Validated High-Performance Thin-Layer Chromatography-Mass Spectrometry Method and Stability Study of Linalool in the Volatile Oil of the Rhizomes of Homalomena aromatica Schott.

Homalomena aromatica is a herb of tremendous ethnomedicinal importance to various communities residing in northeast India. In this study, a high-performance thin-layer chromatography-based densitometric method was developed for identification, quantification and stability study of linalool. Mass spectrometry was hyphenated to HPTLC for streamlining the method. The stability of linalool was studied by analyzing the effect of acid, base, UV, sunlight, thermal stress and H2O2 on linalool. The chromatographic plates were developed to a height of 70 mm in toluene:ethyl acetate solvent system at a ratio of 9.5:0.5 and visualized with p-anisaldehyde reagent. The developed method was found to be precise, accurate and reproducible according to International Conference on Harmonization guidelines, and compact bands of linalool were observed at Rf of 0.351 ± 0.001. The content of linalool in the volatile oil of H. aromatica was found to be 58% v/v. By application of the hyphenated MS technique, linalool was identified at m/z 137, (M + H)+. It was observed that acidic pH has the highest effect on linalool with a percentage degradation of 65. The developed method can be used in the analysis and quality control of herbal materials and volatile oils containing linalool and quality control of rhizomes of H. aromatica.

Integrated computational approach towards repurposing of antimalarial drug against SARS-CoV-2 main protease.

Huge vaccination drives are underway around the world for the ongoing COVID-19 pandemic. However, the search for antiviral drugs is equally crucial. As new drug discovery is a time-consuming process, repurposing of existing drugs or developing drug candidates against SARS-CoV-2 will make the process faster. Considering this, 63 approved and developing antimalarial compounds were selected to screen against main protease (Mpro) and papain-like protease (PLpro) of SARS-CoV-2 using in silico methods to find out possible new drug candidate(s). Out of 63 compounds, epoxomicin showed the best binding affinity against the Mpro with CDocker energy of - 57.511 kcal/mol without any toxic effect. This compound was further taken for molecular dynamic simulation study, where the Mpro-epoxomicin complex was found to be stable with binding free energy - 79.315 kcal/mol. The possible inhibitory potential of the selected compound was determined by 3D-QSAR analysis and found to be 0.4447 µM against SARS-CoV-2 Mpro. Finally, the structure activity relationship of the compound was analyzed and two fragments responsible for overall good binding affinity of the compound at the active site of Mpro were identified. This study suggests a safe antimalarial drug, namely epoxomicin, as a probable inhibitor of SARS-CoV-2 Mpro which needs further validation by in vitro/in vivo studies before clinical use. Supplementary Information: The online version contains supplementary material available at 10.1007/s11224-022-01916-0.

In vitro Evaluation and Molecular Dynamics, DFT Guided Investigation of Antimalarial Activity of Ethnomedicinally used Coptis teeta Wall.

BACKGROUND: Malaria is caused by different species of Plasmodium; among which P. falciparum is the most severe. Coptis teeta is an ethnomedicinal plant of enormous importance for tribes of northeast India. OBJECTIVE: In this study, the antimalarial activity of the methanol extracts of Coptis teeta was evaluated in vitro and lead identification was carried out via in silico study. METHODS: On the basis of the in vitro results, in silico analysis by application of different modules of Discovery Studio 2018 was performed on multiple targets of P. falciparum taking into consideration some of the compounds reported from C. teeta. RESULTS: The IC50 of the methanol extract of Coptis teeta was reported to be 0.08 µg/ml in 3D7 strain and 0.7 µg/ml in Dd2 strain of P. falciparum. From the docking study, noroxyhydrastatine was observed to have better binding affinity in comparison to chloroquine. The binding of noroxyhydrastinine with dihydroorotate dehydrogenase was further validated by molecular dynamics simulation and was observed to be significantly stable in comparison to the co-crystal inhibitor. During simulations, it was observed that noroxyhydrastinine retained the interactions, giving strong indications of its effectiveness against the P. falciparum proteins and stability in the binding pocket. From the Density-functional theory analysis, the bandgap energy of noroxyhydrastinine was found to be 0.186 Ha, indicating a favorable interaction. CONCLUSION: The in silico analysis as an addition to the in vitro results provides strong evidence of noroxyhydrastinine as an antimalarial agent.

Computational guided identification of a citrus flavonoid as potential inhibitor of SARS-CoV-2 main protease.

Although vaccine development is being undertaken at a breakneck speed, there is currently no effective antiviral drug for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19. Therefore, the present study aims to explore the possibilities offered by naturally available and abundant flavonoid compounds, as a prospective antiviral drug to combat the virus. A library of 44 citrus flavonoids was screened against the highly conserved Main Protease (Mpro) of SARS-CoV-2 using molecular docking. The compounds which showed better CDocker energy than the co-crystal inhibitor of Mpro were further revalidated by flexible docking within the active site; followed by assessment of drug likeness and toxicity parameters. The non-toxic compounds were further subjected to molecular dynamics simulation and predicted activity (IC50) using 3D-QSAR analysis. Subsequently, hydrogen bonds and dehydration analysis of the best compound were performed to assess the binding affinity to Mpro. It was observed that out of the 44 citrus flavonoids, five compounds showed lower binding energy with Mpro than the co-crystal ligand. Moreover, these compounds also formed H-bonds with two important catalytic residues His41 and Cys145 of the active sites of Mpro. Three compounds which passed the drug likeness filter showed stable conformation during MD simulations. Among these, the lowest predicted IC50 value was observed for Taxifolin. Therefore, this study suggests that Taxifolin, could be a potential inhibitor against SARS-CoV-2 main protease and can be further analysed by in vitro and in vivo experiments for management of the ongoing pandemic.

Development and Validation of High-Performance Thin-layer Chromatographic Method for Quantification of Berberine in Rhizomes of Coptis teeta Wall, an Endangered Species Collected from Arunachal Pradesh, India.

The high polarity of the protoberberine alkaloids present in Coptis teeta has made it difficult to quantify the alkaloids. This study was designed to develop and validate a thin-layer chromatography (TLC) densitometric-based method using high-performance thin-layer chromatography for quantification of berberine. The separation was achieved in a solvent system consisting of butanol:ethyl acetate:formic acid:water by volume on TLC aluminum plate precoated with silica gel 60 F254. Determination and quantification were performed by densitometric scanning under mercury lamp at a wavelength 351 nm in absorbance mode. The validated method gave compact bands for berberine at an Rf of 0.70. The precision, accuracy and reproducibility of the method were validated by following International Conference on Harmonization guidelines. Graphically, linear results were obtained for berberine with correlation coefficient of 0.997 ± 0.09% (R ± SD) in the concentration range of 90-210 ng/band. The limit of quantification and limit of detection from the analysis were found to be 70 and 30 ng/band, respectively. The berberine concentration in the methanol extract of C. teeta was found to be 30.97 ± 0.55 mg in 100 mg of the crude drug. The method developed here in can be implemented in the analysis and routine quality control of herbal materials and formulations containing C. teeta and berberine.