Noemí Waksman de Torres

Antimicrobial and Antioxidant Activities of Plants from Northeast of Mexico

Traditional medicine has a key role in health care worldwide. Obtaining scientific information about the efficacy and safety of the plants from our region is one of the goals of our research group. In this report, 17 plants were selected and collected in different localities from northeast Mexico. The dried plants were separated into leaves, flowers, fruit, stems, roots and bark. Each part was extracted with methanol, and 39 crude extracts were prepared. The extracts were tested for their antimicrobial activity using three Gram-negative bacterial strains (Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii), three Gram-positive bacterial strains (Enterococcus faecalis and two Staphylococcus aureus strains), and seven clinically isolated yeasts (Candida albicans, C. krusei, C. tropicalis, C. parapsilosis and C. glabrata); their antioxidant activity was tested using a DPPH free radical assay. No activity against Gram-negative bacteria was observed with any extract up to the maximum concentration tested, 1000 μg ml−1. We report here for the first time activity of Ceanothus coeruleus against S. aureus (flowers, minimal inhibitory concentration (MIC) 125 μg ml−1), C. glabrata (MICs 31.25 μg ml−1) and C. parapsilosis (MICs between 31.25 and 125 μg ml−1); Chrysanctinia mexicana against C. glabrata (MICs 31.25 μg ml−1); Colubrina greggii against E. faecalis (MICs 250 μg ml−1) and Cordia boissieri against C. glabrata (MIC 125 μg ml−1). Furthermore, this is the first report about antioxidant activity of extracts from Ceanothus coeruleus, Chrysanctinia mexicana, Colubrina greggii and Cyperus alternifolius. Some correlation could exist between antioxidant activity and antiyeast activity against yeasts in the species Ceanothus coeruleus, Schinus molle, Colubrina greggii and Cordia boissieri.

Multi-wavelength high-performance liquid chromatographic fingerprints and chemometrics to predict the antioxidant activity of Turnera diffusa as part of its quality control.

The determination of the antioxidant activity of Turnera diffusa using partial least squares regression (PLSR) on chromatographic data is presented. The chromatograms were recorded with a diode array detector and, for each sample, an enhanced fingerprint was constructed by compiling into a single data vector the chromatograms at four wavelengths (216, 238, 254 and 345 nm). The wavelengths were selected from a contour plot, in order to obtain the greater number of peaks at each of the wavelengths. A further pretreatment of the data that included baseline correction, scaling and correlation optimized warping was performed. Optimal values of the parameters used in the warping were found by means of simplex optimization. A PLSR model with four latent variables (LV) explained 52.5% of X variance and 98.4% of Y, with a root mean square error for cross validation of 6.02. To evaluate its reliability, it was applied to an external prediction set, retrieving a relative standard error for prediction of 7.8%. The study of the most important variables for the regression indicated the chromatographic peaks related to antioxidant activity at the used wavelengths.

Activity against Streptococcus pneumoniae of the Essential Oil and δ-Cadinene Isolated from Schinus molle Fruit

Abstract Streptococcus pneumoniae is a major cause of respiratory infections. This study aims to test the activity of the essential oil obtained from the fruit of Schinus molle against S. pneumoniae resistant to conventional antibiotics and to identify the compounds responsible for the activity. A fraction showing antimicrobial activity (MIC 125 μg/mL) was obtained. The principal components were identified as: β-myrcene (39.7%), p-cymene (19.5%), δ-cadinene (7.8%), α-phellandrene (7.1%) and limonene (4.1%). Bioassay-guided fractionation led to the identification of δ-cadinene as the principal active constituent (MIC of 31.25 μg/mL). The findings reported here highlight and justify the global spread of the use of S. molle for the treatment of respiratory infections.

Correlation between Chromatographic Fingerprint and Antioxidant Activity of Turnera diffusa (Damiana)

In the present contribution, the partial least squares (PLS) method was used to establish a correlation between the antioxidant activity (obtained by DPPH assay) and chromatographic profiles of TURNERA DIFFUSA extracts. Chromatograms were obtained using HPLC-DAD. A model was constructed using 40 samples with 2550 X variables corresponding to the responses obtained at different times; the Y variables consisted of experimental values of antioxidant activity of each extract (measured as EC₅₀). Prior to this analysis, alignment of chromatograms was performed based on consideration of seven high-intensity signals present in all samples. The PLS1 model was validated by cross-validations; its capacity was evaluated using correlation parameters R², root mean square error of calibration (RMSEC), and root mean square error of prediction (RMSEP). The best results were achieved with zero order chromatograms using five-point smoothing (R² = 0.96, RMSEC = 3.31, and RMSEP = 7.86). Under these conditions, the optimal number of components was five. The model was applied to the prediction of antioxidant activity of commercial products; no significant differences were found between the experimental and predicted antioxidant activities for 83 % of them.

Solid‐Phase Microextraction Followed by High‐Performance Liquid Chromatography with Fluorimetric and UV Detection for the Determination of Polycyclic Aromatic Hydrocarbons in Water

Abstract We have developed a solid‐phase microextraction procedure for polycyclic aromatic hydrocarbons. A simplex experimental design was employed to optimize the process. A polydimethylsiloxane/divinylbenzene fiber was selected. The optimum conditions were: an extraction step in the immersion mode, over a period of 60 min at 70°C using high‐speed stirring, and an 8 min desorption step using acetonitrile (90 µl). Linear relationships were obtained for all compounds, except for naphthalene. Our method showed a good precision and accuracy with a detection limit between 0.005 and 0.306 µg l−1. Our method was used to detect PAHs in real water samples.

Development of a Spectrofluorimetric Method for the Determination of Gatifloxacin in Semen

Abstract Gatifloxacin is an 8‐methoxyfluoroquinolone, which shows strong activity against a wide variety of microorganisms. It has been applied for the treatment of male genital tract infections caused by Chlamydia and Mycoplasma species, which are found in many men with asymptomatic infertility. The aim of this study was to develop and validate an analytical spectrofluorimetric method to quantify gatifloxacin in semen. Determination was carried out at pH 3.0, using 300 nm and 486 nm as excitation and emission wavelengths, respectively. The detection and quantification limits were 0.06 and 0.2 µg/mL, respectively. The precision of the method expressed as the relative standard deviation (RSD) was 1.3% and the efficiency of recovery was in the range of 62%–72%. This method is fast, easy to perform, and allows the quantification of gatifloxacin in the semen of patients during treatment for genital tract infections; it could also be used with other biological fluids (serum, urine), after optimizing the test conditions.

Synthesis of Leubethanol derivatives and evaluation against Mycobacterium tuberculosis

Twenty-five derivatives of the natural diterpene leubethanol, including several potential pro-drugs, with changes in the functionality of the aliphatic chain or modifications of the phenolic group, were synthesized and tested in vitro by the MABA technique for their activity against the H37Rv strain of Mycobacterium tuberculosis. Several compounds showed antimycobacterial potencies similar to that of the lead compound and two of them displayed higher selectivity indexes.

Larvicidal and cytotoxic activities of extracts from 11 native plants from northeastern Mexico.

ABSTRACT Of all mosquito-borne viral diseases, dengue is spreading most rapidly worldwide. Conventional chemical insecticides (e.g., organophosphates and carbamates) effectively kill mosquitoes at their larval stage, but are toxic to humans. Natural product-based insecticides may be highly specific. Herein, we report the insecticidal activities of 11 native Mexican plants against Aedes aegypti (L). Ether extracts of Ambrosia confertiflora De Candolle, Thymus vulgaris (L.), and Zanthoxylum fagara (L.), and both ether and methanol extracts of Ruta chalepensis L. were significantly larvicidal toward the dengue mosquito after 24 h of exposure. Of them, only the ether extract of A. confertiflora was toxic to Vero cells. In conclusion, the ether extracts of Thymus vulgaris, Z. fagara, and both ether and methanol extracts of Ruta chalepensis L., could be considered as potential bioinsecticides.

Simultaneous Determination of Anticonvulsants and Their Principal Metabolites by HPLC

Abstract A rapid, precise, and sensitive method has been developed for the simultaneous determination of five antiepileptic drugs (carbamazepine, phenobarbital, diphenylhydantoin, primidone, and oxcarbazepine) and six metabolites (from carbamazepine, carbamazepin‐10,11‐epoxide; from phenobarbital, p‐hydroxyphenobarbital; from primidone, 2‐phenyl‐2‐ethylmalonamide; from diphenylhydantoin, 5‐(p‐hydroxyphenyl)‐5‐phenylhydantoin) in human serum. Separation was achieved by means of liquid chromatography with a diode array detector (DAD) using reverse‐phase ODS‐Hypersil columns (100 × 2.1 mm) with particle size of 5 µm, flow‐rate 0.6 mL/minute, column temperature 40°C, wavelength: 210 nm. Mobile phase was a gradient consisting of solvent A: phosphate buffer pH 5.7, solvent B: MeOH. Two procedures were tested for the serum treatment: protein precipitation with acetonitrile and solid‐phase extraction with C18 cartridges. The best recoveries were found by means of protein precipitation. Solid‐phase extraction gave poor recoveries for phenobarbital and its metabolite. The results obtained are suitable in terms of precision, linearity, and accuracy for the simultaneous determination of serum levels of the mentioned drugs in the usual therapeutic ranges.

Diterpenes Synthesized from the Natural Serrulatane Leubethanol and Their in Vitro Activities against Mycobacterium tuberculosis

Seventeen new derivatives of the natural diterpene leubethanol, including some potential pro-drugs, with changes in the functionality of the aliphatic chain or modifications of aromatic ring and the phenolic group, were synthesized and tested in vitro by the MABA technique for their activity against the H37Rv strain of Mycobacterium tuberculosis. Some compounds showed antimycobacterial selectivity indices higher than leubethanol.