| Food preservatives are indispensable as additives in food industry, according to theirorigin, it was divided into two categories: chemical synthesis preservatives and naturalpreservatives. Chemical synthesis preservatives are harmful to humans to differing degrees.Natural preservatives are favored because of its unique natural and safe, and it has becomethe development trend in preservative technology, meanwhile the development ofantimicrobial resistance and non-toxic food natural preservative turn to a research hotspotof researchers around the world. Lonicera japonica Thunb leaves,which is the leaves ofhoneysuckle, rich of effective components, such as organic acids, flavonoids and iridoidglycosides,which with a wide range of anti-microbial effects, for instance there is a certaininhibitory effect on bacteria which have an important impact on hazards of food hygiene,safety, and clinical medicine. In addition, Lonicera japonica Thunb leaves have largeyields and resources are abundant. Therefore, extracting and screening antibacterialsubstances have great theoretical significance and practical value from Lonicera japonicaThunb leaves. In the present investigation, Lonicera japonica Thunb leaves selected as rawmaterial to optimal extraction method for antibacterial ingredients, to screen antibacterialmonomer compounds and identify the structure, and to optimal drying method, for providea theoretical basis to understand the characteristics of antibacterial actives and improve itscomprehensive utilization.1. In vitro antibacterial test as evaluation index, study on extraction process of theantibacterial active ingredient and its MIC and MBC from Lonicera japonica Thunb leaves(1) Compare reflux extraction method, ultrasonic assisted extraction and Soxhletextraction effect on extract bacteriostatic active ingredients from Lonicera japonica Thunbleaves, the reflux method selected at last.(2) Through the single factor experiment and orthogonal experiment, the optimumextraction process is extraction temperature70°C, ethanol solubility60%, solid to liquidratio of1:15and extraction time1.5h.(3) Susceptibility test showed MIC is250μg/g and500μg/g for Staphylococcus aureusand Escherichia coli, respectively. MBC is500μg/g and1000μg/g for Staphylococcusaureus and Escherichia coli.2. Solvent–solvent partitioning and Chromatographic methods to screen the activesubstances from Lonicera japonica Thunb leaves.(1) The crude extract of L. Japonica leaves were solvent–solvent partitioned to obtainpetroleum ether fraction, chloroform fraction, ethyl acetate fraction, n-butyl alcoholfraction and remainder fraction (J1-J5, respectively) and then compared for antibacterialactivity. All of the fractions displayed considerable antibacterial activity against the tested bacteria, and the highest inhibition was found in the ethyl acetate fraction (J3), followed bythe n-butyl alcohol fraction (J4).(2) The J3was separated2fractions (J3A and J3B) using HPD500by28%and55%ethanol concentrations, meanwhile J3B exhibited greater antibacterial potency than J3A.J3B was chromatographed a second time over HPD500by42%and55%ethanolconcentrations to yield the J3B1and J3B2subfractions, and J3B2was the more activesubfraction.(3) J3A, J3B1and J3B2were further purified to identify active constituents bySephadex LH-20, HPD500and polyamide, five monomer substances were obtained andstructure were identified,ie.3-O-caffeoylquinic, Luteoloside, secoxyloganin,3,5-di-O-caffeoylquinic acid,4,5-di-O-caffeoylquinic acid, respectively.Among five monomercompounds3,5-di-O-caffeoylquinic acid and4,5-di-O-caffeoylquinic acid possessed thehighest antimicrobial activity, and Luteoloside have the similar effect, followed by3-O-caffeoylquinic acid, secoxyloganin relatively poor.3. Compare different drying methods effects on Lonicera japonica Thunb leaves, Theresults showed that different drying methods will affect the appearance traits, the activeingredients and the antibacterial activity, the best drying method was blast drying, followedby vacuum drying... |
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