Modeling of the total antioxidant capacity of rooibos (Aspalathus linearis) tea infusions from chromatographic fingerprints and identification of potential antioxidant markers.

Models to predict the total antioxidant capacity (TAC) of rooibos tea infusions from their chromatographic fingerprints and peak table data (content of individual phenolic compounds), obtained using HPLC with diode array detection, were developed in order to identify potential antioxidant markers. Peak table data included the content of 12 compounds, namely phenylpyruvic acid-2-O-glucoside, aspalathin, nothofagin, isoorientin, orientin, ferulic acid, quercetin-3-O-robinobioside, vitexin, hyperoside, rutin, isovitexin and isoquercitrin. The TAC values, measured using the oxygen radical absorbance capacity (ORAC) and DPPH radical scavenging assays, could be predicted from the peak table data or the chromatographic fingerprints (prediction errors 9-12%) using partial least squares (PLS) regression. Prediction models created from samples of only two production years could additionally be used to predict the TAC of samples from another production year (prediction errors<13%) indicating the robustness of the models in a quality control environment. Furthermore, the uninformative variable elimination (UVE)-PLS method was used to identify potential antioxidant markers for rooibos infusions. All individual phenolic compounds that were quantified were selected as informative variables, except vitexin, while UVE-PLS models developed from chromatographic fingerprints indicated additional antioxidant markers, namely (S)-eriodictyol-6-C-glucoside, (R)-eriodictyol-6-C-glucoside, aspalalinin and two unidentified compounds. The potential antioxidant markers should be validated prior to use in quality control of rooibos tea.

A new concept for variance analysis of hyphenated chromatographic data avoiding signal warping.

Analysis of variance of chromatographic data is usually performed on the peak table or on entire chromatograms. These two data forms require signal pretreatment. Peak table requires peak detection, their standards and quantification, and the second form of data organization requires warping of the studied chromatograms to eliminate the observed peak shifts, which occurs due to minor variations in chromatographic conditions. In our study, a new form of data representation well suited for chromatographic data originating from multi-channel detection is proposed. It requires neither warping of chromatograms, nor peak detection. Its principles and performance are demonstrated for a real data set (being a part of a larger research project initiated to characterize the infusion of fermented rooibos herbal tea in terms of phenolic composition and antioxidant activity). As the method of choice for the analysis of data variation, the Multiple Analysis of Variance applied to the pairwise data representation was chosen.

Properties of B16-F10 murine melanoma cells subjected to metabolic stress conditions.

Neoplastic cells which co-form tumors are usually subjected to various stress factors, mainly hypoxia and shortage of nutrient factors. Such cells employ different strategies that permit their survival under such conditions. Experiments in vitro are usually carried out in the presence of 21% oxygen and medium supplemented with 10% FBS. Altering these parameters can approximate the in vivo conditions found within tumor mass. The present paper reports certain properties (especially ability to metastasize) of B16-F10 cells able to grow upon exposure to altered growth conditions (medium supplemented with 0.06% FBS or presence of 1% oxygen for 24 or 72 hours). These properties were compared with those of control cells cultured in the presence of 21% oxygen and in medium supplemented with 10% FBS. Some properties of the cells exposed to medium supplemented with 0.06% FBS differ from those of cells cultured under low oxygenation conditions (ability to form metastases, to migrate, or to express various proteins). Only the partial deprivation of oxygen did increase both the number of migrating cells and the number of metastases formed. Serum deficiency enhanced only the cell ability to metastasize, but not to migrate. It appears that cultured B16-F10 cells employ different adaptation strategies under conditions of oxygen shortage and those of serum deficiency. Under oxygen deprivation, such cells most likely undergo an epithelial-mesenchymal transition, whereas serum deficiency ("starvation"), while increasing the tumorigenicity of B16-F10 cells, does not induce the epithelial-mesenchymal transition.