Derek Nexus Research Articles

New structural alerts for Ames mutagenicity discovered using emerging pattern mining techniques

The discovered patterns are used to develop new structural alerts for mutagenicity in the Derek Nexus expert system.

Triterpenic and monoterpenic esters from stems of Ichnocarpus frutescens and their drug likeness potential

Phytochemical studies of ethanolic extract of stems of Ichnocarpus frutescens resulted in the isolation of tetracyclic triterpenic ester lanosteryl oleate (6), two new monoterpenic esters, menth-1(7)-en-9-olyl dodecanoate (7), and 2-(4-methylcyclohex-3-enyl)propyl dodecanoate (8). Their structures were established on the basis of extensive spectral data analysis and chemical methods. From the literature survey, it was revealed that none of these three compounds have been reported earlier from any other parts of I. fructescens. Using StarDrop, drug metabolism and pharmacokinetic parameters have been studied, while data of toxicological endpoints were generated using Derek Nexus. 7 is metabolically stable as compared to 6 and 8. All three molecules are highly lipophilic so tendency to get distributed in brain and adipose tissue is more. Based on the current knowledge database, Derek Nexus predicted that these molecules are not mutagenic, carcinogenic, genotoxic, hepatotoxic, hERG channel inhibitor, nephrotoxic, neurotoxic but StarDrop found them as probable developmental toxic. So in a word, these phytoconstituents have drug-likeness potential and can be evaluated for possible targets.

Derek Nexus predicts human skin sensitisation accurately. What is the rationale behind its predictive performance?

Domiphen bromide and didecyl dimethylammonium bromide were widely used environmental chemicals with potent activity on blockade of human ether-a-go-go related gene (HERG) channels. But the mechanism of their action is not clear. The kinetics of block of HERG channels by domiphen bromide and didecyl dimethylammonium bromide was studied in order to characterize the inhibition of HERG currents by these quaternary ammonium compounds (QACs). Domiphen bromide and didecyl dimethylammonium bromide inhibited HERG channel currents in a dose-dependent manner with IC50 values of 9 nM and 5 nM, respectively. Block of HERG channel by domiphen bromide and didecyl dimethylammonium bromide was voltage-dependent and use-dependent. Domiphen bromide and didecyl dimethylammonium bromide caused substantial negative shift of the activation curves, accelerated activated process, but had no effects on the deactivation and reactivation processes. The docking models implied that these two compounds bound to PAS domain of HERG channels and inhibited its function. Our data demonstrated that domiphen bromide and didecyl dimethylammonium bromide blocked the HERG channel with a preference for the activated channel state.

On the Use of In Silico Tools for Prioritising Toxicity Testing of the Low‐Volume Industrial Chemicals in REACH

This study was conducted to evaluate the utility of a selection of commercially and freely available non-testing tools and to analyse how REACH registrants can apply these as prioritisation tool for low-volume chemicals. The analysis was performed on a set of organic industrial chemicals and pesticides with extensive peer-reviewed risk assessment data. Analysed in silico model systems included Derek Nexus, Toxtree, QSAR Toolbox, LAZAR, TEST and VEGA, and results from these were compared with expert-judged risk classification according to the classifying, labelling and packaging (CLP) regulation. The most reliable results were obtained for carcinogenicity; however, less reliable predictions were derived for mutagenicity and reproductive toxicity. A group of compounds frequently predicted as false negatives was identified. These were relatively small molecules with low structural complexity, for example benzene derivatives with hydroxyl-, amino- or aniline-substituents. A rat liver S9 metabolite simulator was applied to illustrate the importance of considering metabolism in the risk assessment procedure. We also discuss outcome of combining predictions from multiple model systems and advise how to apply in silico tools. These models are proposed to be used to prioritise low-volume chemicals for testing within the REACH legislation, and we conclude that further guidance is needed so that industry can select and apply models in a reliable, systematic and transparent way.

A rapid stability-indicating, fused-core HPLC method for simultaneous determination of β-artemether and lumefantrine in anti-malarial fixed dose combination products

BackgroundArtemisinin-based fixed dose combination (FDC) products are recommended by World Health Organization (WHO) as a first-line treatment. However, the current artemisinin FDC products, such as β-artemether and lumefantrine, are inherently unstable and require controlled distribution and storage conditions, which are not always available in resource-limited settings. Moreover, quality control is hampered by lack of suitable analytical methods. Thus, there is a need for a rapid and simple, but stability-indicating method for the simultaneous assay of β-artemether and lumefantrine FDC products.MethodsThree reversed-phase fused-core HPLC columns (Halo RP-Amide, Halo C18 and Halo Phenyl-hexyl), all thermostated at 30°C, were evaluated. β-artemether and lumefantrine (unstressed and stressed), and reference-related impurities were injected and chromatographic parameters were assessed. Optimal chromatographic parameters were obtained using Halo RP-Amide column and an isocratic mobile phase composed of acetonitrile and 1mM phosphate buffer pH 3.0 (52:48; V/V) at a flow of 1.0 ml/min and 3 μl injection volume. Quantification was performed at 210 nm and 335 nm for β-artemether and for lumefantrine, respectively. In-silico toxicological evaluation of the related impurities was made using Derek Nexus v2.0®.ResultsBoth β-artemether and lumefantrine were separated from each other as well as from the specified and unspecified related impurities including degradants. A complete chromatographic run only took four minutes. Evaluation of the method, including a Plackett-Burman robustness verification within analytical QbD-principles, and real-life samples showed the method is suitable for quantitative assay purposes of both active pharmaceutical ingredients, with a mean recovery relative standard deviation (± RSD) of 99.7 % (± 0.7%) for β-artemether and 99.7 % (± 0.6%) for lumefantrine. All identified β-artemether-related impurities were predicted in Derek Nexus v2.0® to have toxicity risks similar to β-artemether active pharmaceutical ingredient (API) itself.ConclusionsA rapid, robust, precise and accurate stability-indicating, quantitative fused-core isocratic HPLC method was developed for simultaneous assay of β-artemether and lumefantrine. This method can be applied in the routine regulatory quality control of FDC products. The in-silico toxicological investigation using Derek Nexus® indicated that the overall toxicity risk for β-artemether-related impurities is comparable to that of β-artemether API.

Feasibility study of nonclinical safety assessments on homeopathic preparations using the example of protoanemonin in Pulsatilla pratensis L.

Homeopathy is a world-wide available form of complementary therapy, which has a tradition of 200years. Due to the long history of clinical use, i.e. reflected by the first edition of the Homeopathic Pharmacopoeia of the US of 1914, the conduct of toxicological studies is not required if the safety has been otherwise substantiated. The aim of this article is to establish a risk assessment procedure without full toxicological examination, using homeopathic preparations from Pulsatilla pratensis L. as an example. The literature review shows that protoanemonin is the most relevant constituent of these plants regarding potential toxicity. Based on structural alerts protoanemonin is classified as a Cramer class III compound with the threshold of toxicological concern (TTC) of 180μg/day in adults. Neither computer aided toxicology methods (Toxtree and Derek Nexus®) nor a literature search revealed any evidence of genotoxic, carcinogenic or teratogenic potential of protoanemonin. The protoanemonin exposure from a maximum daily dose of a typical homeopathic preparation of P. pratensis L. does not exceed the TTC. The presented method is transparent, reproducible and applicable to other homeopathic substances as a use-case scenario for computational toxicology in order to evaluate an approach for safety assessment of homeopathic medicinal products.