilution method and/or the absorbance based microplate assay. MICs were significantly lower in lettuce and beef media than in TSB. Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs. EO combinations were investigated using the checkerboard method and Oregano combined with thyme had additive effects against spoilage organisms. Combining lemon balm with thyme yielded additive activity against Listeria strains. The effect of simple sugars and pH on antimicrobial efficacy of oregano and thyme was assessed in a beef extract and tomato serum model media. EOs retained greater efficacy at pH 5 and 2.32% sugar, but sugar concentrations above 5% did not negatively impact EO efficacy. In addition to proven antimicrobial efficacy, careful selection and investigation of EOs appropriate to the sensory profile of foods and composition of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars.
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            The fractional inhibitory concentration (FIC) index as a measure of synergy.

            The value of the FIC index as a predictor of synergy has been investigated using the antibacterial agents alafosfalin and cephalexin combined together with themselves in fully blind experiments. Under the conditions used, even weak interaction (FIC index 0.5-0.99) proved to be statistically highly significant. The use of such fully controlled blind studies would greatly enhance the credibility of many of the claims of synergy published in the literature. The representation of results as average isobolograms is only of value with combinations which show moderate to strong interaction.
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              Chemical analysis of Ginkgo biloba leaves and extracts.

              The chemical analysis and quality control of Ginkgo leaves and extracts is reviewed. Important constituents present in the medicinally used leaves are the terpene trilactones, i.e., ginkgolides A, B, C, J and bilobalide, many flavonol glycosides, biflavones, proanthocyanidins, alkylphenols, simple phenolic acids, 6-hydroxykynurenic acid, 4-O-methylpyridoxine and polyprenols. In the commercially important Ginkgo extracts some of these compound classes are no longer present. Many publications deal with the analysis of the unique terpene trilactones. They can be extracted with aqueous acetone or aqueous methanol but also supercritical fluid extraction is possible. Still somewhat problematic is their sample clean-up. Various procedures, not all of them validated, employing partitioning or SPE have been proposed. Some further development in this area can be foreseen. Separation and detection can be routinely carried out by HPLC with RI, ELSD or MS, or with GC-FID after silylation. TLC is another possibility. No quantitative procedure for flavonol glycosides has been published so far due their difficult separation and commercial unavailability. Fingerprint analysis by gradient RP-HPLC is possible. After acidic hydrolysis to the aglycones quercetin, kaempferol and isorhamnetin and separation by HPLC, quantitation is straightforward and yields by recalculation an estimation of the original total flavonol glycoside content. For biflavones, simple phenols, 6-hydroxykynurenic acid, 4-O-methylpyridoxine and polyprenols analytical procedures have been published but not all assays are yet ideal. Lately a there is a lot of interest in the analysis of the undesired alkylphenols and a few validated procedures have been published. The analysis of Ginkgo proanthocyanidins is still in its infancy and no reliable assays exist.
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                Author and article information

                Journal
                Molecules
                Molecules
                molecules
                Molecules
                MDPI
                1420-3049
                07 February 2013
                February 2013
                : 18
                : 2
                : 2166-2182
                Affiliations
                [1 ]Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, Jiangsu, China
                [2 ]National Engineering Laboratory for Biomass Chemical Utilization, Nanjing 210042, Jiangsu, China
                [3 ]Key and Open Laboratory on Forest Chemical Engineering, SFA, Nanjing 210042, Jiangsu, China
                [4 ]Key Laboratory of Biomass Energy and Material, Nanjing 210042, Jiangsu, China
                [5 ]Institute of New Technology of Forestry, CAF, Beijing 100091, China
                Author notes
                [* ] Author to whom correspondence should be addressed; E-Mail: wangczlhs@ 123456sina.com ; Tel./Fax: +86-025-8548-2471.
                Article
                molecules-18-02166
                10.3390/molecules18022166
                6269727
                23434869
                8d16fea3-7066-4b38-a51d-90fe8f31c707
                © 2013 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 28 November 2012
                : 21 January 2013
                : 31 January 2013
                Categories
                Article

                ginkgo biloba,polyprenols,lipids,antibacterial activity,antifungal activity,synergistic effect

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