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Hasan Mukhtar – One of the best experts on this subject based on the ideXlab platform.

  • inhibition of ultraviolet b mediated activation of nuclear factor κb in normal human epidermal keratinocytes by green tea constituent Epigallocatechin 3 gallate
    Oncogene, 2003
    Co-Authors: Farrukh Afaq, Nihal Ahmad, Vaqar M Adhami, Hasan Mukhtar

    Abstract:

    Inhibition of ultraviolet B-mediated activation of nuclear factor κ B in normal human epidermal keratinocytes by green tea Constituent (-)-Epigallocatechin-3-gallate

  • green tea constituent Epigallocatechin 3 gallate and induction of apoptosis and cell cycle arrest in human carcinoma cells
    Journal of the National Cancer Institute, 1997
    Co-Authors: Nihal Ahmad, Denise K Feyes, Rajesh Agarwal, Hasan Mukhtar, Annaliisa Nieminen

    Abstract:

    Background and Purpose: The polyphenolic compounds present in green tea show cancer chemopreventive effects in many animal tumor models. Epidemiologic studies have also suggested that green tea consumption might be effective in the prevention of certain human cancers. We investigated the effect of green tea polyphenols and the major constituent, Epigallocatechin-3-gallate, on the induction of apoptosis (programmed cell death) and regulation of cell cycle in human and mouse carcinoma cells. Methods: Human epidermoid carcinoma cells (cell line A431), human carcinoma keratinocyte (cell line HaCaT), human prostate carcinoma cells (cell line DU145), mouse lymphoma cells (cell line L5178Y), and normal human epidermal keratinocytes (NHEKs) were used. Apoptosis was assessed by 1) the formation of internucleosomal DNA fragments by agarose gel electrophoresis, 2) confocal microscopy, and 3) flow cytometry after tagging the DNA fragments by fluorescence label. The distribution of cells in different phases of the cell cycle was analyzed by flow cytometry. Results: Treatment of A431 cells with green tea polyphenols and its components, Epigallocatechin-3-gallate, Epigallocatechin, and epicatechin-3-gallate, resulted in the formation of internucleo-somal DNA fragments, characteristic of apoptosis. Treatment with Epigallocatechin-3-gallate also resulted in apoptosis in HaCaT, L5178Y, and DU145 cells, but not in NHEK. Confocal microscopy and flow cytometry confirmed the findings. The DNA cell cycle analysis showed that in A431 cells, Epigallocatechin-3-gallate treatment resulted in arrest in the G 0 -G 1 phase of the cell cycle and a dose-dependent apoptosis. Conclusions: Green tea may protect against cancer by causing cell cycle arrest and inducing apoptosis. It needs to be evaluated in human trials.

Sirshendu De – One of the best experts on this subject based on the ideXlab platform.

  • selective extraction of Epigallocatechin gallate from green tea leaves using two stage infusion coupled with membrane separation
    Food and Bioprocess Technology, 2012
    Co-Authors: Abhishek Kumar, Barun Kumar Thakur, Sirshendu De

    Abstract:

    A novel method for the extraction of (−)Epigallocatechin gallate of high purity from green tea leaves is proposed in this study. The method comprised a two-stage water-based extraction followed by successive use of microfiltration and ultrafiltration. Microfiltration was used as a pretreatment to ultrafiltration. The best process conditions of each unit operation were estimated by performing well-planned experimentations. The clarified liquor was dried to powder by freeze drying. Chemical analyses revealed that the tea powder contained about 90% of polyphenols. The purity of (−)Epigallocatechin gallate was found to be about 80%, while its average yield was 1.22 g/l. The method outlined in this study may have remarkable importance for the bulk production of high-purity (−)Epigallocatechin gallate with potential application in pharmaceutical, cosmetic, and food-processing industries. Besides being a green process, this method can be easily scaled up for the commercial production of (−)Epigallocatechin gallate.

  • Selective Extraction of (−)Epigallocatechin Gallate from Green Tea Leaves Using Two-Stage Infusion Coupled with Membrane Separation
    Food and Bioprocess Technology, 2012
    Co-Authors: Abhishek Kumar, Barun Kumar Thakur, Sirshendu De

    Abstract:

    A novel method for the extraction of (−)Epigallocatechin gallate of high purity from green tea leaves is proposed in this study. The method comprised a two-stage water-based extraction followed by successive use of microfiltration and ultrafiltration. Microfiltration was used as a pretreatment to ultrafiltration. The best process conditions of each unit operation were estimated by performing well-planned experimentations. The clarified liquor was dried to powder by freeze drying. Chemical analyses revealed that the tea powder contained about 90% of polyphenols. The purity of (−)Epigallocatechin gallate was found to be about 80%, while its average yield was 1.22 g/l. The method outlined in this study may have remarkable importance for the bulk production of high-purity (−)Epigallocatechin gallate with potential application in pharmaceutical, cosmetic, and food-processing industries. Besides being a green process, this method can be easily scaled up for the commercial production of (−)Epigallocatechin gallate.

Maheshinie Rajapaksha – One of the best experts on this subject based on the ideXlab platform.

  • Separation of catechin constituents from five tea cultivars using high-speed counter-current chromatography
    Journal of Chromatography A, 2005
    Co-Authors: N. Savitri Kumar, Maheshinie Rajapaksha

    Abstract:

    Catechins were extracted from five different tea (Camellia sinensis L.) cultivars. High-speed counter-current chromatography was found to be an efficient method for the separation of seven catechins from the catechin extracts. High-performance liquid chromatography was used to assess the purity of the catechins isolated. Epigallocatechin gallate (EGCG), epicatechin gallate (ECG) and Epigallocatechin (EGC) of high purity (91-99%) were isolated in high yield after a single high-speed counter-current chromatography run. The two-phase solvent mixtures used for the separation of the catechin extracts were hexane:ethyl acetate:methanol:water (1:6:1:6 for TRI 2023); (1:7:1:7 for TRI 2025 and TRI 2043); (1:5:1:5 for TRI 3079) and (1:6.5:1:6.5 for TRI 4006). Fresh tea shoots from the tea cultivar TRI 2023 (150 g) gave 440 mg of 96% pure EGCG while TRI 2025 (235 g) gave 347 mg of 99% pure EGCG and 40 mg of 97% ECG, and TRI 3079 (225 g) gave 432 mg of 97% pure EGCG and 32 mg of 96% pure ECG. Tea cultivar TRI 4006 (160 g) gave EGCG (272 mg, 96% pure) and EGC (104 mg, 90% pure).1H and13C NMR chemical shifts for catechin gallate (CG), EGC, ECG, EGCG and Epigallocatechin 3,5-di-O-gallate (EGCDG) in CD3OD were also recorded. © 2005 Elsevier B.V. All rights reserved.