Simultaneous quantification of six flavonoids in four Scutellaria taxa by HPLC-DAD method

Abstract The objective of this study was to develop and validate a new HPLC method to quantify several flavonoids in the methanol extract prepared from the aerial parts of four Scutellaria L. taxa from flora of Turkey. A simple, sensitive and precise reversed phase HPLC-DAD method was developed and validated for simultaneous determination of six main flavonoids; scutellarein 7-O-β-d-glucopyranoside, hispidulin 7-O-β-d-glucuronopyranoside, apigenin 7-O-β-d-glucopyranoside, hispidulin 7-O-β-d-glucopyranoside, luteolin and apigenin. All standard compounds showed a good linearity (R 2 > 0.999) in a relatively wide concentration range (1-120 µg/ml). The limit of detection of the compounds was in the range of 0.016-1.883 µg/ml and the limit of quantification was in the range of 0.232-3.368 µg/ml. The recoveries of the selected compounds were calculated in the range of 92.20-107.93%. The amounts of flavonoids showed variation in the extracts. The developed method was found to be accurate, precise, reproducible, and can be successfully applied to identify and quantify the flavonoid composition of Scutellaria species.

The cysteine releasing pattern of some antioxidant thiazolidine-4-carboxylic acids.

Oxidative stress that corresponds to a significant increase in free radical concentration in cells can cause considerable damage to crucial biological macromolecules if not prevented by cellular defense mechanisms. The low-molecular-weight thiol glutathione (GSH) constitutes one of the main intracellular antioxidants. It is synthesized via cysteine, an amino acid found only in limited amounts in cells because of its neurotoxicity. Thus, to ensure an efficient GSH synthesis in case of an oxidative stress, cysteine should be provided extracellularly. Yet, given its nucleophilic properties and its rapid conversion into cystine, its corresponding disulfide, cysteine presents some toxicity and therefore is usually supplemented in a prodrug approach. Here, some thiazolidine-4-carboxylic acids were synthesized and evaluated for their antioxidant properties via the DDPH and CUPRAC assays. Then, the cysteine releasing capacity of the obtained compounds was investigated in aqueous and organic medium in order to correlate the relevant antioxidant properties of the molecules with their cysteine releasing pattern. As a result, the structures' antioxidative properties were not only attributed to cysteine release but also to the thiazolidine cycle itself.

Effect of in vitro gastrointestinal digestion on the bioavailability of phenolic components and the antioxidant potentials of some Turkish fruit wines.

This study was designed to evaluate the effects of in vitro gastrointestinal simulation method on the antioxidant potentials and phenolic profile of some Turkish fruit wines and to compare the results with a Turkish red wine prepared from native grape varieties (Papazkarasi). For this purpose, blueberry, black mulberry and cherry wines were studied since they are widely consumed in Turkey. Papazkarasi wine was chosen due to the lack of studies regarding this type of wine. Antioxidant potentials of samples were measured with four different methods: DPPH radical-scavenging activity, H2O2-scavenging activity, cupric reducing capacity and total antioxidant capacity assays. The phenolic profiles of samples were evaluated by the determination of total phenolic content and HPLC-DAD analysis of seven different molecules. The results of this study provided information not only the effect of gastrointestinal digestion on parameters mentioned above, but also the bioaccessibility about the phenolic compounds found in these four different wine samples.