Structure-based virtual screening and molecular dynamics simulation studies to discover new SARS-CoV-2 main protease inhibitors

Computational methods were used to filter two datasets (> 8,000 compounds) based on two criteria: higher binding affinity for M^PRO than cocrystallized inhibitor and binding interactions with M^PRO catalytic dyad (Cys145 and His41). After virtual screening involving ranking and reranking, eleven compounds were identified to satisfy these criteria and analysis of their structures revealed an unparallel common features among them which could be critical for their interactions with M^PRO. However, only the topmost scoring compound (AV-203: K_i = 0.31 µM) exhibited relatively stable binding interaction during the period of 50 ns MD simulation and thus is a suitable template for drug development.

Antitrypanosomal potentials of the extract and fractions of Abrus precatorius seeds

OBJECTIVE

To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice.

METHODS

Parasiteamia was induced unto mice by intraperitoneal injection of 1.25×10(5)Trypanosoma in normal saline. Five days when a high level of parasiteamia was established treatment commenced until ten days. The mice were treated with 10, 20 and 40 mg/kg bt. of the extract and 5 and 10 mg/kg bt. of the fraction (F(2)), respectively for 5 days. Diminazene aceturate at the dose of 3.5 mg/kg bt. for two days was used as the reference drug. The level of parasitaemia and packed cell volume (PCV) of the animals estimated.

RESULTS

At doses of 10, 20 and 40 mg/kg the crude extract showed a sharp reduction in the level of parasitaemia in mice compared with the untreated group. The mice treated with F(2) at doses of 5 and 10 mg/kg showed a sharp reduction in the level of parasitamia to zero in day 9, and a gradual recovery from the 12th day of treatment. This effect is comparable to that of the mice treated with 7 mg/kg of standard drug diminazene aceturate. The PCV of the treated showed a gradual decrease with time, but not as much as the untreated group. Phytochemical screening revealed the presence of glycosides, alkaloids, carbohydrates, tannins and proteins in the Abrus precatorius powder while F(2) was rich in alkaloids.

CONCLUSIONS

This study shows that both the extract and the fractions of Abrus precatorius seeds exhibited a promising trypanocidal property. Alkaloids may be responsible for the observed activity.

In vitro and in vivo evaluation of the antitrypanosomal activity of fractions of Holarrhena africana

The aqueous extract of young leaves of Holarrhena africana, a plant used in the Nigerian traditional medicine, exhibited good activity against Trypanosoma brucei spp. The extract was fractionated and eight fractions were obtained. One fraction designated as HaF(5) showed in vitro activity against Trypanosoma brucei rhodesiense with an IC(50) value of 0.785 microg/mg and no overt cytotoxicity against L-6 cells. Fraction HaF(5) was tested in vivo at two doses and found to exhibit in vivo efficacy in Trypanosoma brucei brucei infected mice leading to a complete disappearance of parasitaemia followed by a relapse.

Antimicrobial activities of some amino derivatives of 5, 7-dibromo-2-methyl-8-benzoyloxyquinoline

In an attempt to design and synthesize more potent quinoline-based chemotherapeutic agents structural modifications of 5, 7-Dibromo-2-methyl-8-benzoyloxyqinoline was carried out. The replacement of the bromine atoms with the requisite alkylamino compound gave four amino-derivatives viz: bis(dipropylamino)-dipyrrolidino-, dipiperidino- and dipiperazino derivatives. The antimicrobial activities of these compounds were investigated against selected Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Escherichin coli, Pseudomonas aeruginosa and Klebsiella spp) and yeast (Candida albicans). All the compounds showed broad or significant antimicrobial activity, which varied from two to ninety times that of the parent compound. The dipyrrolidino derivative was the most effective against Gram-positive bacteria and yeast while the dipiperidino derivative was the most effective against Gram-negative bacteria. No correlation has been established between the minimum inhibitory, (MIC) concentrations of the derivatives and the structural modifications.