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Abstract: The ionic liquids based simultaneous ultrasonic and microwave assisted extraction (IL-UMAE) technique was first proposed and applied to isolate compounds. The ionic liquids comprising a range of four anions, five 1-alkyl-3-methylimidazolium derivatives were designed and prepared. The results suggested that varying the anion and cation both had apparent effects on the extraction of phenolics. The results also showed that irradiation power, time and solid–liquid ratio significantly affected the yields. The yields of caffeic acid and quercetin obtained by IL-UMAE were higher than those by regular UMAE. Compared with conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (8–17% enhanced) and shorter extraction time (from 5h to 30s). The results indicated ILUMAE to be a fast and efficient extraction technique. Moreover, the proposed method was validated by the reproducibility and recovery experiments. The ILUMAE method provided good recoveries (from 96.1% to 105.3%) with RSD lower than 5.2%, which indicated that the proposed method was credible. Based on the designable nature of ionic liquids, and the rapid and highly efficient performance of the proposed approach, ILUMAE provided a new alternative for preparation of various useful substances from solid samples. [Copyright &y& Elsevier]

Abstract: The chemical composition and antibacterial activities of burdock leaves fractions against six food-related bacteria (Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli, Shigella dysenteriae and Salmonella typhimurium) were first investigated. The burdock leaves extract was fractioned with ethyl acetate, n-butanol and water, named as EF, BF and WF. The data from minimum inhibitory concentration (MIC) values showed that EF and other fractions effectively inhibited the growth of all test bacterial pathogens, the antibacterial activity of EF being much greater than BF and WF. The time–kill study indicated that EF exhibited significant bactericidal activity against all the six pathogens. At 12h, EF was bactericidal for 4/6, 6/6 and 6/6 strains at 1×MIC, 3×MIC and 5×MIC, respectively. For all the fractions, the antibacterial capacity had a significant correlation with total phenolic content, suggesting that the activities were probably due to the combined action of phenolic compounds. The phenolic compounds of the fractions were then identified for the first time. After activity-guide fractionation and separation by flash chromatogram, two purified active compounds (chlorogenic acid, rutin) were obtained, and identified by UPLC–MS/MS. The ethyl acetate fraction based on its lower MIC values, concentration and time-dependent antibacterial and bactericidal activities could be useful in control of foodborne bacterial pathogens. [Copyright &y& Elsevier]

Abstract: The simultaneous ultrasonic and microwave assisted extraction (UMAE) technique was first employed to obtain phenolics. The effects of UMAE variables including extraction time, microwave power, and solvent to solid radio on the yield of phenolics were investigated. The optimized conditions were as follows: solvent to solid ratio was 20:1 (ml/g), extraction time was 30s, microwave power was 500W and two times of extraction. Moreover, the phenolic yield of UMAE was higher than that by maceration, indicating a significant reduction of extraction time and an improvement of efficiency. The phenomenon is related to the strong disruption of leaf tissue structure by microwave induced expansion and ultrasonic shaking, which had been observed with the scanning electron microscopy. The phenolic compositions of the extract was then identified by ultra performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS), 10 compounds had been characterized, providing a more complete identification of phenolic compounds in burdock leaves than previously reported. The occurrence of benzoic acid and p-coumaric acid is reported for the first time. This study suggests that UMAE is a good alternative for the extraction of phenolics, with a great potential for industrial application. Also, UMAE provides a new sample preparation technique for characterization of the phenolic compounds from plants. [Copyright &y& Elsevier]

Abstract: The simultaneous ultrasonic/microwave assisted extraction (UMAE) of inulin and production of phenols-rich dietary fibre powder from burdock root was studied. It was found that UMAE required a much shorter extraction time than conventional stirring extraction. And the recovery of inulin increased with the increase of microwave power as well as solvent to solid ratio. A comparison of scanning electron microscopy images of raw and simultaneous ultrasonic/microwave treated burdock root indicated microfractures and disruption of cell walls in burdock root flakes. The dietary fibre powder prepared from the residue of burdock root after inulin extraction was rich in phenols (302.62mg GAE/100g powder). The results showed that drying temperature in the selected range did not significantly affect the hydration properties. The relatively high water retention capacity, swelling capacity and oil-holding capacity of the dietary fibre powder indicated its broad use as a modifier of properties of formulated products. [Copyright &y& Elsevier]

The aim of this study was to investigate the antimicrobial activity of burdock leaf and screen the antimicrobial compounds from burdock leaf based on metabolomics. The crystal violet assay indicated that 34 % ethanol elution fraction of burdock leaf could completely inhibit biofilm formation of Salmonellaty phimurium at a concentration of 1 mg/ml. Then, the chemical composition of burdock leaf fraction was analyzed by UPLC-MS, and 10 active compounds (chlorogenic acid, caffeic acid, p-coumaric acid, quercetin, ursolic acid, rutin, luteolin, crocin, benzoic acid, tenacissoside I) were identified. Lastly, UPLC-MS analysis was applied to obtain the metabolic fingerprints of burdock leaf fractions before and after inhibiting the biofilm of S. phimurium. The metabolic fingerprints were transformed into data with the software MarkerLynx and analyzed with principle component analysis and partial least squares discriminant analysis. Then, 43 variables were screened as potential anti-biofilm ingredients. Among them, chlorogenic acid and quercetin were confirmed as potential anti-biofilm compounds in burdock leaf. It provided data basic for the study of anti-biofilm compounds in burdock leaves, as well as provided a new and convenient method for fast screening of anti-biofilm ingredients from natural plants. [ABSTRACT FROM AUTHOR]

The inhibition effects of burdock leaf ethanol fraction on the viability, biofilm formation of food-related bacteria and the mechanism were first investigated. The results showed that burdock leaf ethanol fraction significantly inhibited the formation of biofilm by Staphylococcus aureus and Listeria monocytogenes. The lowest concentration of the fraction that showed 100 % inhibition on the formation of L. monocytogenes biofilm was 2.50 mg/ml, which was equal to the minimum inhibitory concentration (MIC) against bacterial growth. As for S. aureus, the lowest concentration of burdock leaf fraction that completely inhibited (100 %) the formation of biofilm was found to be 1.25 mg/ml, which was lower than MIC of the fraction (2.5 mg/ml). Thus, the biofilm inhibition effect of burdock leaf fraction against S. aureus was not completely due to the inhibition on bacteria growth. Then, the effects of burdock leaf fraction on quorum sensing signals were evaluated through GC-MS/MS analysis. The results indicated that burdock leaf fraction interfered with quorum sensing system and changed the composition of signaling molecules, thereby affecting the function of the quorum sensing system, significantly inhibiting the formation of biofilm. Then, the chemical composition of burdock leaf fraction was analyzed by ultra performance liquid chromatography (UPLC)-MS/MS and eight active compounds were identified. The burdock leaf fraction based on its interfering with quorum sensing systems and the significant inhibition on the formation of biofilm could be highly useful in control of biofilms. [ABSTRACT FROM AUTHOR]

Abstract: Enrichment of burdock leaf components and the inhibition effect of the obtained 7 burdock leaf fractions on formation of biofilm have been evaluated for the first time. Firstly, burdock leaf fractions were obtained though separation of burdock leaf extracts by macroporous resin column chromatography, and four fractions were obtained, namely, water elution fraction, 20%, 34% and 70% ethanol eluted fractions. It was found that the 20% and 34% ethanol fractions both significantly inhibited the formation of biofilm by Escherichia coli, with IC50 of 1.10 and 1.01 mg/ml, respectively. The 70% ethanol elution fraction exhibited the strongest inhibitory activity against biofilm formation with an IC50 of 0.017 mg/ml. In order to obtain more fractions with higher inhibitory activity, polyamide resin was used to further purify the 34% ethanol elution fraction. The second chromatography separation significant improved the activity of burdock leaf fractions and the IC50 of a new fraction was 0.03 mg/ml. The phenolic contents of the fractions ranged from 7.5 to 369.7 mg/g and there was a high correlation between the anti-biofilm capacity and phenolic contents, except for 70% ethanol fraction. Scanning electron microscopy (SEM) observation showed that there was no biofilm formation for cultures treated with burdock leaf fraction, conforming the significant inhibition activity of burdock leaf fraction against the formation of biofilm. The results suggest that separation and enrichment of the active ingredients could significantly improve the activities of fractions and the obtained burdock leaf fractions provide new alternatives for control of biofilms. [Copyright &y& Elsevier]