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Bratislava, Slovakia

Mucaji P.,Katedra Farmakognozie a Botaniky | Nagy M.,Katedra Farmakognozie a Botaniky | Sersen F.,Comenius University | Svajdlenka E.,Ustav prirodnich leciv | And 3 more authors.
Chemicke Listy

Methanolic extract from leaves of Karwinskia humboldtiana (Schult.) Zucc. was subjected to fractionation with a pair of immiscible solvents and subsequently tested for antioxidant activity. Using DPPH the order of scavenging activities of the extracts in comparison with standards of L-ascorbic acid and quercetin was as follows: ethyl acetate fraction > L-ascorbic acid > quercetin > butan-1-ol > light petrol > chloroform > water. The capability of scavenging OH radicals determined by EPR was as follows: ethyl acetate, chloroform > light petrol > butan-1-ol > water fractions. On the basis of availability and antioxidant activity of these fractions, isolation of constituents from butanol fractions was achieved. Separation of this fraction led to the isolation of (+)-epicatechin and flavonol derivatives - quercetin, quercetin 3-O-glucoside (isoquercitrin), quercetin-3-O-galactoside (hyperosid), quercetin-3-O-ara-binoside, quercetin 3-0-rutinoside (rutin), kaempferol 3-O-arabinoside and kaempferol 3-O-rutinoside. All of them might be responsible for the observed antioxidant effects. Source

Markechova D.,Ustav Analytickej Chemie | Polacek R.,Ustav Analytickej Chemie | Majek P.,Ustav Analytickej Chemie | Sadecka J.,Ustav Analytickej Chemie
Chemicke Listy

The determination has been carried out using excitation- emission matrix fluorescence along with parallel factor analysis (PARAFAC), partial least-squares regression (PLS) and multiple linear regression (MLR). Calibration models consisting of varying spirit composition and brandy were constructed and their accuracy was evaluated through the root-mean-square error of prediction (RMSEP). PLS was a better method compared with MLR due to its lower RMSEP values. The right-angle cell geometry of fluorescence measurements yielded better results than the front-face technique. Source

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