Wyniki wyszukiwania - Biblioteka Nauki

1

Determination of catechin forms in black tea using isocratic elution HLPC system

100%

Smiechowska M. , Dmowski P.

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tom 50

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nr 3-4

EN

In this paper the content of catechins in black fermented tea, imported to Poland by sea from China, India, Indonesia, Kenya, Malawi and Vietnam, was determined. The material was collected directly from ship cargo holds. An isocratic elution system was applied for the separation of catechins in tea. Extracts were prepared from tea samples and analysed for catechin content by HPLC. Catechin identification from chromatograms of examined tea extracts was performed by comparison of retention times with respective standards purchased from Sigma Aldrich. Chromatographic analysis by HPLC shows that examined tea contained (-)-(EGCG) in highest quantities, ranging from 148.9-292.3 mg/l, as proved by comparative analysis with a chromatogram of catechin standards, based on their retention times. Only Chinese tea contained more (-)-(EGC) - 266.2, and (-)-(EC) - 193.6, than (-)-(EGCG) - 148.9 mg/l.

PL

W pracy oznaczono zawartość katechin w herbatach czarnych fermentowanych, importowanych do Polski drogą morską z Chin, Indii, Indonezji, Kenii, Malawi i Wietnamu. Próbki herbat pobierano bezpośrednio z ładowni statków. W metodyce do rozdziału katechin w herbacie wykorzystano system elucji izokratycznej. Z próbek herbat przygotowano ekstrakty i analizowano katechiny metodą HPLC. Identyfikację katechin przeprowadzono, porównując ich czasy retencji z wzorcami katechin Sigma Aldrich. Analiza chromatograficzna HPLC wykazała, że badane herbaty w największej ilości zawierały (-) - (EGCG), od 148,9 do 292,3 mg/l, co potwierdzono analizą porównawczą z chromatogramem wzorców katechin na podstawie ich czasów retencji. Jedynie herbata chińska zawierała więcej (-) - (EGC) - 266,2 mg/l - oraz (-) - (EC) - 193,6 mg/l - aniżeli (-) - (EGCC.) - 148,9 mg/l.

2

HPLC analysis of catechins from Camelia spp.

86%

Sempruch C. , Stefaniuk A. , Chrzanowski G. , Leszczynski B.

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tom 61

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nr Suppl.1

3

The radical scavenging capacity of green tea

86%

Muzolf M. , Gliszczynska-Swiglo A. , Tyrakowska B.

Polish Journal of Natural Sciences. Supplement

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2007

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tom 04

63-69

4

Comparison of methods for determining the content and polymerization of proanthocyanidins and catechins

86%

Oszmianski J. , Bourzeix M.

Polish Journal of Food and Nutrition Sciences

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1996

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tom 05

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nr 2

EN

The methods with vanillin (V), Folin-Ciocalteau (FC) or dimethyla- minocinnamaldehyde (DC) reagent and spectometric method at 280 nm (A) for determining the content of proanthocyanidins and catechins and their polymerization degree were compared. The (+) catechin, (-)epicatechin and their dimer and trimer standards, and grape wine, wine concentrate and powdered wine were examined. The DC reagent appeared most sensitive in the catechin and proanthocyanidin analysis with the molar absorption values for catechins being 55-fold higher than for the FC reagent In the proanthocyanidin analysis with the DC reagent the use of catechin standard curve is not recommended for the determination of proanthocyanidin content because the concentrations of 0.5 g/L for dimers and 0.3 g/L for trimers were obtained instead of 1 g/L in model solutions. Hie V/DC value approximated most closely the real values of proanthocyanidin polymerization.

PL

W pracy porównano cztery metody (z odczynnikiem Folina-Ciocalteu, wanilinowym, aldehydem dimetyloaminocynamonowym i metodę spektrofotometryczną przy 280 nm) oznaczania katechin i proantocyjanidyn oraz ich stopnia kondensacji w roztworach modelowych standardów: (+)katechiny i jej dimeru procyjanidyny B3, trimeru C2 oraz (-) epikatechiny i jej dimeru B2 i trimeru C1. Do oznaczeń stosowano uprzednio przygotowane standardy dimerów i trimerów procyjanidyn oraz próbki wina gronowego, jego koncentratu i suszu . Stwierdzono, że najbardziej czułym odczynnikiem w analizach katechin i proantocyjanidyn jest aldehyd dimetyloaminocynamonowy. Absorbancja molowa katechin z tym odczynnikiem była 55-krotnie wyższa niż z odczynnikiem Folina-Ciocalteu (Tabela 1). W oznaczeniach proantocyjanidyn z aldehydem dimetyloaminocynamonowym nie należy obliczać wyników z krzywej wzorcowej katechin, gdyż dla roztworów modelowych zamiast stężenia 1 g/L uzyskano 0.5 g/L dla dimerów i 0.3 g/L dla trimerów (Tabela 2). Najbardziej zbliżone do rzeczywistych informacje o stopniu kondensacji proantocyjanidyn wyraża stosunek oznaczenia metodą z odczynnikiem wanilinowym do oznaczenia z aldehydem dimetyloaminocynamonowym. Wyniki badań w roztworach modelowych na standardach przetestowano na próbkach wina, jego koncentratu i suszu (Rysunek 1 i 2).

5

Clinical relevance of the inhibitory effect of green tea catechins [GTCs] on prostate cancer progression in combination with molecular profiling of catechin-resistant tumors: an integrated view

86%

Bettuzzi S. , Rizzi F. , Belloni L.

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tom 10

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nr 1

EN

Prostate cancer (CaP) is a fast-growing health and social problem already representing the second leading cause of cancer-related death among men in Western countries. Lifestyle-related factors and diet are major contributors for CaP promotion. Because of unfavourable prognosis of extra-prostatic CaP, prevention is considered the best approach to fight it at present time. Green Tea Catechins (GTCs) were proven effective at inhibiting cancer growth in several laboratory studies. We recently performed a pilot clinical trial in HG-PIN subjects showing that only 1/30 tumour was diagnosed in subjects treated for 1 year with 600 mg/die GTCs, while 9/30 cancers were found in placebo-treated men. CaP is an elusive disease, whose biological behaviour is difficult to predict. We have recently described and validated a RT-qPCR method based on a 8-genes signature that significantly discriminated benign tissue from CaP in both humans and TRAMP mice spontaneously developing CaP. In the animal model, also GTCs-resistant CaP was significantly discriminated from GTCs-sensitive CaP, i.e. responding to GTCs administration. Preliminary experiments in our laboratory have shown that this method can be successfully applied to a single tissue needle biopsy specimen in humans. The combination of these results may be of particular significance on the field. In fact, GTCs treatment for men at high risk of CaP as first line prevention therapy in combination with the 8-genes signature profiling in tissue needle biopsies for real time monitoring of patient's response might importantly change, in the near future, the clinical managing of this highly diffuse malignancy.

6

Molecular targets of [-]-epigallocatechin-3-gallate [EGCG]: specificity and interaction with membrane lipid rafts

72%

Patra S. K. , Rizzi F. , Silva A. , Rugina D. O. , Bettuzzi S.

Journal of Physiology and Pharmacology. Supplement

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2008

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tom 59

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nr 9

217-235

7

Antioxidant properties of acetone extracts from selected fresh and dried spices

72%

Druzynska B. , Wojda M.

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nr 2[A]

47-51

EN

The purpose of the study was to determine antioxidant properties of acetone extracts from selected fresh and dried spices. Three spices have been examined: garlic, oregano and rosemary. Preparations were obtained by the extraction of polyphenols with a 70% acetone solution. The contents of total polyphenols and total catechin were determined in the study. The ability of total polyphenols contained in the obtained extracts to chelate Fe(II) ions was examined, too. The antioxidant properties of the examined extracts were assayed with three methods: against stable, synthetic DPPH radicals, cation-radicals ABTS and against hydroxyl radicals. On the basis of findings it turned out that condensed tannins are a dominant group of polyphenols in oregano, rosemary and fresh garlic. Granular garlic contained a higher level of catechins than tannins. All preparations of fresh spices dispalyed the ability to chelate iron ions. All extracts had antioxidant properties against synthetic radicals, with the exception of garlic preparation which did not inhibit hydroxyl radicals. Extracts of fresh spices demonstrated better antioxidant properties.

PL

Celem pracy było oznaczenie zawartości polifenoli i ich właściwości przeciwutleniających w wybranych przyprawach (czosnek, rozmaryn oregano). W acetonowych ekstraktach przypraw oznaczono zawartość polifenoli ogółem i tanin skondensowanych. Oznaczono zdolność polifenoli zawartych w ekstraktach do chelatowania jonów Fe(II ). Właściwości przeciwutleniające zbadano metodami z wykorzystaniem rodników DPPH• i kationorodników ABTS•+ oraz metodą spektrofluorymetryczną wobec rodników hydroksylowych. Na podstawie otrzymanych wyników stwierdzono, że dominującą grupą polifenoli w oregano, rozmarynie i czosnku świeżym były taniny skondensowane. Preparaty z przypraw świeżych wykazywały zdolność do chelatowania jonów żelaza (II ). Wszystkie ekstrakty wykazywały właściwości przeciwutleniające wobec syntetycznych rodników, z wyjątkiem preparatu z czosnku, który nie inhibował rodników hydroksylowych. Lepsze właściwości przeciwutleniające wykazywały ekstrakty z przypraw świeżych.

8

Rapid high performance thin layer chromatographic method for quantitation of catechin from extracts of cashew leaves - a short report

72%

Jaiswal Y. , Tatke P. , Gabhe S. , Vaidya A.

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tom 63

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nr 1

EN

Cashew is a tropical tree with immense commercial value and the use of its various parts in the confectionary, food, herbal and tanning industry has gained tremendous importance. Thus, the development of quality control method for routine analysis of various products of this widely used plant would be a great help to analysts. The phytochemistry of this plant has not been explored in detail. Anacardium occidentale Linn. (cashew) is reported to contain many antioxidant and polyphenolic compounds. However, there have been no reports published for the HPTLC analysis of the extracts of cashew leaves. Hence, an attempt has been made to develop a HPTLC method for estimation of catechin from leaf extracts. The present paper reveals a rapid high performance thin layer chromatographic method developed for quantitation of catechin from extracts of cashew leaves. The chromatographic parameters such as solvent system, development time, saturation time, detection wavelength were optimized. The mobile phase toluene: ethyl acetate: methanol: formic acid (6:6:1:0.1v/v/v/v) gave the best resolution for various components. The separation of various components and quantitation of amount of catechin was successfully carried out from extracts of cashew leaves. The aqueous extract of leaves contained a higher amount of catechin as compared to ethanol extract. The presence of tannins and phenolics was visualised as bluish-black bands with 5% alcoholic FeCl3 as visualising agent. The method can prove to be a rapid, sensitive and economic alternative as compared to other chromatographic methods especially HPLC for detection of catechin in various food products and herbal formulations.

9

Anti-nutritive and anti-allergic properties of green tea extract depend on catechins concentration and processing

72%

Velickovic T. C. , Tantoush Z. , Kravic B. , Mihajlovic L. , Apostolovic D. , Atanaskovic-Markovic M. , Stanic-Vucinic D.

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tom 61

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nr Suppl.1

10

Simultaneous determination of gallic acid, protocatechuic acid, catechin, epicatechin, quercetin and kaempferol in Chinese chestnut (Castanea mollissima blume) kernel by high-performance liquid chromatography with diode array detection

72%

Wang T. , Yang Y. D. , Du B. , Yu S. , Hou W. L.

Acta Chromatographica

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2014

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tom Vol. 26, no. 3

539--550

EN

Chestnut exhibits anti-inflammatory, styptic, anti-diarrhea, and analgestic effects as a traditional Chinese medicine. There is increasing evidence that shows that the consumption of chestnuts has become more important in human nutrition due to the health benefits provided by the antioxidants. The phenolic compounds are responsible for major bioactivities, such as anti-tumor and anti-oxidation. A high-performance liquid chromatography (HPLC) method with diode array detection (DAD) was established for the simultaneous determination of six phenolic compounds (gallic acid, GA; protocatechuic acid, PR; catechin, CA; epicatechin, EP; quercetin, QU; kaempferol, KA) in Chinese chestnut (Castanea mollissima blume) kernel. The sample followed by separation on Eclipse XDB-C18 column (150 × 4.6 mm, id., 5 μm) with gradient elution of methanol-1.0% acetate acid solution as a mobile phase, at a temperature of 30°C, under the ratio of 1.2 mL min-1, with 5 μL injection volume, and multi-wavelength synthesis was used with DAD. The correlation coefficients were larger than 0.999, the recoveries were 97.58% for GA, 100.41% for PA, 96.23% for CA, 101.38% for QU, 99.15% for EP, and 98.60% for KA, relative standard deviation (RSD) were 1.04% for GA, 1.21% for PA, 1.09% for CA, 1.19% for QU, 1.06% for EP, and 1.20% for KA. This method was applied for the determination of phenolics in chestnut kernel and was found to be fast, sensitive, and suitable.

11

High pressure-modified starches as carriers for phenolic compounds

72%

Gorecki A. R. , Blaszczak W. , Hernandez T. , Estrella I. , Bartolome B. , Garrido L.

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tom 61

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nr Suppl.1

12

Gastroprotective and cicatrizing activity of the Ziziphus joazeiro Mart. leaf hydroalcoholic extract

58%

Brito S. M. O. , Martins A. O. B. P. B. , De Oliveira M. R. C. , Vidal C. S. , De Lacerda Neto L. J. , Ramos A. G. B. , Da Gruz L. P. , Nascimento E. A. , Da Costa J. G. M. , Coutinho H. D. M. , Quintans-Junior L. J. , De Menezes I. R. A.

Journal of Physiology and Pharmacology

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2020

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tom 71

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nr 3

13

Antyoksydacyjne wlasciwosci zielonej herbaty

58%

Ostrowska J. , Stankiewicz A. , Skrzydlewska E.

Bromatologia i Chemia Toksykologiczna

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2001

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tom 34

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nr 2

131-140

14

The inhibitory effect of polyphenols on human gut microbiota

58%

Duda-Chodak A.

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2012

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tom 63

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nr 5

15

Metabolism of phenolic compounds in Vitis riparia seeds during stratification and during germination under optimal and low temperature stress conditions

58%

Wrobel M. , Karamac M. , Amarowicz R. , Fraczek E. , Weidner S.

Acta Physiologiae Plantarum

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2005

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tom 27

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nr 3A

PL

We studied the alterations in phenolic compounds in grape seeds during their stratification and germination under optimal conditions (+25 °C) and at low temperature (+10 °C). Biological materials in the study were seeds of Vitis riparia. Phenolic compounds were extracted from defatted seeds using 80 % methanol or 80 % acetone. The content of total phenolics was determined with the Folin-Ciocalteau reagent, while the content of tannins was determined by vanillin assay and the protein (BSA) precipitation method. The RP - HPLC method was used to determine phenolic compounds (phenolic acids, catechins) in the extracts. High amounts of tannins, catechins, gallic acid and lesser amounts of p-coumaric acid were found in the seeds. The content of total phenolics in acetone extracts was higher than that obtained using methanol. The amounts of phenolic acids and tannins found in V. riparia seeds after stratification were much lower. It may confirm a possible role of these compounds in dormancy of V. riparia seeds. After 72 h of low temperature treatment, inhibition of grape root growth and biochemical changes in seeds were detected. The chilling stimulated increased accumulation of some phenolic compounds (free gallic acid and catechins) in the seeds. These substances can protect plants against some abiotic stressors.

16

Enzymatic oxidation of polyphenols in fruit products and model solutions

58%

Los J. , Wilska-Jeszka J. , Pawlak M.

Polish Journal of Food and Nutrition Sciences

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1996

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tom 05

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nr 1

EN

Polyphenoloxidase (PPO) activity, total polyphenols and flavanols contents in various fruit species were investigated in relation to their susceptibility to browning processes. Marked differences in substrate affinities of PPO preparations from apples and pears were found. The rate of browning of (+)catechin solutions was higher for the apple PPO than for the pear enzyme. In contrast, the pear PPO catalysed an oxidation of (-)epicatechin to higher extent. Phenolic acids, i.e. chlorogenic and caffeic, were oxidised more slowly than catechins. It was observed that in pulps from fruits rich in polyphenoloxidase, e.g. from apples and pears, stored at room temperature, the browning process was accompanied by considerable losses of flavanols (40% after 1 h). In strawberry pulps exhibiting a low PPO activity no decrease of flavanols was observed under the same conditions.

PL

Prowadzono badania aktywności polifenolooksydazy (PPO) oraz zawartości związków flawanolowych w różnych gatunkach owoców pod kątem ich podatności na procesy brunatnienia. Stwierdzono duże zróżnicowanie zarówno zawartości PPO jak i związków fenolowych w zależności od gatunku i odmiany. Owoce o niższej kwasowości (pH około 4), np. gruszki i niektóre odmiany jabłek, odznaczały się wysoką aktywnością PPO. Owoce pigwowca, charakteryzujące się wysoką kwasowością (pH = 2,7) i bardzo niską aktywnością PPO, zawierały najwięcej flawanoli — 2,2 g/kg, czyli 3-krotnie więcej niż jabłka odmiany Jonathan. Dane te przedstawiono w tabeli 1. Określono stopień powinowactwa substratowego preparatów polifenolooksydaz wyizolowanych z jabłek i gruszek. Stwierdzono, że proces brunatnienia przebiegał szybciej w roztworach katechin niż kwasów fenolowych, przy czym w obecności preparatu PPO z gruszek szybciej utleniała się (-)epikatechina, natomiast dla PPO z jabłek lepszym substratem była (+)katechina (rys.1). Kontrolując szybkość brunatnienia oraz zmiany zawartości flawanoli w miazgach i sokach z jabłek, gruszek i truskawek, stwierdzono, że w produktach z owoców o wysokiej aktywności polifenolooksydaz, intensywnemu brunatnieniu towarzyszył szybki spadek zawartości flawanoli, np. w sokach jednocześnie ogrzewanych i napowietrzanych straty flawanoli po 3 godzinach sięgały 60% (rys. 4). Przeprowadzenie chromatografii na żelu Sephadex LH-20 pozwoliło stwierdzić, że głównym kierunkiem oksydatywnych przemian związków fenolowych jest ich polimeryzacja — spadek zawartości monomerów i oligomerów oraz wzrost ilości średniocząsteczkowych polimerów (rys. 3).

17

Intracellular reduced glutathione content in normal and type 2 diabetic erythrocytes: effect of insulin and (-)epicatechin

58%

Rizvi S. I. , Zaid M. A.

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2001

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tom 52

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nr 3

18

Zmiany aktywnosci antyoksydacyjnej [plus] katechiny w wyniku utleniania enzymatycznego

51%

Sosnowska D.

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nr 3

69-76

PL

(+) katechina wykazuje cenne właściwości biologiczne, jest efektywnym zmiataczem wolnych rodników. W pracy badano wpływ enzymatycznego utleniania (+) katechiny na jej aktywność anty oksydacyjną. Proces utleniania (+) katechiny prowadzono przy udziale polifenolooksydazy (PPO) i tyrozynazy w pH 4 i 7. Aktywność anty oksydacyjną badanych roztworów określano dwoma metodami polegającymi na zmiataniu rodników: DPPH i ABTS. Zmiany zawartości (+) katechiny oraz produkty jej degradacji rejestrowano metodą HPLC i TLC. Szybkość utleniania (+) katechiny była wyższa w obecności PPO niż tyrozynazy. Obniżenie pH środowiska reakcyjnego z 7 do 4 powodowało zmniejszenie szybkości utleniania katechiny. Dwugodzinne utlenianie katechiny (PPO w pH 7) powodowało spadek zawartości tego monomeru o 57% i pojawienie się dimerów i tetramerów. Natomiast efektywność zmiatania stabilnego rodnika DPPH obniżyła się o 25% a ABTS tylko o 12%, co może sugerować, że produkty enzymatycznego utleniania (+) katechiny wykazują pewną aktywność anty oksydacyjną w stosunku do tych rodników.

EN

The effect of enzymatic oxidation of (+) catechin on its antioxidant activity was investigated. Enzymatic oxidation of (+) catechin in the presence of apple polyphenol oxidase (PPO) and tyrosinase was studied at 25°C and in solution at pH 4 and 7. The antioxidant activity was determined by two methods: ABTS and DPPH radical scavenging. (+) Catechin and the reaction products were monitored by HPLC and TLC. The rate of reaction in the presence of PPO at pH 7 was higher than at pH 4. The reaction products of catechin oxidation were dimers and tetramers. The rate of oxidation of catechin in the presence of tyrosinase was slower than in the presence of PPO. Antioxidant activity of catechin after two hours oxidation (PPO at pH 7) was reduced about 25% in DPPH method (expressed as IC50) and only about 12% in ABTS method (expressed as TEAC), in spite of big decrease content of monomer catechin (57%). This finding indicates that as a result of (+) catechin enzymatic oxidation the compounds with antioxidant activity are formed.

19

Porownanie wlasciwosci antyoksydacyjnych czarnej i zielonej herbaty

51%

Ostrowska J. , Luczaj W. , Skrzydlewska E.

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tom 38

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nr 3

211-221

20

Antioxidant activity of different kinds of commercially available teas – diversity and changes during storage

51%