A simple thin layer chromatography based method for the quantitative analysis of biosurfactant surfactin vis-a-vis the presence of lipid and protein impurities in the processing liquid

TLC- smartphone for ofloxacin and dexamethasone determination in pharmaceutical formulation and rabbit aqueous humor

Preserving the environment and reducing the harmful effects of chemicals on it, is a primary goal of the research, nowadays. One of the major challenges for research is assessing the efficiency and quality of the proposed method in terms of environmental and human safety, as well as their overall cost. Thin layer chromatography (TLC)-Smartphone is a simple, cost-effective, and rapid method for the detection and quantification of analytes. This work describes the development of a green, white, sensitive and easy TLC method that employs a smartphone charge-coupled device (CCD) camera for image acquisition that provides data regarding the identity and quantity of ofloxacin (OFL) and dexamethasone (DEXA) in their mixture. A mixture of OFL and DEXA was separated on a silica gel 60 F254 plate using a mobile phase of n-butanol: acetic acid: water (6:2:2, by volume). Visualization of the separated spots was achieved using the "Universal Stain" iodine vapor (I2) and potassium permanganate (KMnO4), resulting in colored spots on the TLC plate. The Rf values of ofloxacin (0.25) and dexamethasone (0.8) were determined from the recorded images, enabling the identification of the drugs. It was possible to construct a linear calibration model and relate optical density with concentration per band. A linear calibration model was constructed to correlate optical density with concentration per band. A smartphone application was developed to calculate the spot intensity, which was then used to quantify ofloxacin and dexamethasone in their mixture. The TLC-Smartphone method produced linear calibration curves between the color intensity of each spot and the corresponding concentrations. For iodine vapor visualization, the linearity range was 10-50 μg/band for ofloxacin and 40-120 μg/band for dexamethasone. For KMnO4 visualization, the linearity was in the range of 10-50 μg/band for both drugs. The proposed method was validated following ICH guidelines, and was successfully applied for the estimation of ofloxacin and dexamethasone in their eye drop pharmaceutical form and rabbit aqueous humor.

Native Bacillus paralicheniformis isolate as a potential agent for phytopathogenic nematodes control

Phytopathogenic nematodes (PPNs) are responsible for substantial damages within agricultural crops worldwide which can be controlled employing beneficial microorganisms and/or their metabolites in an ecofriendly way. Nevertheless, the success of the control regards not only on the virulence of the strains or the toxicity of their metabolites but also on their ability to colonize and remain in the rhizospheric environment, particularly in those crops affected by abiotic stresses promoted by the climate change. Consequently, the bioprospection of beneficial microorganisms able to control PPNs and to thrive in adverse conditions has attracted attention. On this way, deserts are perfect ecological niches to isolate microorganisms adapted to harsh enviroments. The purpose of this research was to isolate and characterize bacteria from rhizospheric soil samples collected in the Northwestern Desert of Mexico with potential for PPNs control. As first screening, secretomes of each isolate were tested in vitro for nematicidal activity (NA). Then, activities from secretomes and endospores from the selected isolate were confirmed in vivo assays. From 100 thermotolerant isolates, the secretome of the isolate identified as Bacillus paralicheniformis TB197 showed the highest NA (>95%) against Meloidogyne incognita, both in vitro and in vivo tests, suppressing infections caused by M. enterolobii in tomato crops, too. In open field tests, the endospores of TB197 strain showed a reduction of 81% in the infection severity caused by M. enterolobii (p ≤ 0.05), while the galling index (GI) was reduced 84% (p ≤ 0.05) in tomato greenhouse-tests. Also, a reduction of the root necrosis (81%) caused by Radopholus similis in banana plantations (p ≤ 0.05), compared to the control was observed. Owing to their efficacy in controlling PPNs infections, the endospores and secondary metabolites of B. paralicheniformis TB197 strain could be used in bionematicidal formulations.

Nematicidal lipopeptides from Bacillus paralicheniformis and Bacillus subtilis: A comparative study

The aim of this work was to develop a comparative study between Bacillus paralicheniformis TB197 and B. subtilis ATCC 21332 strains in terms of growth, cyclic lipopeptide production, nematicidal activity, and active lipopeptide characteristics. Crude lipopeptide extracts (CLEs) from their fermentation broths were obtained, and their nematicidal activity (NA) was estimated as the mean lethal dose (LD₅₀), employing Caenorhabditis elegans. Using a bioguided approach, CLE components were fractionated by semipreparative thin layer chromatography, and active lipopeptides were characterized by mass spectrometry. Both strains produced similar concentrations of CLEs (p ≥ 0.05) (0.99 ± 0.11 and 1.14 ± 0.15 mg/mL by TB197 and ATCC 21332, respectively). The estimated LD₅₀ values of CLEs from the TB197 and ATCC 21332 strains were 3.88 and 8.15 mg/mL, respectively, showing that the NA of the TB197 strain CLE was 2.1-fold higher (p ≤ 0.05). Mass spectrometry revealed that strain TB197 synthesizes several families of lipopeptides, namely, fengycin A (C₁₄-C₁₇), fengycin B (C₁₆-C₁₇), surfactin (C₁₅-C₁₇), and lichenysin (C₁₂, C₁₃, C₁₄, and C₁₆), from which fengycins and lichenysins possess the highest NA (100 and 60% mortality in C. elegans larvae, respectively), while the ATCC 21332 strain produces mainly surfactin (C₁₃-C₁₇) (NA 63% mortality). The main differences found in this study were that the TB197 strain has a higher tolerance to inhibition by the product, and the lipopeptides they synthesize have a higher nematicidal activity due to the diversity of families compared to ATCC 21332. Likewise, it was shown that more polar lipopeptides (fengycins) are more effective at causing mortality in C. elegans larvae. KEY POINTS: • The nematicidal activity of lipopeptides from TB197 is higher than from ATCC 21332 • TB197 produces surfactin, lichenysin, and fengycin, while ATCC 21332 mainly produces surfactin • The most polar lipopeptides (fengycins) cause more mortality in C. elegans L2.