Calibration transfer between NIR instruments using optimally predictive calibration subsets.

In this study, a new approach for the selection of informative standardization samples from the original calibration set for the transfer of a calibration model between NIR instruments is proposed and evaluated. First, a calibration model is developed, after variable selection by the Final Complexity Adapted Models (FCAM) method, using the significance of the PLS regression coefficients (FCAM-SIG) as selection criterion. Then, the resulting model is used for the selection of the best fitting subset of calibration samples with optimally predictive ability, called the optimally predictive calibration subset (OPCS). Next, the standardization samples are selected from the OPCS. The spectra on the slave instruments are transferred to corresponding spectra on the master instrument by the widely used Piecewise Direct Standardization (PDS) method. Thereafter, for the test set on the slave instrument, a 3D response surface plot is drawn for the root mean squared error of prediction (RMSEP) as a function of the number of OPCS samples and window sizes used for the PDS method. Finally, the smallest set of calibration samples, in combination with the optimal window size, providing the optimal RMSEP, is selected as standardization set. The proposed OPCS approach for the selection of standardization samples is tested on two real-life NIR data sets providing 13 X-y combinations to model. The results show that the obtained numbers of OPCS-based standardization samples are statistically significantly lower than those obtained with the widely used representative sample selection method of Kennard and Stone, while the predictive performances are similar.

Quality Control and Authentication of Argan Oils: Application of Advanced Analytical Techniques.

In addition to the nutritional and therapeutic benefits, Argan oil is praised for its unique bio-ecological and botanic interest. It has been used for centuries to treat cardiovascular issues, diabetes, and skin infections, as well as for its anti-inflammatory and antiproliferative properties. Argan oil is widely commercialized as a result of these characteristics. However, falsifiers deliberately blend Argan oil with cheaper vegetable oils to make economic profits. This reduces the quality and might result in health issues for consumers. Analytical techniques that are rapid, precise, and accurate are employed to monitor its quality, safety, and authenticity. This review provides a comprehensive overview of studies on the quality assessment of Moroccan Argan oil using both untargeted and targeted approaches. To extract relevant information on quality and adulteration, the analytical data are coupled with chemometric techniques.

Evaluation of Multivariate Filters on Vibrational Spectroscopic Fingerprints for the PLS-DA and SIMCA Classification of Argan Oils from Four Moroccan Regions.

This study aimed to develop an analytical method to determine the geographical origin of Moroccan Argan oil through near-infrared (NIR) or mid-infrared (MIR) spectroscopic fingerprints. However, the classification may be problematic due to the spectral similarity of the components in the samples. Therefore, unsupervised and supervised classification methods-including principal component analysis (PCA), Partial Least Squares-Discriminant Analysis (PLS-DA) and Soft Independent Modeling of Class Analogy (SIMCA)-were evaluated to distinguish between Argan oils from four regions. The spectra of 93 samples were acquired and preprocessed using both standard preprocessing methods and multivariate filters, such as External Parameter Orthogonalization, Generalized Least Squares Weighting and Orthogonal Signal Correction, to improve the models. Their accuracy, precision, sensitivity, and selectivity were used to evaluate the performance of the models. SIMCA and PLS-DA models generated after standard preprocessing failed to correctly classify all samples. However, successful models were produced after using multivariate filters. The NIR and MIR classification models show an equivalent accuracy. The PLS-DA models outperformed the SIMCA with 100% accuracy, specificity, sensitivity and precision. In conclusion, the studied multivariate filters are applicable on the spectroscopic fingerprints to geographically identify the Argan oils in routine monitoring, significantly reducing analysis costs and time.

Development of a capillary electrophoresis method for the separation of flavonolignans in silymarin complex.

CE method for the baseline separation of structurally similar flavonolignans silybin A, silybin B, isosilybin A, isosilybin B, silychristin, silydianin, and their precursor taxifolin in silymarin complex has been developed and validated. The optimized background electrolyte was 100 mmol/L boric acid (pH 9.0) containing 5 mmol/L heptakis(2,3,6-tri-O-methyl)-ß-CD and 10% (v/v) of methanol. The separation was carried out in an 80.5/72 cm (50 µm id) fused silica capillary at +25 kV with UV detection at 200 nm. Genistein (10 µg/mL) was used as internal standard. The resolution between the diastereomers of silybin and isosilybin was 1.73 and 2.59, respectively. The method was validated for each analyte in a concentration range of 2.5-50 µg/mL. The calibration curves were rectilinear with correlation coefficients ≥0.9972. The method was applied to determine flavonolignans in two dietary supplements containing Silybum marianum extract. The accuracy was evaluated by comparing the results of the CE analyses of the dietary supplements with those of the reference United States Pharmacopeial HPLC method. The unpaired t-test did not show a statistically significant difference between the results of both the proposed CE and the reference method (p > 0.05, n = 3).

Development of an adverse outcome pathway network for breast cancer: a comprehensive representation of the pathogenesis, complexity and diversity of the disease.

Adverse outcome pathways (AOPs), introduced in modern toxicology, intend to provide an evidence-based representation of toxicological effects and facilitate safety assessment of chemicals not solely based on laboratory animal in vivo experiments. However, some toxicological processes are too complicated to represent in one AOP. Therefore, AOP networks are developed that help understanding and predicting toxicological processes where complex exposure scenarios interact and lead to the emergence of the adverse outcome. In this study, we present an AOP network for breast cancer, developed after an in-depth survey of relevant scientific literature. Several molecular initiating events (MIE) were identified and various key events that link the MIEs with breast cancer were described. The AOP was developed according to Organization of Economic Co-Operation and Development (OECD) guidance, weight of evidence was assessed through the Bradford Hill criteria and confidence was tested by the OECD key questions. The AOP network provides a straightforward understanding of the disease onset and progression at different biological levels. It can be used to pinpoint knowledge gaps, identify novel therapeutic targets and act as a stepping stone for the development of novel in vitro test methods for hazard identification and risk assessment of newly developed chemicals and drugs.

Cytotoxic, Antioxidant, and Antidiabetic Activities versus UPLC-ESI-QTOF-MS Chemical-Profile Analysis of Ipomoea aquatica Fractions.

Ipomoea aquatica is a common green leafy vegetable that has numerous uses in traditional medicine. This study focused on the determination of the cytotoxic, antiradical, and antidiabetic properties of various fractions of the I. aquatica methanolic extract, as well as on the tentative identification of some bioactive compounds in the same fractions. The cytotoxicity was determined by the brine shrimp lethal test. The antioxidant activities of the I. aquatica fractions were investigated through 3 assays. The antidiabetic activity (in vitro) was measured by α-glucosidase and α-amylase inhibition assays. Phytochemical qualitative analyses demonstrated the presence of alkaloids, terpenoids, phenols, and flavonoids in the ethyl acetate-methanol and methanol fractions. The total phenolic and total flavonoid contents were found to be highest in the ethyl acetate-MeOH fractions. The evaluation of the cytotoxicity showed that the hexane-dichloromethane fraction is the most toxic, while the others are moderately toxic. The antioxidant activity assays showed that the ethyl acetate-MeOH fractions are the most potent, while the α-glucosidase and α-amylase assays revealed that the hexane-dichloromethane fraction might contain a potent antidiabetic agent. Some bioactive substances in the MeOH fractions, such as salicylic acid glucoside, 1-O-sinapoyl-ß-D-glucose derivative, and dihydroferulic acid derivative, were tentatively identified. To the best of our knowledge, this is the first report to detect and identify these compounds in this species. Based on the results of this study, it may be concluded that I. aquatica is a potent antioxidant agent and could be a good candidate as a natural antioxidant in food and therapeutics.

Gas Chromatographic Fingerprint Analysis for the Comparison of Seized Cannabis Samples.

Cannabis sativa L. is widely used as recreational illegal drugs. Illicit Cannabis profiling, comparing seized samples, is challenging due to natural Cannabis heterogeneity. The aim of this study was to use GC-FID and GC-MS herbal fingerprints for intra (within)- and inter (between)-location variability evaluation. This study focused on finding an acceptable threshold to link seized samples. Through Pearson correlation-coefficient calculations between intra-location samples, 'linked' thresholds were derived using 95% and 99% confidence limits. False negative (FN) and false positive (FP) error rate calculations, aiming at obtaining the lowest possible FP value, were performed for different data pre-treatments. Fingerprint-alignment parameters were optimized using Automated Correlation-Optimized Warping (ACOW) or Design of Experiments (DoE), which presented similar results. Hence, ACOW data, as reference, showed 54% and 65% FP values (95 and 99% confidence, respectively). An additional fourth root normalization pre-treatment provided the best results for both the GC-FID and GC-MS datasets. For GC-FID, which showed the best improved FP error rate, 54 and 65% FP for the reference data decreased to 24 and 32%, respectively, after fourth root transformation. Cross-validation showed FP values similar as the entire calibration set, indicating the representativeness of the thresholds. A noteworthy improvement in discrimination between seized Cannabis samples could be concluded.

Defining a standardized methodology for the determination of the antioxidant capacity: case study of Pistacia atlantica leaves.

Antioxidant activity can be measured by a variety of methods, that include hydrogen atom transfer (HAT) and single electron transfer (ET) methods. Most of these techniques are spectrophotometric, and thus incapable of quantifying or indicting individual antioxidant compounds. Nowadays, the integration of chromatographic and chemometric approaches allows a high-throughput identification and activity prediction of herbal products. The ethyl acetate fraction from the aqueous-acetone extract of Pistacia atlantica leaves is frequently used for the isolation of antioxidants. In this study it is investigated for its antioxidant properties in order to define a potential methodology for the determination of the antioxidant capacity of herbal extracts (which need to be confirmed by future studies). The seven free radical assays evaluated can be divided into two groups depending on the oxidizing reagent. Three methods use stable, non-biological radicals, i.e. the diphenyl-1-picrylhydrazyl (DPPH) assay, the azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay, and the N,N-dimethyl-p-phenylenediamine (DMPD) assay, which have no direct physiological importance. Four methods work with biological radical producers, including superoxide anion (O2˙-), hydroxyl (˙OH), nitric oxide (NO˙) and peroxyl (ROO˙) are produced metabolically in living organisms, and thus direct information on an extract's protective action is obtained. Furthermore, the reducing power method by potassium ferricyanide (RPC), and the iron (ferrous) ion chelating activity also have been investigated. The antioxidant activities of the samples were measured according to the different methods and modelled as a function of the HPLC fingerprints using the partial least squares (PLS) technique. The regression coefficients of the models were studied to indicate the peaks potentially responsible for the antioxidant activity. From the combined results of the different PLS models, we recommend using the DPPH, RPC and ROO˙ assays, to evaluate the overall antioxidant capacity; in the case study of P. atlantica leaves.

Defining a system suitability limit to decide on column deterioration and to facilitate column transfers in chiral supercritical fluid chromatography.

The separation of enantiomers is an important requirement during the entire drug life cycle in the pharmaceutical industry. High-performance liquid chromatography and supercritical fluid chromatography (SFC) are the main chromatographic techniques used to separate enantiomers. Since chiral stationary phases are often extensively used once a method has been developed, columns will age and must be replaced after a certain period. However, no practical guidelines exist to determine when a column is deteriorated or to decide whether a transfer to another column (with the same chiral selector) is successful. In this study, a system suitability limit for resolution was defined, based on an intermediate (time-different) precision study in SFC on four immobilized polysaccharide-based columns that only differed in manufacturer or particle size. This system suitability limit could be used to decide on column deterioration or as a requirement to evaluate whether a separation transfer was successful. Some method adaptations may be necessary to obtain successful transfers. An approach was proposed, which helped the analyst to make successful transfers. Graphical abstract.

Stationary-phase optimized selectivity in supercritical fluid chromatography using a customized Phase OPtimized Liquid Chromatography kit: comparison of different prediction approaches.

The use of stationary-phase optimized selectivity in liquid chromatography (SOS-LC) was shown to be successful for HPLC to analyze complex mixtures using a Phase OPtimized Liquid Chromatography (POPLC) kit. This commercial kit contains five stationary-phase types of varying lengths, which can be coupled to offer an improved separation of compounds. Recently, stationary-phase optimized selectivity supercritical fluid chromatography (SOS-SFC) has been introduced, transferring the methodology to SFC. In this study, the applicability of a customized POPLC expert kit for isocratic SFC runs was explored. Five stationary-phase chemistries were selected as potentially most suitable for achiral separations of polar compounds: aminopropyl (amino), cyanopropyl (CN), diol, ethylpyridine (EP), and silica. The retention factors (k) on the individual stationary phases were used for the prediction of the best stationary-phase combination, based on the POPLC algorithm (via the included software). As an alternative, the best column combination was predicted using multiple linear regression (MLR) models on the results obtained from a simplex centroid mixture design with only three stationary-phase types (amino, silica, and EP). A third approach applied the isocratic POPLC algorithm on the same three stationary-phase data. The proposed combinations were assembled and tested. The predicted and experimental retention factors were compared. The predictions based on the POPLC algorithm provided a stationary phase showing a complete separation of the mixture. The stationary phase suggested by the MLR models, on the other hand, showed co-elution of two compounds, due to an unexpected experimental retention shift. Overall, the customized POPLC kit showed good potential to be applied in SFC. Graphical abstract.

Bioactive Azepine-Indole Alkaloids from Psychotria nemorosa.

Phytochemical investigation of the alkaloid extract of the aerial parts of Psychotria nemorosa led to the isolation and characterization of 10 azepine-indole alkaloids, i.e., cimitrypazepine (1), fargesine (2), nemorosines A (3), and B (12), nemorosinosides A-F (4-9), as well as two ß-carboline derivatives, 10-hydroxyisodolichantoside (10) and 10-hydroxydolichantoside (11), an isoxazole alkaloid, nemorosinoside G (13), serotonin (14), bufotenine (15), and (S)-gentianol (16). Compounds 3-13 have not yet been described. These compounds were isolated by semipreparative HPLC, and their structures were determined by means of HRMS, NMR, and ECD measurements. In addition, the monoamine oxidase-A (MAO-A), MAO-B, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibitory activities were evaluated. Alkaloids 1-3 inhibited the MAO-A activity with IC50 values of 1.4, 1.4, and 0.9 µM, respectively.

Xanthones and Cancer: from Natural Sources to Mechanisms of Action.

Xanthones are a class of heterocyclic natural products that have been widely studied for their pharmacological potential. In fact, they have been serving as scaffolds for the design of derivatives focusing on drug development. One of the main study targets of xanthones is their anticancer activity. Several compounds belonging to this class have already demonstrated cytotoxic and antitumor effects, making it a promising group for further exploration. This review therefore focuses on recently published studies, emphasizing their natural and synthetic sources and describing the main mechanisms of action responsible for the anticancer effect of promising xanthones.

A new potential anti-cancer beta-carboline derivative decreases the expression levels of key proteins involved in glioma aggressiveness: A proteomic investigation.

Gliomas remain highly fatal due to their high resistance to current therapies. Deregulation of protein synthesis contributes to cancer onset and progression and is a source of rising interest for new drugs. CM16, a harmine derivative with predicted high blood-brain barrier penetration, exerts antiproliferative effects partly through translation inhibition. We evaluated herein how CM16 alters the proteome of glioma cells. The analysis of the gel-free LC/MS and auto-MS/MS data showed that CM16 induces time- and concentration-dependent significant changes in the total ion current chromatograms. In addition, we observed spontaneous clustering of the samples according to their treatment condition and their proper classification by unsupervised and supervised analyses, respectively. A two-dimensional gel-based approach analysis allowed us to identify that treatment with CM16 may downregulate four key proteins involved in glioma aggressiveness and associated with poor patient survival (HspB1, BTF3, PGAM1, and cofilin), while it may upregulate galectin-1 and Ebp1. Consistently with the protein synthesis inhibition properties of CM16, HspB1, Ebp1, and BTF3 exert known roles in protein synthesis. In conclusion, the downregulation of HspB1, BTF3, PGAM1 and cofilin bring new insights in CM16 antiproliferative effects, further supporting CM16 as an interesting protein synthesis inhibitor to combat glioma.

Assessing the suitability of capillary electrophoresis-mass spectrometry for biomarker discovery in plasma-based metabolomics.

The actual utility of capillary electrophoresis-mass spectrometry (CE-MS) for biomarker discovery using metabolomics still needs to be assessed. Therefore, a simulated comparative metabolic profiling study for biomarker discovery by CE-MS was performed, using pooled human plasma samples with spiked biomarkers. Two studies have been carried out in this work. Focus of study I was on comparing two sets of plasma samples, in which one set (class I) was spiked with five isotope-labeled compounds, whereas another set (class II) was spiked with six different isotope-labeled compounds. In study II, focus was also on comparing two sets of plasma samples, however, the isotope-labeled compounds were spiked to both class I and class II samples but with concentrations which differ by a factor two between both classes (with one compound absent in each class). The aim was to determine whether CEMS-based metabolomics could reveal the spiked biomarkers as the main classifiers, applying two different data analysis software tools (MetaboAnalyst and Matlab). Unsupervised analysis of the recorded metabolic profiles revealed a clear distinction between class I and class II plasma samples in both studies. This classification was mainly attributed to the spiked isotope-labeled compounds, thereby emphasizing the utility of CE-MS for biomarker discovery.

In vitro antileishmanial and cytotoxicity activities of essential oils from Haplophyllum tuberculatum A. Juss leaves, stems and aerial parts.

BACKGROUND: Plants used for traditional medicine produce diverse and complex secondary metabolites exhibiting various medicinal properties. The medicinal plant Haplophyllum tuberculatum is used by native people against malaria and parasitic infections. METHODS: In this study and in order to contribute for the search of new natural drugs for leishmaniasis, the essential oils of H. tuberculatum leaves, stems and aerial parts (leaves+stems) collected in two different periods, 2013 and 2015, and their components by GC/FID and GC/MS analyses were investigated. Those collected in 2013 were also re-analyzed two years later. The extracted oils were screened in vitro for anti-leishmanial activity on Leishmania mexicana mexicana (L.m.m.) promastigotes and cytotoxicity on the Chinese Hamster Ovary (CHO) cell line. Limonene (1.5 - 8%), its isomers (R- (+)-limonene and S-(-)-limonene), linalool and octanol were also tested. RESULTS: Results showed that the chemical composition varied according to the year of collection. Though major compounds remain almost the same, qualitative and quantitative variations in the composition of the EOs can be observed between the two years of collection, with some minor compounds identified only in one type of samples. Variation in the composition were also observed in the re-analyzed volatile oils, showing stability concerns. The essential oils and R-(+)-limonene showed moderate anti-leishmanial activity. Their IC50 range from 6.48 to 50.28 µg/ml. Cytotoxicity assays for theses volatile extracts, R- (+)-limonene and S- (-)-limonene on CHO cells showed relatively potent cytotoxicity with a selectivity index <10. Their CC50 range from 27.79 to 82.56 µg/ml. CONCLUSIONS: The findings of the present study demonstrated that H. tuberculatum might not be considered as a natural source for production of new anti-leishmanial agents without further analyzing its eventual in vivo toxicity as well as that of major pure compounds.

Identification of some Bioactive Metabolites in a Fractionated Methanol Extract from Ipomoea aquatica (Aerial Parts) through TLC, HPLC, UPLC-ESI-QTOF-MS and LC-SPE-NMR Fingerprints Analyses.

INTRODUCTION: The plant species Ipomoea aquatica contains various bioactive constituents, e.g. phenols and flavonoids, which have several medical uses. All previous studies were executed in Asia; however, no reports are available from Africa, and the secondary metabolites of this plant species from Africa are still unknown. OBJECTIVE: The present study aims finding suitable conditions to identify the bioactive compounds from different fractions. METHODOLOGY: Chromatographic fingerprint profiles of different fractions were developed using high-performance liquid chromatography (HPLC) and then these conditions were transferred to thin-layer chromatography (TLC). Subsequently, the chemical structure of some bioactive compounds was elucidated using ultra-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UPLC-QTOF-MS) and liquid chromatography-solid phase extraction-nuclear magnetic resonance (LC-SPE-NMR) spectroscopy. RESULTS: The HPLC fingerprints, developed on two coupled Chromolith RP-18e columns, using a gradient mobile phase (methanol/water/trifluoroacetic acid, 5:95:0.05, v/v/v), showed more peaks than the TLC profile. The TLC fingerprint allows the identification of the types of chemical constituents, e.g. flavonoids. Two flavonoids (nicotiflorin and ramnazin-3-O-rutinoside) and two phenolic compounds (dihydroxybenzoic acid pentoside and di-pentoside) were tentatively identified by QTOF-MS, while NMR confirmed the structure of rutin and nicotiflorin. CONCLUSION: The HPLC and TLC results showed that HPLC fingerprints give more and better separated peaks, but TLC helped in determining the class of the active compounds in some fractions. Bioactive constituents were identified as well using MS and NMR analyses. Two flavonoids and two phenolic compounds were tentatively identified in this species for the first time, to the best of our knowledge. Copyright © 2017 John Wiley & Sons, Ltd.

Fatty Acids-Based Quality Index to Differentiate Worldwide Commercial Pistachio Cultivars.

The fatty acid profiles of five main commercial pistachio cultivars, including Ahmad-Aghaei, Akbari, Chrok, Kalle-Ghouchi, and Ohadi, were determined by gas chromatography: palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3), arachidic (C20:0), and gondoic (C20:1) acid. Based on the oleic to linoleic acid (O/L) ratio, a quality index was determined for these five cultivars: Ohadi (2.40) < Ahmad-Aghaei (2.60) < Kale-Ghouchi (2.94) < Chrok (3.05) < Akbari (3.66). Principal component analysis (PCA) of the fatty acid data yielded three significant PCs, which together account for 80.0% of the total variance in the dataset. A linear discriminant analysis (LDA) model that was evaluated with cross-validation correctly classified almost all of the samples: the average percent accuracy for the prediction set was 98.0%. The high predictive power for the prediction set shows the ability to indicate the cultivar of an unknown sample based on its fatty acid chromatographic fingerprint.

Interinstrumental transfer of a fast short-end injection capillary electrophoresis method: Application to the separation of niobium, tantalum, and their substituted ions.

The interinstrumental transfer of a short-end CE method was studied. A model separation of the hexameric forms of niobium, tantalum, and their substituted ions (Nb6-x Tax with 0 ≤ x ≤ 6) was selected as test case. The method was first optimized on a Beckman instrument and in a second step transferred to an Agilent instrument. The transfer needed updated guidelines that tackled differences in effective capillary length, 8.5 (Agilent) versus 10 cm (Beckman), because of instrumental different capillary cartridges. Differences in effective length lead to migration time and separation efficiency inequalities, illustrated by a decrease in resolution between the substituted ions. The difference in effective length was overcome by adapting the lift offset parameter of the Agilent instrument. The lift offset default setting is 4 mm and by increasing this parameter both the inlet and outlet lifts are lowered and thus the detection window can be displaced and consequently the effective length was increased. The decrease in effective length difference and the effect on the separation efficiency was investigated and led finally to a restored separation of the substituted ions. The adaptation of the lift offset parameter during short-end injection methods was added to earlier developed guidelines to facilitate interinstrumental method transfer of CE methods.

Seasonal, gender and regional variations in total phenolic, flavonoid, and condensed tannins contents and in antioxidant properties from Pistacia atlantica ssp. leaves.

CONTEXT: The widespread use of Pistacia atlantica Desf. ssp. (Anacardiaceae) in traditional medicine can be partly attributed to the content of its secondary metabolites, in particular, the phenolic compounds. OBJECTIVE: The effects of harvest period, growing region and gender on the phenolic compounds, flavonoids and condensed tannins contents were studied, as well as on the antioxidant activities of P. atlantica leaves in order to provide a scientific basis for optimal collection. MATERIALS AND METHODS: Leaves were collected monthly from April to October 2010 in two Algerian sites. The powdered leaves were used for preparing the ethyl acetate extract. Contents of total phenolics (TPC), flavonoids (FC) and condensed tannins (CTC) were determined spectrophotometrically. Antioxidant activity was evaluated through radical scavenging activity (RSA) of 2,2-diphenyl-1-picrylhydrazyl (250 µM) and the reducing power capacity (RPC) determination by K3Fe(CN)6 (1%). RESULTS: The TPC was found to vary from 79 ± 13 to 259 ± 8 mg gallic acid equivalents/g of dry weight (DW) during the study period. The RSA and RPC varied between 262 ± 18 and 675 ± 21 mg Ascorbic Acid Equivalent (AAE)/g DW, and from 259 ± 16 to 983 ± 20 mg AAE/g DW, respectively. A seasonal pattern was observed consisting of a decrease in TPC content and RPC from spring to autumn. The FC, CTC and RSA did not show a seasonal pattern. DISCUSSION AND CONCLUSION: Our findings showed that secondary metabolite content and antioxidant activities of P. atlantica leaves were more influenced by harvest time and growing region than by gender.

Interinstrumental method transfer of a capillary electrophoretic separation of angiotensin II and five derivatives: Evaluation and update of earlier developed guidelines.

The increased interest in the separation of peptides, proteins, immunoglobulins, and polynucleotides, led to an increased demand for appropriate analytical methodologies and instrumentation. CE, because of its unique separation mechanism and high efficiency, is frequently used in the analysis of those molecules. In this study, a CE method for the separation of six angiotensin analogues was developed in the first step. In the second step, the method was transferred to a CE instrument of another brand, taking into account guidelines defined earlier about the interinstrumental transfer of CE methods. Although previously successful, the application of these guidelines during this study was not able to maintain the baseline separation. Further research on the instrumental differences revealed that the electrical resistance on both instruments differed. At constant current, the electrical resistance, generated voltage, and separation efficiency on the Agilent instrument were lower than on the Beckman instrument. Increase of the electrical resistance, by reducing the capillary temperature, leads to an increased applied voltage and separation efficiency on the Agilent system. The guidelines developed earlier were, therefore, updated with an additional step equalizing the electrical resistances, which led to a successful interinstrumental analytical method transfer for the separation of six angiotensin derivatives.