Four Pistacia atlantica subspecies (atlantica, cabulica, kurdica and mutica): A review of their botany, ethnobotany, phytochemistry and pharmacology.

ETHNOPHARMACOLOGICAL RELEVANCE: Pistacia atlantica (wild pistachio) belongs to the Anacardiaceae family, and growing from the Mediterranean basin to central Asia, especially in Iran, Turkey, Iraq and Saudi Arabia where it is extensively used in traditional medicine for a wide range of ailments related to relieving upper abdominal discomfort and pain, dyspepsia and peptic ulcer. OBJECTIVE: Despite the diverse biological activities of P. atlantica, there is no current review summarizing medicinal properties of its subspecies, including cabulica, kurdica and mutica. Thus, this paper aims to explore the current understanding of the chemical, pharmacological, and biochemical properties of the extracts and the main active constituents found in each subspecies of this plant. METHODS: Peer-reviewed articles, using "Pistacia atlantica" as search term (″all fields″), were retrieved from Scifinder, Pubmed, Science direct, Wiley, Springer, ACS, Scielo, Web of Science and other web search instruments (Google Scholar, Yahoo search). Papers published until July 2020 are considered. In addition, various books were consulted that contained botanical and ethnopharmacological information. The information provided in this review is based on peer-reviewed papers in English and French. RESULTS: Phytochemical studies have shown the presence of numerous valuable compounds, including volatile compounds, flavonoids, phenolic compounds, fatty acids, tocopherols and phytosterols. P. atlantica contains also minerals and trace elements, like iron, lead, copper, potassium, sodium and calcium; fatty acids, like oleic, linoleic, and palmitic acid; fat-soluble vitamins, such as α, ß, γ and δ tocopherols; phytosterols, like betasitosterol, stigmasterol, campesterol and Δ5-avenasterol. Crude extracts and isolated compounds from P. atlantica show a wide range of pharmacological properties, such as antimicrobial, antifungal, anti-inflammatory, analgesic, antinociceptive, wound healing, anticancer, cytotoxic, anticholinesterase, antidiabetic, hepatoprotective, urease inhibition, antihypertension, nipple fissure healing, antileishmanial and antiplasmodial activities. However, there are no reports summarizing the P. atlantica bioactivity, its therapeutic value, and the roles played by each of the numerous phytoconstituents. CONCLUSION: Many traditional uses of P. atlantica and its subspecies have now been confirmed by pharmacologic research. Systematic phytochemical investigation of the P. atlantica subspecies and the pharmacological properties, especially the mechanisms of action and toxicology, to illustrate their ethnomedicinal use, to explore the therapeutic potential and support further health-care product development, will undoubtedly be the focus of further research. Therefore, detailed and extensive studies and clinical evaluation of P. atlantica subspecies should be carried out in future for the safety approval of therapeutic applications.

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.

Potentially antidiabetic and antihypertensive compounds identified from Pistacia atlantica leaf extracts by LC fingerprinting.

The objective of this paper is to evaluate the variations in the ability of Pistacia atlantica leaves to inhibit enzymes linked to type 2 diabetes (α-amylase and α-glucosidase) and to hypertension (angiotensin converting enzyme-I (ACE-I)), depending on harvesting month, gender and growing region, as well as to identify the peaks in chromatographic fingerprints that potentially correspond to components with enzymatic inhibitory activities. In this study, LC fingerprints of P. atlantica leave extracts were developed. Peaks which were probably responsible for the anti-amylase, anti-glucosidase and anti-ACE-I activities were assigned. For the latter purpose, the relevant information was extracted, linking the chromatographic fingerprints with the activities using a linear multivariate calibration technique, i.e., Partial Least Squares (PLS) regression. Prior to the construction of the models, the fingerprints are aligned using a warping method, called Correlation Optimized Warping (COW). Besides COW, different other data pretreatment methods were applied and compared. Our findings revealed that the influence of the growing region and gender on the α-amylase, α-glucosidase and ACE-I inhibitory activities of P. atlantica leaves was less important than the harvest time. Thirteen common peaks were selected from the chromatograms and used as a dataset to model the biological activities. The peaks potentially responsible for the biological activity of the samples were indicated by studying the regression coefficients of the models. Seven peaks corresponding to possibly anti-amylase compounds were found, while 6 peaks were considered important for inhibiting the α-glucosidase activity. Furthermore, the regression coefficients of the hypertension model indicated eight peaks as being important for inhibiting the ACE-I activity. The contributions of individual phenolic compounds of P. atlantica leaves to the α-amylase, α-glucosidase and ACE-I inhibitory activities were also identified. This investigation showed that the extract of P. atlantica leaves provides a rational basis for the isolation and development of antidiabetic and antihypertensive agents.

Computed determination of the in vitro optimal chemocombinations of sphaeropsidin A with chemotherapeutic agents to combat melanomas.

PURPOSE: Evasion to new treatments of advanced melanoma is still associated with a poor prognosis. Choosing the best combination of agents that can bypass resistance mechanisms remains a challenge. Sphaeropsidin A (Sph A) is a fungal bioactive secondary metabolite previously shown to force melanoma cells to undergo apoptosis via cell volume dysregulation. This work studied its in vitro combination with cytotoxic chemotherapeutics in a rational manner. METHODS: Four melanoma cell lines harboring different sensitivity levels to pro-apoptotic stimuli were used to build a predictive response surface model allowing the determination of the optimal in vitro combinations of Sph A with two drugs, i.e., cisplatin or temozolomide, owing to a limited set of experimentations. RESULTS: Testing 12 experimental combinations allowed us to build an accurate predictive model that considers the complexity of the drug interaction and determines the optimal combinations according to the endpoint chosen, i.e., the maximal cytotoxic effects. Therefore, combining 4 µM Sph A with 75 µM cisplatin concomitantly for 72 h improved its cytotoxic effects on melanoma cells in a synergistic manner. An optimal in vitro treatment schedule was also obtained for temozolomide. CONCLUSIONS: The use of a response surface model offers the possibility of reducing the experiments while determining accurately the optimal combinations. We herein highlighted that combining the Na+/K+/2Cl- cotransporter and/or anion exchanger inhibitor Sph A with chemotherapeutic agents could improve the therapeutic benefits of conventional chemotherapies against advanced melanomas, particularly because Sph A exerts cytotoxic effects regardless of the genetic BRAF and NRAS status.

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.

LC-MS analysis combined with principal component analysis and soft independent modelling by class analogy for a better detection of changes in N-glycosylation profiles of therapeutic glycoproteins.

Therapeutic proteins are among the top selling drugs in the pharmaceutical industry. More than 60 % of the approved therapeutic proteins are glycosylated. Nowadays, it is well accepted that changes in glycosylation may affect the safety and the efficacy of the therapeutic proteins. For this reason, it is important to characterize both the protein and the glycan structures. In this study, analytical and data processing methods were developed ensuring an easier characterization of glycoprofiles. N-glycans were (i) enzymatically released using peptide-N-glycosidase F (PNGase F), (ii) reduced, and (iii) analyzed by hydrophilic interaction liquid chromatography coupled to a high-resolution mass spectrometer (HILIC-HRMS). Glycosylation changes were analyzed in human plasma immunoglobulin G samples which had previously been artificially modified by adding other glycoproteins (such as ribonuclease B and fetuin) or by digesting with enzyme (neuraminidase). Principal component analysis (PCA) and classification through soft independent modelling by class analogy (SIMCA) were used to detect minor glycosylation changes. Using HILIC-MS-PCA/SIMCA approach, it was possible to detect small changes in N-glycosylation, which had not been detected directly from the extracted-ion chromatograms, which is current technique to detect N-glycosylation changes in batch-to-batch analysis. The HILIC-MS-PCA/SIMCA approach is highly sensitive approach due to the sensitivity of MS and appropriate data processing approaches. It could help in assessing the changes in glycosylation, controlling batch-to-batch consistency, and establishing acceptance limits according to the glycosylation changes, ensuring safety and efficacy. Graphical abstract N-glycosylation characterization using LC-MS-PCA approach.

Batch-to-batch N-glycosylation study of infliximab, trastuzumab and bevacizumab, and stability study of bevacizumab.

OBJECTIVES: Infliximab, trastuzumab and bevacizumab are among the most frequently prescribed therapeutic proteins, and like most other therapeutic proteins, are glycosylated. As differences in glycosylation may significantly change the safety and efficacy of therapeutic glycoproteins, it is extremely important to control N-glycosylation consistency. In the first part of this study, the batch-to-batch consistency of the N-glycosylation of infliximab, trastuzumab and bevacizumab was analysed. In the second part, the consistency of the N-glycosylation of bevacizumab stored in polycarbonate syringes (for off-label drug use) for 3 months was examined. METHODS: N-glycans were (i) enzymatically released using peptide-N-glycosidase F, (ii) reduced, and (iii) analysed using hydrophilic interaction liquid chromatography coupled with high-resolution mass spectrometry. Mass spectrometry data were interpreted using principal component analysis combined with two-way analysis of variance and Tukey post hoc tests. The biological activity of infliximab and trastuzumab was examined using enzyme-linked immunosorbent assays. RESULTS: The results of both studies make important contributions to the field of hospital pharmacy. All batches of the studied therapeutic glycoproteins (infliximab, trastuzumab and bevacizumab) varied considerably (especially in galactosylation), while the N-glycosylation of bevacizumab remained unchanged during 3-month storage. CONCLUSIONS: Threshold values for batch-to-batch N-glycosylation variations should be established and batch-to-batch glycosylation consistency should be regularly tested. In our study, samples with significantly different N-glycosylation profiles showed no significant variations in biological activity, suggesting that the differences are probably not therapeutically significant.

Glycan characterization of biopharmaceuticals: Updates and perspectives.

Therapeutic proteins are rapidly becoming the most promising class of pharmaceuticals on the market due to their successful treatment of a vast array of serious diseases, such as cancers and immune disorders. Therapeutic proteins are produced using recombinant DNA technology. More than 60% of therapeutic proteins are posttranslationally modified following biosynthesis by the addition of N- or O-linked glycans. Glycosylation is the most common posttranslational modifications of proteins. However, it is also the most demanding and complex posttranslational modification from the analytical point of view. Moreover, research has shown that glycosylation significantly impacts stability, half-life, mechanism of action and safety of a therapeutic protein. Considering the exponential growth of biotherapeutics, this present review of the literature (2009-2015) focuses on the characterization of protein glycosylation, which has witnessed an improvement in methodology. Furthermore, it discusses current issues in the fields of production and characterization of therapeutic proteins. This review also highlights the problem of non-standard requirements for the approval of biosimilars with regard to their glycosylation and discusses recent developments and perspectives for improved glycan characterization.

Comparison of a triple-quadrupole and a quadrupole time-of-flight mass analyzer to quantify 16 opioids in human plasma.

The aim of this work is to study whether a quadrupole time-of-flight (QToF) mass analyzer, coupled to an ultra high performance liquid chromatography (UHPLC) system, can be a valuable alternative for a triple-quadrupole (QqQ) mass analyzer, for quantitative toxicological purposes. The case study considered was the quantification of 16 opioids (6-monoacetylmorphine, buprenorphine, codeine, dihydrocodeine, ethylmorphine, fentanyl, hydrocodone, hydromorphone, morphine, norbuprenorphine, norcodeine, norfentanyl, oxycodone, oxymorphone, pholcodine and tilidine) in human plasma. Both methods were validated in parallel in terms of selectivity, matrix effects, extraction recovery, carry-over, bias, precision and sensitivity. Accuracy-profile methodology was used to determine the optimal calibration model, and to estimate bias, repeatability, intermediate precision and total error. Selectivity was demonstrated for all opioids and deuterated analogues, except for codeine-d3 on the UHPLC-QTOF. For most compounds, extraction recoveries were in the range 60 to 80% on both systems, except for the synthetic analogues, buprenorphine, fentanyl and tilidine, where large variability is observed. Carry-over was negligible on both systems. For different opioids, the optimal calibration model was different between the systems. The accuracy profiles of the majority of the opioids indicated that, over the entire tested concentration range, for more than 5% of the future measurements, total errors are expected to exceed the a priori defined 15% acceptance limit. For some exceptions, however, the measurements even suffer from total errors above 30%, which can be attributed to the solid phase extraction procedure that was applied as sample pretreatment technique. Sensitivity was generally tenfold better on the LC-QToF system, probably due to the difference in ion choice for quantification between both systems. In conclusion, the best performing system seemed to depend on the compound, on the parameter and even on the concentration. Accuracy profiles clearly provided valuable information complementary to that obtained in classical validation tests, and therefore preferably are taken into account when deciding on a method's performance.

An improved microbore UHPLC method with electrochemical detection for the simultaneous determination of low monoamine levels in in vivo brain microdialysis samples.

The simultaneous determination of the monoamines dopamine (DA), noradrenaline (NA) and serotonin (5-HT) in in vivo microdialysis samples remains challenging because of the low extracellular neurotransmitter levels in different brain regions, specific sample characteristics, and the quest for high temporal resolution and a multi-target strategy in neuropharmacological research. A fast and sensitive microbore (1.0mm i.d. column) UHPLC method coupled to electrochemical detection (ECD) is developed by means of design of experiments with the emphasis on sufficient retention of NA within an acceptable total analysis time. Indeed, NA is the earliest eluting compound and often interferes with the broad solvent front originating from the sample matrix. The sensitive UHPLC-ECD assay (LLOQ of 100pM for NA and 150pM for DA and 5-HT) with an analysis time of 8min for standard solutions and 20min for in vivo microdialysis samples originating from rat hippocampus, prefrontal cortex and striatum, is validated applying accuracy profiles. The combination of in vivo microdialysis and microbore UHPLC-ECD has shown to be particularly suitable for future contributions to neuropharmacological research on the monoaminergic system.

An experimental design approach to optimize an amperometric immunoassay on a screen printed electrode for Clostridium tetani antibody determination.

An immunoassay for the determination of anti-tetani antibodies has been developed using a screen printed electrode (SPE) as solid support for toxoid (antigen) immobilization. The assay was performed in guinea pig serum. The immunoreaction and the subsequent amperometric detection occurred directly onto the SPE surface. The assay consisted of spiking the anti-tetani sample directly onto the toxoid modified SPE, and then a second antibody, i.e. a HRP-labeled anti-immunoglobulin G, was deposited onto the biosensor. Subsequent amperometric detection was realized by spiking 10 µL of a hydroquinone (HQ) solution into 40 µL of buffer solution containing hydrogen peroxide. An experimental design approach was implemented for the optimization of the immunoassay. The variables of interest, such as bovine serum albumin (BSA) concentration, incubation times and labeled antibody dilution, were optimized with the aid of the response surface methodology using a circumscribed central composite design (CCCD). It was observed that two factors exhibited the greatest impact on the response, i.e. the anti-tetani incubation time and the dilution factor of the labeled antibody. It was discovered that in order to maximize the response, the dilution factor should be small, while the anti-tetani antibody incubation time should be long. The BSA concentration and the HRP-anti-IgG incubation had very limited influence. Under the optimized conditions, the immunoassay had a limit of detection of 0.011 IU/mL and a limit of quantification of 0.012 IU/mL. These values were below the protective human antibody limit of 0.06 IU/mL.

Inter-instrumental method transfer of chiral capillary electrophoretic methods using robustness test information.

Capillary electrophoresis (CE) is an electrodriven separation technique that is often used for the separation of chiral molecules. Advantages of CE are its flexibility, low cost and efficiency. On the other hand, the precision and transfer of CE methods are well-known problems of the technique. Reasons for the more complicated method transfer are the more diverse instrumental differences, such as total capillary lengths and capillary cooling systems; and the higher response variability of CE methods compared to other techniques, such as liquid chromatography (HPLC). Therefore, a larger systematic change in peak resolutions, migration times and peak areas, with a loss of separation and efficiency may be seen when a CE method is transferred to another laboratory or another type of instrument. A swift and successful method transfer is required because development and routine use of analytical methods are usually not performed in the same laboratory and/or on the same type of equipment. The aim of our study was to develop transfer rules to facilitate CE method transfers between different laboratories and instruments. In our case study, three ß-blockers were chirally separated and inter-instrumental transfers were performed. The first step of our study was to optimise the precision of the chiral CE method. Next, a robustness test was performed to identify the instrumental and experimental parameters that were most influencing the considered responses. The precision- and the robustness study results were used to adapt instrumental and/or method settings to improve the transfer between different instruments. Finally, the comparison of adapted and non-adapted transfers allowed deriving some rules to facilitate CE method transfers.

Precision evaluation of chiral capillary electrophoretic methods in the context of inter-instrumental transfer: constant current versus constant voltage application.

Capillary electrophoresis (CE) is an electrophoretic separation technique that was rapidly increasing in popularity some years ago and that led to high expectations. Because of their different separation mechanisms, CE and HPLC are alternative and complementary separation techniques. Chiral molecules can be directly separated with CE by simply adding a chiral selector to the running buffer solution, leading to flexible and cheap methods. Major drawbacks of capillary electrophoretic separation methods are, however, the lower precision compared to HLPC methods and a more problematic analytical method transfer. Both above stated disadvantages limit the generalized use of CE methods in the pharmaceutical industry. Multiple solutions have been suggested to improve the precision of CE methods. In this work the application of a constant current during the electrophoretic separation instead of the more commonly used application of a constant voltage was studied on two CE instruments with different cooling mechanisms. This was done in the context of optimizing method transfer conditions. A constant current may reduce the generation of heat in the capillary and the consequentially radial and axial temperature fluctuations that both negatively influence the precision of the peak areas, migration times and resolutions of a CE method. The repeatability and time-different intermediate precision of both electrophoretic separation modes were compared on two different CE instruments after a successful analytical method transfer. The chiral separations of three beta-blockers, propranolol, sotalol and betaxolol, were used as test cases. A constant current led to a general improvement of the repeatability and time-different intermediate precision of the relative Area Under the Curve of all three beta-blockers, while that of the migration times remained rather constant. It also led to more similar electropherograms than the application of a constant voltage.

Exploration and classification of chromatographic fingerprints as additional tool for identification and quality control of several Artemisia species.

The World Health Organization accepts chromatographic fingerprints as a tool for identification and quality control of herbal medicines. This is the first study in which the distinction, identification and quality control of four different Artemisia species, i.e. Artemisia vulgaris, A. absinthium, A. annua and A. capillaris samples, is performed based on the evaluation of entire chromatographic fingerprint profiles developed with identical experimental conditions. High-Performance Liquid Chromatography (HPLC) with Diode Array Detection (DAD) was used to develop the fingerprints. Application of factorial designs leads to methanol/water (80:20 (v/v)) as the best extraction solvent for the pulverised plant material and to a shaking bath for 30 min as extraction method. Further, so-called screening, optimisation and fine-tuning phases were performed during fingerprint development. Most information about the different Artemisia species, i.e. the highest number of separated peaks in the fingerprint, was acquired on four coupled Chromolith columns (100 mm × 4.6 mm I.D.). Trifluoroacetic acid 0.05% (v/v) was used as mobile-phase additive in a stepwise linear methanol/water gradient, i.e. 5, 34, 41, 72 and 95% (v/v) methanol at 0, 9, 30, 44 and 51 min, where the last mobile phase composition was kept isocratic till 60 min. One detection wavelength was selected to perform data analysis. The lowest similarity between the fingerprints of the four species was present at 214 nm. The HPLC/DAD method was applied on 199 herbal samples of the four Artemisia species, resulting in 357 fingerprints. The within- and between-day variation of the entire method, as well as the quality control fingerprints obtained during routine analysis, were found acceptable. The distinction of these Artemisia species was evaluated based on the entire chromatographic profiles, developed by a shared method, and visualised in score plots by means of the Principal Component Analysis (PCA) exploratory data-analysis technique. Samples of different quality could be indicated on the score plots. No multi-component analysis was required to reach the goal. Furthermore, differences related to the origin of some of the not-certified samples were shown. The importance of the specific herbal part used for its identification was also presented. In addition, no differences were observed among fingerprints of lyophilised or conditioned-air dried samples. Finally, a classification technique, Soft Independent Modelling by Class Analogy (SIMCA), was successfully evaluated as identification technique for unknown samples. Six additional Artemisia species (29 herbal samples) were identified as not belonging to any of the four modelled classes. The developed chromatographic fingerprints and the evaluation of the entire profiles provide an added value to the distinction, identification and quality control of the simultaneously investigated Artemisia species.

Experimental design methodologies in the optimization of chiral CE or CEC separations: an overview.

In this chapter, an overview of experimental designs to develop chiral capillary electrophoresis (CE) and capillary electrochromatographic (CEC) methods is presented. Method development is generally divided into technique selection, method optimization, and method validation. In the method optimization part, often two phases can be distinguished, i.e., a screening and an optimization phase. In method validation, the method is evaluated on its fit for purpose. A validation item, also applying experimental designs, is robustness testing. In the screening phase and in robustness testing, screening designs are applied. During the optimization phase, response surface designs are used. The different design types and their application steps are discussed in this chapter and illustrated by examples of chiral CE and CEC methods.

Feature selection methods in QSAR studies.

A quantitative structure-activity relationship (QSAR) relates quantitative chemical structure attributes (molecular descriptors) to a biological activity. QSAR studies have now become attractive in drug discovery and development because their application can save substantial time and human resources. Several parameters are important in the prediction ability of a QSAR model. On the one hand, different statistical methods may be applied to check the linear or nonlinear behavior of a data set. On the other hand, feature selection techniques are applied to decrease the model complexity, to decrease the overfitting/overtraining risk, and to select the most important descriptors from the often more than 1000 calculated. The selected descriptors are then linked to a biological activity of the corresponding compound by means of a mathematical model. Different modeling techniques can be applied, some of which explicitly require a feature selection. A QSAR model can be useful in the design of new compounds with improved potency in the class under study. Only molecules with a predicted interesting activity will be synthesized. In the feature selection problem, a learning algorithm is faced with the problem of selecting a relevant subset of features upon which to focus attention, while ignoring the rest. Up to now, many feature selection techniques, such as genetic algorithms, forward selection, backward elimination, stepwise regression, and simulated annealing have been used extensively. Swarm intelligence optimizations, such as ant colony optimization and partial swarm optimization, which are feature selection techniques usually simulated based on animal and insect life behavior to find the shortest path between a food source and their nests, recently are also involved in QSAR studies. This review paper provides an overview of different feature selection techniques applied in QSAR modeling.

Identification by LC-ESI-MS of flavonoids responsible for the antioxidant properties of Mallotus species from Vietnam.

Several Mallotus species (Euphorbiaceae) are used in Vietnam as edible plants or as traditional medicines for different indications, some related to the treatment of inflammatory diseases. This study investigated the antioxidant activities of 33 samples from 17 Vietnamese Mallotus species. We also evaluated potential cytotoxic activity against human cervix carcinoma HeLa and human lung fibroblast WI-38 cells. Our aim is to develop safe dietary supplements with a protective effect against various diseases caused by tissue damage and the acceleration of the aging process linked to reactive oxygen species. These tests allowed the identification of non-cytotoxic plant species exhibiting significant antiradical properties. These antioxidant properties may be explained by their polyphenol composition. The antioxidant activity of the most active Mallotus species was further analyzed with and without tannins removal. We also identified by LC-ESI-MS some flavonoids responsible for a part of this activity.

Experimental designs and their recent advances in set-up, data interpretation, and analytical applications.

In this review, the set-up and data interpretation of experimental designs (screening, response surface, and mixture designs) are discussed. Advanced set-ups considered are the application of D-optimal and supersaturated designs as screening designs. Advanced data interpretation approaches discussed are an adaptation of the algorithm of Dong and the estimation of factor effects from supersaturated design results. Finally, some analytical applications in separation science, on the one hand, and formulation-, product-, or process optimization, on the other, are discussed.

Chromatographic separation techniques and data handling methods for herbal fingerprints: a review.

As herbal medicines have an important position in health care systems worldwide, their current assessment and quality control are a major bottleneck. Over the past decade, major steps were taken not only to improve the quality of the herbal products but also to develop analytical methods ensuring their quality. Nowadays, chromatographic fingerprinting is the generally accepted technique for the assessment and quality control of herbal products. This paper briefly considers the evolution of the regulations and guidelines on the quality control of herbal medicines, and reviews the established analytical techniques for herbal fingerprinting with an emphasis on the most recent developments, such as miniaturized techniques, new stationary phases, analysis at high temperatures and multi-dimensional chromatography. Accessory to the new analytical techniques, the chemometric data handling techniques applied are discussed. Chemometrics provide scientists with useful tools in understanding the huge amounts of data generated by the analytical advances and prove to be valuable for quality control, classification and modelling of, and discrimination between herbal fingerprints.

Rational use of stacking principles for signal enhancement in capillary electrophoretic separations of poliovirus samples.

The use of an earlier developed capillary electrophoresis (CE) method, either to investigate poliovirus (PV) samples with a low viral-purity level or to study the less abundant sub-viral particles, revealed the necessity for an intra-column signal enhancement strategy. Although intra-column signal enhancement is a very popular approach to assay small molecules, it is less straightforward for the analysis of biological macromolecules or particles. A reason could be that, for a proper signal enhancement approach, these samples have to be thoroughly studied to understand the factors affecting the separation process. For the investigated PV samples, a screening design revealed that injecting larger sample plugs significantly enhanced the analytical signal, but also significantly decreased the separation efficiency. A subsequently executed central composite design determined the largest sample plug that can be injected without compromising the separation. Finally, the sample dilution and the length of the injected plug were used for tuning the intensity of the analytical response. Two combinations of sample dilution and injected plug size, at extreme values, were investigated in detail to define the best procedure for PV analysis using CE. In both situations, PV was effectively separated and quantified in rather complex samples, showing a good repeatability, an acceptable linearity for the PV particles and a decreased limit of detection in comparison with the existing method. In conclusion, intra-column signal enhancement can be successfully applied for viral suspensions, extending the applicability of CE methods to samples with lower virus concentrations, and/or allowing a significant reduction in the minimum required volume of sample. For PV samples, 5µl of sample is necessary instead of the previous 20µl, while the analytical signal was enhanced up to 14 times. The results of this study can provide a basis for the development of routine CE methods for viral particle analysis, especially when rational and reproducible signal enhancement is required.