Control of ascorbic acid in fortified powdered soft drinks using near-infrared spectroscopy (NIRS) and multivariate analysis.

Powdered soft drinks (PSDs), fortified with antioxidants such as ascorbic acid (AA), are normally controlled by titration or chromatographic methods. This study evaluated the feasibility of using near-infrared spectroscopy (NIRS) and multivariate analysis to predict AA contents in PSDs as an alternative not-destructive method. The AA content of sixty-seven samples of commercial fortified grape and passion fruit PSDs was analyzed by the standard method (titration) and showed significant variance between flavors within the same brand. In addition, 75% of the samples required from 0.3 to 10.2 more cups of grape than passion fruit flavor to supply the AA Reference Nutrient Intake for children and adults. Spectral and reference data sets were split into calibration and validation sets. Partial least squares regression models were built and validated for the determination of AA in both PSDs. The model's basic statistics for grape flavor PSDs (RMSEC = 0.49 mg g-1, Rcal 2 = 0.84; RMSECV = 0.67 mg g-1, RCV 2 = 0.70; RMSEP = 0.50 mg g-1, Rpred 2 = 0.84), and that for passion fruit flavor PSDs (RMSEC = 0.24 mg g-1, Rcal 2 = 0.95; RMSECV = 0.56 mg g-1, RCV 2 = 0.76; RMSEP de 0.57 mg g-1, Rpred 2 = 0.72) indicated that NIRS-PLS methodology produced reasonable results. The limits of detection and quantification obtained showed that the method is useful to detect and quantify AA in the studied samples. A new set of grape drinks was used for external prediction and the RMSEP was 0.62 mg g-1, Rpred 2 was 0.72. Based on the results, NIRS-multivariate analysis proved to be useful for quality control of AA in commercialized grape and passion fruit in PSDs and a faster, objective and environmentally friendly method alternative to standard methods.

Synthesis, theoretical studies, and effect on the photosynthetic electron transport of trifluoromethyl arylamides.

BACKGROUND: The photosynthetic apparatus is targeted by various herbicides, including several amides such as diuron and linuron. Considering the need for the discovery of new active ingredients to cope with weed resistance, the synthesis of a series of trifluoromethyl aryl amides is herein described whose inhibitory properties were assessed in vitro on the photosynthetic electron transport chain, and in vivo on the growth of a model cyanobacterial strain. Theoretical studies were also carried out. RESULTS: Starting with 1-fluoro-2-nitro-4-(trifluoromethyl) benzene, the preparation of the amides was achieved via a three-step sequence, namely nucleophilic aromatic substitution, reduction with SnCl2 /HCl, and acylation reactions. The measurement of ferricyanide reduction by functionally intact spinach chloroplasts showed that several derivatives are capable of inhibiting the photosynthetic apparatus. The most active amides presented IC50 values close to 1 µmol L-1 , and showed the presence of a 4-bromophenyl group as a common structural feature. The addition of these brominated amides to the culture medium of a model cyanobacterial strain, Synechococcus elongatus PCC 6301, caused various degrees of growth inhibition. Theoretical studies (molecular modeling and quantitative structure-activity relationship) of all amides and their comparison with some known herbicides confirmed these experimental findings and provided more in-depth information about the possible molecular target of these compounds. CONCLUSION: Trifluoromethyl amides herein described, which were shown to act at the PSII level, may represent a novel scaffold to be exploited aiming at the development of new active ingredients for weed control. © 2017 Society of Chemical Industry.

A best​ comprehension about the toxicity of phenylsulfonyl carboxylates in Vibrio fischeri using quantitative structure activity/property relationship methods.

Aromatic sulfones comprise a class of chemicals used in agrochemical and pharmaceutical industries and as floatation and extractant agents in petrochemical and metallurgy industries. In this study, new QSA(P)R studies were carried out to predict the toxicity against Vibrio fischeri of a set of 52 aromatic sulfones. The same approach was used to evaluate the relationship between these endpoint and the water solubility, another important environmental endpoint. The study resulted in models of good statistical quality and mechanistic interpretation with a possible correlation between the two endpoints, but the toxic effect is also likely to depend on other physicochemical properties. The use of the PLS2, a method not commonly used in QSA(P)R studies, also produced models of greater reliability, and the relationship between the two endpoints was reinforced to some degree. These results are useful for better understanding the process by which these compounds exert their environmental toxicity, thus aiding in the development of industrially useful compounds with less potential environmental damage.

Exploring in vivo violacein biosynthesis by application of multivariate curve resolution on fused UV-VIS absorption, fluorescence, and liquid chromatography-mass spectrometry data.

In this work, the application of multivariate curve resolution-alternating least squares (MCR-ALS) is proposed for extracting information from multitechnique fused multivariate data (UV-VIS absorption, fluorescence, and liquid chromatography-mass spectrometry) gathered during the biosynthesis of violacein pigment. Experimental data sets were pretreated and arranged in a row-wise augmented data matrix before their chemometric investigation. Five different chemical components were resolved. Kinetic and spectral information about these components were obtained and their relationship with violacein biosynthesis was established. Three new chemical compounds with molar masses of 453, 465, and 479 u, until now not reported in the literature, were identified and proposed as intermediates in the biosynthesis of other indolocarbazoles. The precursor (tryptophan), one intermediate (deoxyviolacein), and the final product (violacein) of violacein biosynthesis were identified and characterized using the proposed approach. The chemometric procedure based on the MCR-ALS method has proved to be a powerful tool to investigate violacein biosynthesis and its application can be easily extended to the study of other bioprocesses.

Digital Filters for Molecular Interaction Field Descriptors.

Descriptor properties are often neglected when building 3D-QSAR models. The relevance of correlation and distribution profiles is tested in terms of the models' prediction power. A different approach to filter descriptors prior to variable selection is proposed. Additionally, a protocol for molecular interaction field descriptors selection and model validation is presented. The algorithms and protocols presented are quite simple and enable a different and powerful way to create parsimonious interaction field-based models.

Theoretical study of acid-catalyzed hydrolysis of epoxides.

A theoretical study of propylene oxide acid-catalyzed hydrolysis was performed by investigation of the S(N)1 and S(N)2-like mechanisms. By using chemometric tools, hierarchical cluster analysis (HCA), and principal component analysis (PCA), the MP2/6-311++G** level of theory was selected from HF, MP2, and DFT as the best method to describe the geometry of the basic skeleton (oxirane). At this level of theory, geometry optimizations, vibrational frequencies, intrinsic reaction coordinate (IRC), and other thermodynamic calculations have shown that the borderline S(N)2 mechanism is more favorable than pure S(N)2 and S(N)1 mechanisms in the gas phase. In the S(N)1 mechanism, the existence of the typical carbocation was not observed, and furthermore, the possibility of epoxide conversion to a protonated aldehyde was indicated, even in the presence of a water molecule (nucleophile). The Chelpg charge distribution of the reactants, steric hindrance, synchronous bond breaking-formation and trajectory angle of nucleophilic attack are discussed for pure and borderline S(N)2 mechanisms. Solvation effect calculations indicate that the pure S(N)2 mechanism is more favorable than borderline S(N)2 and S(N)1 mechanisms. This is discussed in terms of hydrogen bond formation.

Multivariate QSAR study of 4,5-dihydroxypyrimidine carboxamides as HIV-1 integrase inhibitors.

A multivariate QSAR study of thirty-three 4,5-dihydroxypyrimidine carboxamides as HIV-1 integrase (HIV-1 IN) inhibitors was performed employing Ordered Predictors Selection (OPS) algorithm and PLS regression for variable selection and model construction, respectively. Four descriptors were chosen and a reasonable model (n=30; R(2)=0.68; SEC=0.57; PRESS(cal)=8.72; F((2,27))=28.97; Q(2)(LOO)=0.58; SEV=0.62; PRESS(val)=11.62; R(2)(pred)=0.87; SEP=0.29; ARE(pred)=4.37%; k=0.99; k'=1.01; |r(2)(0)-r(2)(0)'|=-0.18) was built with two latent variables (59.54% of the information). Leave-N-out (LNO) and Y-randomization methods confirmed the model robustness. The descriptors indicated that the HIV-1 IN inhibition depends on the electronic distribution of the investigated compounds. The interpretation of the model is related to the most accepted mechanism of action.

A quantum chemical and statistical study of flavonoid compounds (flavones) with anti-HIV activity.

The molecular orbital semi-empirical method AM1 was employed to calculate a set of molecular properties (variables) of 22 flavonoid compounds (flavones) with anti-HIV-1 activity and nine new compounds were proposed for anti-HIV-1 activity prediction. Pattern recognition techniques, principal component analysis (PCA), hierarchical cluster analysis (HCA), stepwise discriminant analysis (SDA) and K-nearest neighbor (KNN), were employed in order to reduce dimensionality and investigate which subset of variables could be more effective for classifying the flavones according to their degree of anti-HIV-1 activity. The PCA, HCA, SDA and KNN studies showed that the variables log P (partition coefficient), molecular volume (VOL) and electron affinity (EA) are responsible for the separation between anti-HIV-1 active and inactive compounds. The prediction study was done with a new set of nine analog compounds by using the PCA, HCA, SDA and KNN methods and only one of them was predicted as active against HIV-1.

Spectrophotometric determination of caramel content in spirits aged in oak casks.

A new methodology was developed for determination of caramel in spirits aged in oak casks. The method is based on differences between the electronic spectra of oak aqueous alcoholic extracts and caramel solutions in the same solvent. The data were treated by 2 different approaches: the simplest one was based on the plot of caramel concentration versus the ratio of absorbance at 210 and 282 nm; the other was based on a partial least squares (PLS) calibration model using the first derivative of the spectral data. Both methodologies were applied to analysis of 159 aged spirit samples. The mean caramel content of several Brazilian sugar cane spirits (cachaça) and all United States whiskies was smaller than that of Scottish whiskies and other brandies from several countries. Correlation was good between caramel concentrations for the same sample calculated by the 2 methods. The uncertainties following PLS and the absorbance ratio method were 0.01 and 0.03 g/L, respectively, for a sample containing 0.45 g/L caramel. Treatment of UV-VIS spectra by pattern recognition using hierarchical clustering analysis and principal components analysis allowed discrimination of the samples as a function of their caramel content. It was possible to distinguish U.S. whiskies from other whiskies, but a clear differentiation among Brazilian cachaças as a function of their geographic origin was not feasible. Small caramel quantities as low as 0.08 g/L were clearly detected by these methodologies.