Displaying publications 1 - 20 of 40 in total

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  1. Spectrophotometric determination of germanium with Catechol Violet and cetyltrimethylammonium bromide
    Leong CL
    Talanta, 1971 Aug;18(8):845-8.
    PMID: 18960953
    A ternary complex between germanium, Catechol Violet (CV) and cetyltrimethylanunoniuni bromide is proposed for the determination of germanium. The stoichiometric ratio Ge:CV is 1:2. Beer's law is obeyed from 0.1 to 1.0 ppm of Ge. The method is highly selective. Interference from Sn(IV), Fe(III), Bi(III), Cr(VI), Mo(VI), V(V) and Sb(III) in mg amounts is eliminated by extracting the germanium into carbon tetrachloride from 9M HC1 and then stripping into water before the photometric determination.
    Matched MeSH terms: Catechols
  2. Hexamethylenetetramine-4-nitrocatechol-water (1/2/1)
    Chantrapromma S, Usman A, Fun HK, Poh BL, Karalai C
    Acta Crystallogr C, 2002 Nov;58(Pt 11):o675-7.
    PMID: 12415179
    In the title adduct, 1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane-4-nitrobenzene-1,2-diol-water (1/2/1), C(6)H(12)N(4).2C(6)H(5)NO(4).H(2)O, the hexamethylenetetramine molecule acts as an acceptor of intermolecular O-H.N hydrogen-bonding interactions from the water molecule and the hydroxy groups of one of the two symmetry-independent 4-nitrocatechol molecules. The structure is built from molecular layers which are stabilized by three intermolecular O-H.O, two intermolecular O-H.N and four intermolecular C-H.O hydrogen bonds. The layers are further interconnected by one additional intermolecular O-H.N and two intermolecular C-H.O hydrogen bonds.
    Matched MeSH terms: Catechols
  3. Effects of aminoacids on the autooxidation of 3,5-di-tert-butylcatechol in the presence of surface-active copper(II) complexes
    Lim YY, Liew LP
    J Colloid Interface Sci, 2002 Nov 15;255(2):425-7.
    PMID: 12505092
    The rate of autooxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) in the presence of micelles formed from mixing equal concentrations of [Cu(C(12)-tmed)Br(2)] (where C(12)-tmed is N,N,N'-trimethyl-N'-dodecylethylenediamine) and several amino acids has been investigated. It was found that the rate in air-saturated solution is very much dependent on pH, which affects the availability of copper(II) coordination site for the catechol and the degree of micellization. At a given pH, the rates in [Cu(C(12)-tmed)Br(2)] micellar media are greatly enhanced in the presence sodium halide.
    Matched MeSH terms: Catechols/chemistry*
  4. Chitosan-based tyrosinase optical phenol biosensor employing hybrid nafion/sol-gel silicate for MBTH immobilization
    Abdullah J, Ahmad M, Heng LY, Karuppiah N, Sidek H
    Talanta, 2006 Oct 15;70(3):527-32.
    PMID: 18970803 DOI: 10.1016/j.talanta.2005.12.061
    The development of an optical biosensor based on immobilization of 3-methyl-2-benzothiazolinone hydrazone (MBTH) in hybrid nafion/sol-gel silicate film and tyrosinase in chitosan film for the detection of phenolic compounds has been described. Tyrosinase was immobilized in chitosan film deposited on the hybrid nafion/sol-gel silicate film containing MBTH. The enzymatic oxidation product of phenolic compounds were stabilized through formation of adduct with MBTH to produce a maroon color adduct. The color intensity of adduct was found to increase proportionally with the increase of the substrate concentrations after 5min exposure. The linearity of the biosensor towards phenol, catechol and m-cresol were in the respective concentration range of 0.5-7.0, 0.5-10.0 and 1.0-13.0mg/L with detection limit of 0.18, 0.23 and 0.43mg/L, respectively. The biosensor shows a good stability for at least 3 months.
    Matched MeSH terms: Catechols
  5. An Optical Biosensor based on Immobilization of Laccase and MBTH in Stacked Films for the Detection of Catechol
    Abdullah J, Ahmad M, Heng LY, Karuppiah N, Sidek H
    Sensors (Basel), 2007 Oct 11;7(10):2238-2250.
    PMID: 28903224 DOI: 10.3390/s7102238
    The fabrication of an optical biosensor by using stacked films where 3-methyl-2-benzothiazolinone hydrazone (MBTH) was immobilized in a hybrid nafion/sol-gelsilicate film and laccase in a chitosan film for the detection of phenolic compounds wasdescribed. Quinone and/or phenoxy radical product from the enzymatic oxidation ofphenolic compounds was allowed to couple with MBTH to form a colored azo-dye productfor spectrophometric detection. The biosensor demonstrated a linear response to catecholconcentration range of 0.5-8.0 mM with detection limit of 0.33 mM and response time of10 min. The reproducibility of the fabricated biosensor was good with RSD value of 5.3 %(n = 8) and stable for at least 2 months. The use of the hybrid materials of nafion/sol-gelsilicate to immobilize laccase has altered the selectivity of the enzyme to various phenoliccompounds such as catechol, guaicol, o-cresol and m-cresol when compared to the non-immobilized enzyme. When immobilized in this hybrid film, the biosensor response onlyto catechol and not other phenolic compounds investigated. Immobilization in this hybridmaterial has enable the biosensor to be more selective to catechol compared with the non-immobilized enzyme. This shows that by a careful selection of different immobilizationmatrices, the selectivity of an enzyme can be modified to yield a biosensor with goodselectivity towards certain targeted analytes.
    Matched MeSH terms: Catechols
  6. Photocatalytic treatment of 4-chlorophenol in aqueous ZnO suspensions: intermediates, influence of dosage and inorganic anions
    Gaya UI, Abdullah AH, Zainal Z, Hussein MZ
    J Hazard Mater, 2009 Aug 30;168(1):57-63.
    PMID: 19268454 DOI: 10.1016/j.jhazmat.2009.01.130
    The photocatalytically driven removal of eco-persistent 4-chlorophenol from water using ZnO is reported here. Kinetic dependence of transformation rate on operating variables such as initial 4-chlorophenol concentration and photocatalyst doses was investigated. A complete degradation of 4-chlorophenol at 50 mg L(-1) levels was realised in 3h. Analytical profiles on 4-chlorophenol transformation were consistent with the best-line fit of the pseudo zero-order kinetics. The addition of small amounts of inorganic anions as SO(4)(2-), HPO(4)(-), S(2)O(8)(2-) and Cl(-) revealed two anion types: active site blockers and rate enhancers. Fortunately, Cl(-) and SO(4)(2-) commonly encountered in contaminated waters enhanced the rate of 4-chlorophenol degradation. The reaction intermediates and route to 4-chlorophenol mineralisation were elucidated by combined RP-HPLC and GC-MS methods. In addition to previously reported pathway products of 4-chlorophenol photo-oxidation catechol was detected. A radical mechanism involving o-hydroxylation is proposed to account for the formation of catechol.
    Matched MeSH terms: Catechols
  7. Identification of metabolites from phenanthrene oxidation by phenoloxidases and dioxygenases of Polyporus sp. S133
    Hadibarata T, Tachibana S, Askari M
    J Microbiol Biotechnol, 2011 Mar;21(3):299-304.
    PMID: 21464602
    Phenanthrene degradation by Polyporus sp. S133, a new phenanthrene-degrading strain, was investigated in this work. The analysis of degradation was performed by calculation of the remaining phenanthrene by gas chromatography-mass spectrometry. When cells were grown in phenanthrene culture after 92 h, all but 200 and 250 mg/l of the phenanthrene had been degraded. New metabolic pathways of phenanthrene and a better understanding of the phenoloxidases and dioxygenase mechanism involved in degradation of phenanthrene were explored in this research. The mechanism of degradation was determined through identification of the several metabolites; 9,10-phenanthrenequinone, 2,2'-diphenic acid, salicylic acid, and catechol. 9,10-Oxidation and ring cleavage to give 9,10-phenanthrenequinone is the major fate of phenanthrene in ligninolytic Polyporus sp. S133. The identification of 2,2'-diphenic acid in culture extracts indicates that phenanthrene was initially attacked through dioxigenation at C9 and C10 to give cis-9,10-dihydrodiol. Dehydrogenation of phenanthrene-cis-9,10-dihydrodiol to produce the corresponding diol, followed by ortho-cleavage of the oxygenated ring, produced 2,2'-diphenic acid. Several enzymes (manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase, and 2,3-dioxygenase) produced by Polyporus sp. S133 was detected during the incubation. The highest level of activity was shown at 92 h of culture.
    Matched MeSH terms: Catechols/analysis
  8. Detection of toluene degradation in bacteria isolated from oil contaminated soils
    Ainon Hamzah, Tavakoli A, Amir Rabu
    Sains Malaysiana, 2011;40:1231-1235.
    Toluene (C7H8) a hydrocarbon in crude oil, is a common contaminant in soil and groundwater. In this study, the ability to degrade toluene was investigated from twelve bacteria isolates which were isolated from soil contaminated with oil. Out of 12 bacterial isolates tested, most of Pseudomonas sp. showed the capability to grow in 1 mM of toluene compared with other isolates on the third day of incubation. Based on enzyme assays towards toluene monooxygenase, Pseudomonas aeruginosa UKMP-14T and Bacillus cereus UKMP-6G were shown to have the highest ability to degrade toluene. The toluene monoxygenase activity was analysed by using two calorimetric methods, Horseradish peroxidase (HRP) and indole-indigo. Both of the methods measured the production of catechol by the enzymatic reaction of toluene monooxygenase. In the HRP assay, the highest enzyme activity was 0.274 U/mL, exhibited by Pseudomonas aeruginosa UKMP-14T. However, for indole-indigo assay, Bacillus cereus UKMP-6G produced the highest enzyme activity of 0.291 U/ml. Results from both experiments showed that Pseudomonas aeruginosa UKMP-14T and Bacillus cereus UKMP-6G were able to degrade toluene.
    Matched MeSH terms: Catechols
  9. 6-Shogaol inhibits breast and colon cancer cell proliferation through activation of peroxisomal proliferator activated receptor γ (PPARγ)
    Tan BS, Kang O, Mai CW, Tiong KH, Khoo AS, Pichika MR, et al.
    Cancer Lett, 2013 Aug 9;336(1):127-39.
    PMID: 23612072 DOI: 10.1016/j.canlet.2013.04.014
    6-Shogaol has been shown to possess many antitumor properties including inhibition of cancer cell growth, inhibition of cancer metastasis, induction of apoptosis in cancer cells and induction of cancer cell differentiation. Despite its prominent antitumor effects, the direct molecular target of 6-shogaol has remained elusive. To identify the direct targets of 6-shogaol, a comprehensive antitumor profile of 6-shogaol (NSC752389) was tested in the NCI-60 cell line in an in vitro screen. The results show that 6-shogaol is COMPARE negative suggesting that it functions via a mechanism of action distinct from existing classes of therapeutic agents. Further analysis using microarray gene profiling and Connectivity Map analysis showed that MCF-7 cells treated with 6-shogaol display gene expression signatures characteristic of peroxisome proliferator activated receptor γ (PPARγ) agonists, suggesting that 6-shogaol may activate the PPARγ signaling pathway for its antitumor effects. Indeed, treatment of MCF-7 and HT29 cells with 6-shogaol induced PPARγ transcriptional activity, suppressed NFκB activity, and induced apoptosis in breast and colon cancer cells in a PPARγ-dependent manner. Furthermore, 6-shogaol is capable of binding to PPARγ with a binding affinity comparable to 15-delta prostaglandin J2, a natural ligand for PPARγ. Together, our findings suggest that the antitumor effects of 6-shogaol are mediated through activation of PPARγ and imply that activation of PPARγ might be beneficial for breast and colon cancer treatment.
    Matched MeSH terms: Catechols/pharmacology*
  10. Fluorene biodegradation and identification of transformation products by white-rot fungus Armillaria sp. F022
    Hadibarata T, Kristanti RA
    Biodegradation, 2014 Jun;25(3):373-82.
    PMID: 24114532 DOI: 10.1007/s10532-013-9666-x
    A diverse surfactant, including the nonionic Tween 80 and Brij 30, the anionic sodium dodecyl sulphate, the cationic surfactant Tetradecyltrimethylammonium bromide, and biosurfactant Rhamnolipid were investigated under fluorine-enriched medium by Armilaria sp. F022. The cultures were performed at 25 °C in malt extract medium containing 1 % of surfactant and 5 mg/L of fluorene. The results showed among the tested surfactants, Tween-80 harvested the highest cell density and obtained the maximum specific growth rate. This due Tween-80 provide a suitable carbon source for fungi. Fluorane was also successfully eliminated (>95 %) from the cultures within 30 days in all flasks. During the experiment, laccase production was the highest among other enzymes and Armillaria sp. F022-enriched culture containing Non-ionic Tween 80 showed a significant result for laccase activity (1,945 U/L). The increased enzyme activity was resulted by the increased biodegradation activity as results of the addition of suitable surfactants. The biotransformation of fluorene was accelerated by Tween 80 at the concentration level of 10 mg/L. Fluorene was initially oxidized at C-2,3 positions resulting 9-fluorenone. Through oxidative decarboxylation, 9-fluorenone subjected to meta-cleavage to form salicylic acid. One metabolite detected in the end of experiment, was identified as catechol. Armillaria sp. F022 evidently posses efficient, high effective degrader and potential for further application on the enhanced bioremediation technologies for treating fluorene-contaminated soil.
    Matched MeSH terms: Catechols/metabolism
  11. Characteristic fingerprint based on gingerol derivative analysis for discrimination of ginger (Zingiber officinale) according to geographical origin using HPLC-DAD combined with chemometrics
    Yudthavorasit S, Wongravee K, Leepipatpiboon N
    Food Chem, 2014 Sep 01;158:101-11.
    PMID: 24731320 DOI: 10.1016/j.foodchem.2014.02.086
    Chromatographic fingerprints of gingers from five different ginger-producing countries (China, India, Malaysia, Thailand and Vietnam) were newly established to discriminate the origin of ginger. The pungent bioactive principles of ginger, gingerols and six other gingerol-related compounds were determined and identified. Their variations in HPLC profiles create the characteristic pattern of each origin by employing similarity analysis, hierarchical cluster analysis (HCA), principal component analysis (PCA) and linear discriminant analysis (LDA). As results, the ginger profiles tended to be grouped and separated on the basis of the geographical closeness of the countries of origin. An effective mathematical model with high predictive ability was obtained and chemical markers for each origin were also identified as the characteristic active compounds to differentiate the ginger origin. The proposed method is useful for quality control of ginger in case of origin labelling and to assess food authenticity issues.
    Matched MeSH terms: Catechols/chemistry*
  12. Fulltext Tocotrienol-rich fraction, [6]-gingerol and epigallocatechin gallate inhibit proliferation and induce apoptosis of glioma cancer cells
    Rahman AA, Makpol S, Jamal R, Harun R, Mokhtar N, Ngah WZ
    Molecules, 2014 Sep 12;19(9):14528-41.
    PMID: 25221872 DOI: 10.3390/molecules190914528
    Plant bioactives [6]-gingerol (GING), epigallocatechin gallate (EGCG) and asiaticoside (AS) and vitamin E, such as tocotrienol-rich fraction (TRF), have been reported to possess anticancer activity. In this study, we investigated the apoptotic properties of these bioactive compounds alone or in combination on glioma cancer cells. TRF, GING, EGCG and AS were tested for cytotoxicity on glioma cell lines 1321N1 (Grade II), SW1783 (Grade III) and LN18 (Grade IV) in culture by the (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt) (MTS) assay. With the exception of AS, combinations of two compounds were tested, and the interactions of each combination were evaluated by the combination index (CI) using an isobologram. Different grades of glioma cancer cells showed different cytotoxic responses to the compounds, where in 1321N1 and LN18 cells, the combination of EGCG + GING exhibited a synergistic effect with CI = 0.77 and CI = 0.55, respectively. In contrast, all combinations tested (TRF + GING, TRF + EGCG and EGCG + GING) were found to be antagonistic on SW1783 with CI values of 1.29, 1.39 and 1.39, respectively. Combined EGCG + GING induced apoptosis in both 1321N1 and LN18 cells, as evidenced by Annexin-V FITC/PI staining and increased active caspase-3. Our current data suggests that the combination of EGCG + GING synergistically induced apoptosis and inhibits the proliferation 1321N1 and LN18 cells, but not SW1783 cells, which may be due to their different genetic profiles.
    Matched MeSH terms: Catechols/administration & dosage*
  13. Fulltext Antioxidant activity of hispidin oligomers from medicinal fungi: a DFT study
    El Hassane A, Shah SA, Hassan NB, El Moussaoui N, Ahmad R, Zulkefeli M, et al.
    Molecules, 2014;19(3):3489-507.
    PMID: 24662069 DOI: 10.3390/molecules19033489
    Hispidin oligomers are styrylpyrone pigments isolated from the medicinal fungi Inonotus xeranticus and Phellinus linteus. They exhibit diverse biological activities and strong free radical scavenging activity. To rationalize the antioxidant activity of a series of four hispidin oligomers and determine the favored mechanism involved in free radical scavenging, DFT calculations were carried out at the B3P86/6-31+G (d, p) level of theory in gas and solvent. The results showed that bond dissociation enthalpies of OH groups of hispidin oligomers (ArOH) and spin density delocalization of related radicals (ArO•) are the appropriate parameters to clarify the differences between the observed antioxidant activities for the four oligomers. The effect of the number of hydroxyl groups and presence of a catechol moiety conjugated to a double bond on the antioxidant activity were determined. Thermodynamic and kinetic studies showed that the PC-ET mechanism is the main mechanism involved in free radical scavenging. The spin density distribution over phenoxyl radicals allows a better understanding of the hispidin oligomers formation.
    Matched MeSH terms: Catechols/chemistry
  14. Fulltext Assessment of bioactive compounds, nutritional composition and antioxidant activity of Malaysian young ginger ( Zingiber officinale Roscoe)
    Mojani, M.S., Ghasemzadeh, A., Rahmat, A., Loh, S.P., Ramasamy, R.
    International Food Research Journal, 2014;21(5):1931-1935.
    MyJurnal
    In current work, the nutritional composition, bioactive compounds, total phenolic contents and anti-oxidant activity of young Malaysian ginger rhizome were investigated. Proximate analysis and high performance liquid chromatography (HPLC) recruited to determine nutritional composition and bioactive compounds. The total flavonoid (TF) and total phenolic contents (TPC) of ginger rhizome were determined by aluminium chloride calorimetric assay and Folin-Ciocalteau reagent, respectively. 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method were used to measure antioxidant capacity. The rhizome contained high moisture content and low level of carbohydrate and energy. 6-gingerol was the most abundant component in the selected ginger, and total flavonoid and phenolic content were reported to be 3.66±0.45 mg gallic acid/g and 10.22±0.87 mg quercetin/g of dry weight of rhizome, respectively. The rhizome also showed lower antioxidant activity than controls, with the IC 50 value of 46.5 vs. 15.5 for α-tocopherol and 22 for BHT. The results of this study predicted that the young ginger rhizome originated from Malaysia may exhibit anti-oxidative and anti-inflammatory potentials due to high levels of gingerols, total flavonoid and phenolic compounds and antioxidant capacity.
    Matched MeSH terms: Catechols
  15. Pyroligneous acid-the smoky acidic liquid from plant biomass
    Mathew S, Zakaria ZA
    Appl Microbiol Biotechnol, 2015 Jan;99(2):611-22.
    PMID: 25467926 DOI: 10.1007/s00253-014-6242-1
    Pyroligneous acid (PA) is a complex highly oxygenated aqueous liquid fraction obtained by the condensation of pyrolysis vapors, which result from the thermochemical breakdown or pyrolysis of plant biomass components such as cellulose, hemicellulose, and lignin. PA produced by the slow pyrolysis of plant biomass is a yellowish brown or dark brown liquid with acidic pH and usually comprises a complex mixture of guaiacols, catechols, syringols, phenols, vanillins, furans, pyrans, carboxaldehydes, hydroxyketones, sugars, alkyl aryl ethers, nitrogenated derivatives, alcohols, acetic acid, and other carboxylic acids. The phenolic components, namely guaiacol, alkyl guaiacols, syringol, and alkyl syringols, contribute to the smoky odor of PA. PA finds application in diverse areas, as antioxidant, antimicrobial, antiinflammatory, plant growth stimulator, coagulant for natural rubber, and termiticidal and pesticidal agent; is a source for valuable chemicals; and imparts a smoky flavor for food.
    Matched MeSH terms: Catechols/chemistry
  16. Supramolecular interaction of 6-shogaol, a therapeutic agent of Zingiber officinale with human serum albumin as elucidated by spectroscopic, calorimetric and molecular docking methods
    Feroz SR, Mohamad SB, Lee GS, Malek SN, Tayyab S
    Phytomedicine, 2015 Jun 01;22(6):621-30.
    PMID: 26055127 DOI: 10.1016/j.phymed.2015.03.016
    BACKGROUND: 6-Shogaol, one of the main bioactive constituents of Zingiber officinale has been shown to possess various therapeutic properties. Interaction of a therapeutic compound with plasma proteins greatly affects its pharmacokinetic and pharmacodynamic properties.

    PURPOSE: The present investigation was undertaken to characterize the interaction between 6-shogaol and the main in vivo transporter, human serum albumin (HSA).

    METHODS: Various binding characteristics of 6-shogaol-HSA interaction were studied using fluorescence spectroscopy. Thermal stability of 6-shogaol-HSA system was determined by circular dichroism (CD) and differential scanning calorimetric (DSC) techniques. Identification of the 6-shogaol binding site on HSA was made by competitive drug displacement and molecular docking experiments.

    RESULTS: Fluorescence quench titration results revealed the association constant, Ka of 6-shogaol-HSA interaction as 6.29 ± 0.33 × 10(4) M(-1) at 25 ºC. Values of the enthalpy change (-11.76 kJ mol(-1)) and the entropy change (52.52 J mol(-1) K(-1)), obtained for the binding reaction suggested involvement of hydrophobic and van der Waals forces along with hydrogen bonds in the complex formation. Higher thermal stability of HSA was noticed in the presence of 6-shogaol, as revealed by DSC and thermal denaturation profiles. Competitive ligand displacement experiments along with molecular docking results suggested the binding preference of 6-shogaol for Sudlow's site I of HSA.

    CONCLUSION: All these results suggest that 6-shogaol binds to Sudlow's site I of HSA through moderate binding affinity and involves hydrophobic and van der Waals forces along with hydrogen bonds.

    Matched MeSH terms: Catechols/chemistry*
  17. Fulltext γ-Tocotrienol and 6-Gingerol in Combination Synergistically Induce Cytotoxicity and Apoptosis in HT-29 and SW837 Human Colorectal Cancer Cells
    Yusof KM, Makpol S, Jamal R, Harun R, Mokhtar N, Ngah WZ
    Molecules, 2015 Jun 03;20(6):10280-97.
    PMID: 26046324 DOI: 10.3390/molecules200610280
    Numerous bioactive compounds have cytotoxic properties towards cancer cells. However, most studies have used single compounds when bioactives may target different pathways and exert greater cytotoxic effects when used in combination. Therefore, the objective of this study was to determine the anti-proliferative effect of γ-tocotrienol (γ-T3) and 6-gingerol (6G) in combination by evaluating apoptosis and active caspase-3 in HT-29 and SW837 colorectal cancer cells. MTS assays were performed to determine the anti-proliferative and cytotoxicity effect of γ-T3 (0-150 µg/mL) and 6G (0-300 µg/mL) on the cells. The half maximal inhibitory concentration (IC50) value of 6G+ γ-T3 for HT-29 was 105 + 67 µg/mL and for SW837 it was 70 + 20 µg/mL. Apoptosis, active caspase-3 and annexin V FITC assays were performed after 24 h of treatment using flow cytometry. These bioactives in combination showed synergistic effect on HT-29 (CI: 0.89 ± 0.02,) and SW837 (CI: 0.79 ± 0.10) apoptosis was increased by 21.2% in HT-29 and 55.4% in SW837 (p < 0.05) after 24 h treatment, while normal hepatic WRL-68 cells were unaffected. Increased apoptosis by the combined treatments was also observed morphologically, with effects like cell shrinkage and pyknosis. In conclusion, although further studies need to be done, γ-T3 and 6G when used in combination act synergistically increasing cytotoxicity and apoptosis in cancer cells.
    Matched MeSH terms: Catechols/pharmacology*
  18. Fulltext Partial purification and characterization of polyphenol oxidase from round brinjal (S. melongena var. depressum)
    Ng, A.W.R., Wong, C.W.
    International Food Research Journal, 2015;22(2):826-831.
    MyJurnal
    Polyphenol oxidase (PPO) catalyzes the conversion of phenolic compounds into o-quinones which will lead to food browning. This phenomenon causes huge implications on food industries, as it degrades food quality over time. By combining both ammonium sulphate precipitation and gel filtration chromatography, PPO was partially purified up to 5.26-fold with 11.23% yield. The enzyme activity was 5120 EU/mL using 4-methylcatechol as substrate. Maximal PPO activity was found at 30oC, pH 5.0 for 4-methylcatechol and 40°C, pH 6.0 for catechol. The PPO showed a higher affinity towards 4-methylcatechol but higher thermal stability when reacting with catechol. The Km and Vmax values were 5.00 mM, 2000 EU/ml for 4-methylcatechol and 10.79 mM, 526.32 EU/ml for catechol. Energy for inactivation (Ea) obtained using 4-methylcatechol and catechol were 12.57 kJ/mol and 14.23 kJ/mol from respective substrates. Sodium disulfite was a better inhibitor where 79.17% of PPO inhibition was achieved. The isolation and characterization of round brinjal PPO serves as a guideline to predict the behavior of enzyme, leading to effective prevention of its browning during processing and storage.
    Matched MeSH terms: Catechols
  19. Fulltext Optimization protocol for the extraction of 6-gingerol and 6-shogaol from Zingiber officinale var. rubrum Theilade and improving antioxidant and anticancer activity using response surface methodology
    Ghasemzadeh A, Jaafar HZ, Rahmat A
    BMC Complement Altern Med, 2015;15:258.
    PMID: 26223685 DOI: 10.1186/s12906-015-0718-0
    Analysis and extraction of plant matrices are important processes for the development, modernization, and quality control of herbal formulations. Response surface methodology is a collection of statistical and mathematical techniques that are used to optimize the range of variables in various experimental processes to reduce the number of experimental runs, cost , and time, compared to other methods.
    Matched MeSH terms: Catechols/isolation & purification*; Catechols/pharmacology; Catechols/chemistry
  20. Fulltext Variation of the Phytochemical Constituents and Antioxidant Activities of Zingiber officinale var. rubrum Theilade Associated with Different Drying Methods and Polyphenol Oxidase Activity
    Ghasemzadeh A, Jaafar HZ, Rahmat A
    Molecules, 2016 Jun 17;21(6).
    PMID: 27322227 DOI: 10.3390/molecules21060780
    The effects of different drying methods (freeze drying, vacuum oven drying, and shade drying) on the phytochemical constituents associated with the antioxidant activities of Z. officinale var. rubrum Theilade were evaluated to determine the optimal drying process for these rhizomes. Total flavonoid content (TFC), total phenolic content (TPC), and polyphenol oxidase (PPO) activity were measured using the spectrophotometric method. Individual phenolic acids and flavonoids, 6- and 8-gingerol and shogaol were identified by ultra-high performance liquid chromatography method. Ferric reducing antioxidant potential (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays were used for the evaluation of antioxidant activities. The highest reduction in moisture content was observed after freeze drying (82.97%), followed by vacuum oven drying (80.43%) and shade drying (72.65%). The highest TPC, TFC, and 6- and 8-shogaol contents were observed in samples dried by the vacuum oven drying method compared to other drying methods. The highest content of 6- and 8-gingerol was observed after freeze drying, followed by vacuum oven drying and shade drying methods. Fresh samples had the highest PPO activity and lowest content of flavonoid and phenolic acid compounds compared to dried samples. Rhizomes dried by the vacuum oven drying method represent the highest DPPH (52.9%) and FRAP activities (566.5 μM of Fe (II)/g DM), followed by freeze drying (48.3% and 527.1 μM of Fe (II)/g DM, respectively) and shade drying methods (37.64% and 471.8 μM of Fe (II)/g DM, respectively) with IC50 values of 27.2, 29.1, and 34.8 μg/mL, respectively. Negative and significant correlations were observed between PPO and antioxidant activity of rhizomes. Vacuum oven dried rhizomes can be utilized as an ingredient for the development of value-added food products as they contain high contents of phytochemicals with valuable antioxidant potential.
    Matched MeSH terms: Catechols/chemistry
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