Anna Gliszczyńska-Świgło

Biphasic modulation of cell proliferation by quercetin at concentrations physiologically relevant in humans

Optimal in vitro conditions regarding quercetin solubility and stability were defined. Using these conditions, the effect of quercetin on proliferation of the colon carcinoma cell lines HCT-116 and HT29 and the mammary adenocarcinoma cell line MCF-7 was investigated. For the colon carcinoma cell lines, at relatively high concentrations, a significant decrease in cell proliferation was observed, providing a basis for claims on the anti-carcinogenic activity of quercetin. However, at lower concentrations, a subtle but significant stimulation of cell proliferation was observed for all cell lines tested. These results point at a dualistic influence of quercetin on cell proliferation that may affect present views on its supposed beneficial anti-proliferative effect.

Simultaneous analysis of riboflavin and aromatic amino acids in beer using fluorescence and multivariate calibration methods

The study demonstrates an application of the front-face fluorescence spectroscopy combined with multivariate regression methods to the analysis of fluorescent beer components. Partial least-squares regressions (PLS1, PLS2, and N-way PLS) were utilized to develop calibration models between synchronous fluorescence spectra and excitation-emission matrices of beers, on one hand, and analytical concentrations of riboflavin and aromatic amino acids, on the other hand. The best results were obtained in the analysis of excitation-emission matrices using the N-way PLS2 method. The respective correlation coefficients, and the values of the root mean-square error of cross-validation (RMSECV), expressed as percentages of the respective mean analytic concentrations, were: 0.963 and 14% for riboflavin, 0.974 and 4% for tryptophan, 0.980 and 4% for tyrosine, and 0.982 and 19% for phenylalanine.

Comparison of UPLC and HPLC methods for determination of vitamin C

Ultra performance liquid chromatography (UPLC) and high-performance liquid chromatography (HPLC) methods for determination of ascorbic acid (AA) and total AA (TAA) contents (as the sum of AA and dehydroascorbic acid (DHAA) after its reduction to AA) in fruit beverages and in pharmaceutical preparations were compared. Both methods are rapid: total time of analysis was 15 and 6 min for HPLC and UPLC methods, respectively. The methods were validated in terms of linearity, instrument precision, limits of detection (LOD) and quantification (LOQ), accuracy and recovery. Intra- and inter-day instrument precisions for fruit juices, expressed as RSD, were 2.2% and 2.4% for HPLC, respectively, and 1.7% and 1.9% for UPLC, respectively. For vitamin C tablets, inter- and intra-day precisions were 0.4% and 0.5%, respectively (HPLC), and 0.5% and 0.3%, respectively (UPLC). Both methods were sensitive: LOD was 0.049 μg/mL for HPLC and 0.024 μg/mL for UPLC while LOQs were 0.149 and 0.073 μg/mL for HPLC and UPLC, respectively. These methods could be useful in the routine qualitative and quantitative analysis of AA or TAA in pharmaceutical preparations or fruit beverages. However, UPLC method is more sensitive, faster and consumes less eluent.

The role of quinone reductase (NQO1) and quinone chemistry in quercetin cytotoxicity.

The effects of quercetin on viability and proliferation of Chinese Hamster Ovary (CHO) cells and CHO cells overexpressing human quinone reductase (CHO+NQO1) were studied to investigate the involvement of the pro-oxidant quinone chemistry of quercetin. The toxicity of menadione was significantly reduced in CHO+NQO1 cells compared to wild-type CHO cells, validating the NQO1-overexpression in the CHO+NQO1 transfectant. Quercetin inhibited the proliferation of wild-type CHO and CHO+NQO1 cells to a similar extent without affecting cell viability, indicating that NQO1 enrichment of CHO cells did not provide increased protection. On the other hand, inhibition of NQO1 in both types of cells by dicoumarol significantly potentiated the inhibitory effect of quercetin on cell proliferation, revealing the role of NQO1 in cellular protection against quercetin. Altogether, these results can be explained by the hypothesis that both wild-type CHO and CHO+NQO1 cells contain sufficient NQO1 activity for optimal protection against the pro-oxidant effect of quercetin on cell proliferation. The results also point at a cellular NQO1 threshold for optimal protection against quercetin. This NQO1 threshold seems to be in the range of NQO1 activities already present in various tissues.

The influence of stereochemistry on the antioxidant properties of catechin epimers

The influence of stereochemistry on the radical scavenging activity of catechins was investigated by studying the effect of pH on the antioxidant properties of catechin epimers. The difference in the pH-dependent Trolox equivalent antioxidant capacity (TEAC) profiles was observed only in case of gallocatechin gallate (GCG) and epigallocatechin gallate (EGCG), indicating the influence of steric structure on the TEAC antioxidant activity of these galloyl moiety-containing catechins. Based on comparison of the pH-dependent TEAC values to theoretically calculated parameters, including homolytic OH bond dissociation energy and ionization potential (IP) as well as theoretically predicted structures of the most stable monoanions of GCG and EGCG, it was concluded that due to steric hindrance in GCG molecule, the IP value of GCG monoanion increases reflecting lower radical scavenging capacity of GCG in comparison with EGCG. It results in the difference in the pH-dependent TEAC profiles of these two catechin epimers at pH above 3.5. This effect does not occur for other pairs of catechin epimers of this study.

Photostability of pitavastatin—A novel HMG-CoA reductase inhibitor

The photostability of pitavastatin, an HMG-CoA reductase inhibitor used in the treatment of hypercholesterolemia, was investigated. The sample solution was exposed to UV-A radiation and the photodegradation process was monitored by means of spectrophotometric method and HPLC-DAD. Pitavastatin was shown to be photolabile and its photodegradation reaction followed the first-order kinetics with the rate constant k=3.54 x 10(-4)+/-9.43 x 10(-6)s(-1). The chromatograms revealed the presence of four major photoproducts (PP-1-PP-4). The separated and isolated photolytic products were identified using a mass spectrometer coupled with a time of flight (TOF) analyzer. The main reaction observed during exposure to radiation of pitavastatin was photocyclisation leading to formation of four-ring photoproducts.

Influence of the interactions between tea (Camellia sinensis) extracts and ascorbic acid on their antioxidant activity: analysis with interaction indexes and isobolograms.

Products containing natural additives, including antioxidants, are usually perceived by consumers as safer than those with synthetic ones. Natural antioxidants, besides having a preservative activity, may exert beneficial health effects. Interactions between antioxidants may significantly change their antioxidant activity, thus in designing functional foods or food/cosmetic ingredients knowledge about the type of interactions could be useful. In the present study, the interactions between ascorbic acid (AA; vitamin C) and different black and green tea extracts and the influence on their antioxidant activities were investigated. The antioxidant activities of tea extracts and their mixtures with AA prepared in several different weight ratios were measured using the trolox equivalent antioxidant capacity (TEAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and ferric-reducing antioxidant power (FRAP) methods. The type of interaction was determined by interaction indexes and isobolograms. It was found that the weight ratio of extracts to AA significantly influenced the antioxidant activity of a mixture and the type of interaction between these components. The weight ratio of tea extract to AA can cause the change of interaction, e.g. from antagonism to additivism or from additivism to synergism. The observed differences in the type of interactions were probably also a result of different extracts’ polyphenol composition and content. The type of interaction may also be affected by the medium in which extracts and AA interact, especially its pH and the solvent used. To obtain the best antioxidant effect, all these factors should be taken into account during the design of a tea extract–AA mixture. Graphical Abstract

Green tea extract as an anti-browning agent for cloudy apple juice.

BACKGROUND Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L-1 , 2 g L-1 and 3 g L-1 on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A420 ). RESULTS All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L-1 , 2 g L-1 and 3 g L-1 tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L-1 , 2 g L-1 and 3 g L-1 inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice. CONCLUSION Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices.

Chemometric analysis of minerals in gluten-free products: Chemometric analysis of minerals

BACKGROUND Numerous studies indicate mineral deficiencies in people on a gluten-free (GF) diet. These deficiencies may indicate that GF products are a less valuable source of minerals than gluten-containing products. In the study, the nutritional quality of 50 GF products is discussed taking into account the nutritional requirements for minerals expressed as percentage of recommended daily allowance (%RDA) or percentage of adequate intake (%AI) for a model celiac patient. Elements analyzed were calcium, potassium, magnesium, sodium, copper, iron, manganese, and zinc. Analysis of %RDA or %AI was performed using principal component analysis (PCA) and hierarchical cluster analysis (HCA). RESULTS Using PCA, the differentiation between products based on rice, corn, potato, GF wheat starch and based on buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn was possible. In the HCA, four clusters were created. The main criterion determining the adherence of the sample to the cluster was the content of all minerals included to HCA (K, Mg, Cu, Fe, Mn); however, only the Mn content differentiated four formed groups. CONCLUSION GF products made of buckwheat, chickpea, millet, oats, amaranth, teff, quinoa, chestnut, and acorn are better source of minerals than based on other GF raw materials, what was confirmed by PCA and HCA.

Fourier-transform near infrared spectroscopy and chemometrics for discrimination of cold-pressed oils and determination of their chemical parameters

Principal component analysis was performed to discriminate commercial cold-pressed cosmetic oils based on their Fourier-transform near infrared spectroscopy spectra and chemical parameters such as the composition of fatty acids, content of tocopherols, total carotenoids, polyphenols, and chlorophylls, as well as calculated oxidizability and iodine values. It was found that the oils analyzed differed significantly in the chemical composition. The level of total unsaturated fatty acids ranged from 74.0 to 93.4%. The content of carotenoids in oils ranged from 3.1 to 197.1 mg/kg, total chlorophylls from 0.04 to 46.3 mg/kg, and total phenolics from 36 to 596 mg/kg. The oils tested differed also in the content of tocopherols (from 11 to 3836 mg/kg). Principal component analysis based on Fourier-transform near infrared spectroscopy spectra revealed a different pattern of discrimination of the oils compared to principal component analysis based on the chemical parameters. However, using partial least squares regression, good correlations were found between Fourier-transform near infrared spectroscopy spectra and the contribution of linoleic acid (18:2), monounsaturated fatty acids, polyunsaturated fatty acids, unsaturated fatty acids, calculated oxidizability, or calculated iodine values. Good models with coefficients of determination not lower than 0.989 and with low root-mean-square error for cross-validation were obtained when the range from 4800 to 4500 cm−1 was applied. Values of residual predictive deviation for these models were higher than 3.0 indicating very good prediction accuracy. The models obtained were successfully used to predict these parameters for new selected oils.