15416-77-0

Sodium periodate oxidation of caffeic acid was investigated in aqueous solutions with pH ranging from 2 to 7.Products formed from quinone evolution were monitored by HPLC.It was found that they were affected both qualitatively and quantitatively by the conditions of the reaction.The rate and yield of the reaction increased with the pH.In particular, two products obtained at pH values lower than 4.6 approximately, were analysed by reverse phase HPLC.By using 1H and 13C NMR and mass spectrometries, these compounds were shown to be two stereoisomers of 2,5-(3',4'-dihydroxyphenyl)tetrahydrofuran 3,4-dicarboxylic acid.

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Hepatocellular carcinoma (HCC) is among the most aggressive and fatal cancers. Its treatment with conventional chemotherapeutic agents is inefficient, due to several side effects linked to impaired organ function typical of liver diseases. Consequently, there exists a decisive requirement to explore possible alternative chemopreventive and therapeutic strategies. The use of dietary antioxidants and micronutrients has been proposed for HCC successful management. The aim of this work was to test in vitro the effects of lipoic acid, caffeic acid and a new synthesized lipoylcaffeic conjugate on human hepatoma cell lines in order to assess their effect on tumor cell growth. The results of cytotoxicity assays at different times showed that the cell viability was directly proportional to the molecule concentrations and incubation times. Moreover, to evaluate the pro- or anti-inflammatory effects of these molecules, the cytokine concentrations were evaluated in treated and untreated cellular supernatants. The obtained cytokine pattern showed that, at the increasing of three molecules concentrations, three pro-inflammatory cytokines such as IL-1α, IL-8 and TNF-α decreased whereas the antiinflammatory cytokine such as IL-10 increased.

Yam tubers could serve as a cost-effective source of tyrosinase for various applications. Here a novel but cheap method of purification, and some properties of the enzyme from four species of yam tubers having high tyrosinase activity are described. The native and subunit molecular weights of each of the purified tyrosinase were between 41-58 kDa and 24-27 kDa respectively. Optimum pH and temperature were 6.5 and 50 C respectively. Tyrosinase from tubers of Colocasia esculenta retained more than 50% activity in ethanol (≤&60%). All the purified enzymes were activated in 40% ether by between 120 and 170%, and maintained 100% residual activity at up to 65% ether for 17 h. Both the K;bsubesub & and V;bsubesub & increased in 40% ether, leading to a corresponding increase in k;bsubesubbsubesub &. All the enzymes had both monophenolase and diphenolase activities. β- Mercaptoethanol and to a lesser extent, glutathione were good inhibitors. In aqueous systems, the purified tyrosinase catalyzed formation of coloured products in the presence of some substrates such as catechol, pyruvic acid and ammonia. The catalytic properties of these enzymes especially in organic solvents suggest that they may find uses in some biotechnological applications.

Different mechanisms for inhibiting tyrosinase can be designed to avoid postharvest quality losses of fruits and vegetables. The action of tyrosinase on caffeic acid and its n-nonyl ester (n-nonyl caffeate) was characterized kinetically in this work. The

The electrochemical oxidation of catechols leads to the formation of o-benzoquinones. This property has been applied to effectively synthesize α-arylated products of α-oxoketene N,N-acetals with a tetrahydropyrimidine ring.

Polyphenol oxidase (E.C. 1.14.18.1) (PPO) extracted from yacon roots (Smallanthus sonchifolius) was partially purified by ammonium sulfate fractionation and separation on Sephadex G-100. The enzyme had a molecular weight of 45 490 ± 3500 Da and Km/s

Polyphenol oxidase (PPO) from eggplant was extracted and partially purified by a two-step fractionation-precipitation using ammonium sulfate and phenylsepharose hydrophobic interaction chromatography. The eggplant PPO extract was characterized concerning

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