Development and Validation of a New HPLC Method for Quantification of a Novel Antifungal Drug Based on 1,3,4-Thiadiazole and its Impurities

Isolation, development and validation of HPTLC method for the estimation of β-carotene from Gymnosporia senegalensis (Lam.) Loes

The present study is aimed to isolate terpenoids from Gymnosporia senegalensis through analytical and preparative thin-layer chromatography (TLC) and to determine their antioxidant activity using the 2, 2-diphenyl-1- picrylhydrazyl (DPPH) assay and to find out the presence of β-carotene through high-performance thin-layer chromatography (HPTLC). The validation included linearity, limit of detection (LOD), limit of quantification (LOQ), specificity, precision, recovery, and robustness. All the isolated compounds from TLC exhibited significant antioxidant activity. Among all, isolated compounds from leaf showed highest IC50 values. The highest total terpenoid content (TTC) was found 51.6 ± 0.06 in stem, then 49.02 ± 0.01 in bark, and 46.27 ± 0.01 in leaf. DPPH results indicated that leaf-isolated compound 1 (LIC1) showed the highest IC50 at 7.55 ± 0.02 and stem-isolated compound 2 (SIC2) showed the lowest IC50 at 0.616 ± 0.01 among all the isolated compounds of G. senegalensis. HPTLC separation was carried out on aluminium plates pre-coated with silica gel 60 F254 as the stationary phase and n-hexane: ethyl acetate (6:4, v/v) as the mobile phase. Quantification was achieved based on a densitometric analysis of β-carotene in the concentration range of 100-500 ng/band at 254 nm. For the calibration plots, linear regression produced r2 = 0.96450 and Rf = 0.27. The LOD and LOQ were 10.15 and 30.76 ng/mL for HPTLC and relative standard deviation were 137.26 ± 2.03 and 160.43 ± 2.95 (intra-day) and 127.88 ± 2.14 and 157.27 ± 1.90 (inter-day) for 200 and 400 ng/band, respectively. The present study shows the presence of various types of terpenoids through TLC whereas the HPTLC results indicated that the developed methods were accurate and precise. It also shows that the approach is appropriate for its intended use in routine quality control testing of commercially available tablet formulations and drug assay to assist both industries and researchers in making important decisions at a reasonable cost. Moreover, due to the use of a safer and more environmentally friendly mobile phase in comparison to the toxic mobile phases used in recent analytical techniques to estimate β-carotene, this methodology is also secure and sustainable.

An Overview of Advances in the Chromatography of Drugs Impurity Profiling

A systematic literature survey published in several journals of pharmaceutical chemistry and of chromatography used to analyze impurities for most of the drugs that have been reviewed. This article covers the period from 2016 to 2020, in which almost of chromatographic techniques have been used for drug impurity analysis. These chromatography techniques are important in the analysis and description of drug impurities. Moreover, some recent developments in forced impurity profiling have been discussed, such as buffer solutions, mobile phase, columns, elution modes, and detectors are highlighted in drugs used for the study. This primarily focuses on thorough updating of different analytical methods which include hyphenated techniques for detecting and quantifying impurity and degradation levels in various pharmaceutical matrices.

Quantification of a New Antifungal Drug Based on 1,3,4-Thiadiazole by HPLC-ESI/MS: Method Development, Validation and Pharmacokinetic Application

The high sensitive HPLC-ESI/MS method for quantitative determination of a new antifungal drug - 2-[(1Z)-1-(3,5-diphenyl-1,3,4-thiadiazol-2(3Н)-ylidene)methyl]-3,5-diphenyl-1,3,4-thiadiazol-3-ium chloride (TDZ) - was developed and fully validated. TDZ was separated from plasma and urine samples by acetonitrile deproteinization and extraction without time-consuming sample preparation. The reversed-phase high-performance liquid chromatography on Kromasil 100-3.5 C8 column of TDZ in isocratic elution mode using 0.03% trifluoroacetic acid : acetonitrile (65:35, v/v) at a flow rate of 0.2 mL min^-1 was performed. Determination of TDZ was carried out by a positive electrospray ionization in a selected ion monitoring mode for [M⁺]=489 m/z. The method of absolute calibration was used for quantification of TDZ in two concentrations ranges: 100-2500 pg mL^-1 and 2500-30 000 pg mL^-1. The established method showed a good linearity (R=0.999 for both ranges), the limits of determination and quantification were 50 and 100 pg mL^-1, respectively. The Intra- and Inter-day precision values were measured by t-Distribution and Fisher's Exact Test and were in accordance with the regulatory guidance. Low matrix effects and good recovery were found for TDZ. The present method was successfully applied to determine the pharmacokinetic parameters of TDZ by means of intravenous and oral administrations to rats at 5.0 mg kg^-1 and 10.0 mg kg^-1, respectively.

Synthesis, Antifungal Activity, and 3D-QSAR Study of Novel Nopol-Derived 1,3,4-Thiadiazole-Thiourea Compounds

A series of novel nopol derivatives bearing the 1,3,4-thiadiazole-thiourea moiety were designed and synthesized by multi-step reactions in search of potent natural product-based antifungal agents. Their structures were confirmed by FT-IR, NMR, ESI-MS, and elemental analysis. Antifungal activity of the target compounds was preliminarily evaluated by in vitro methods against Fusarium oxysporum f. sp. cucumerinum, Cercospora arachidicola, Physalospora piricola, Alternaria solani, Gibberella zeae, Rhizoeotnia solani, Bipolaris maydis, and Colleterichum orbicalare at 50 µg/mL. All the target compounds exhibited better antifungal activity against P. piricola, C. arachidicola, and A. solani. Compound 6j (R = m, p-Cl Ph) showed the best broad-spectrum antifungal activity against all the tested fungi. Compounds 6c (R = m-Me Ph), 6q (R = i-Pr), and 6i (R = p-Cl Ph) had inhibition rates of 86.1%, 86.1%, and 80.2%, respectively, against P. piricola, much better than that of the positive control chlorothalonil. Moreover, compounds 6h (R = m-Cl Ph) and 6n (R = o-CF3 Ph) held inhibition rates of 80.6% and 79.0% against C. arachidicola and G. zeae, respectively, much better than that of the commercial fungicide chlorothalonil. In order to design more effective antifungal compounds against A. solani, analysis of the three-dimensional quantitative structure-activity relationship (3D-QSAR) was carried out using the CoMFA method, and a reasonable and effective 3D-QSAR model (r2 = 0.992, q2 = 0.753) has been established. Furthermore, some intriguing structure-activity relationships were found and are discussed by theoretical calculation.