Ilimaquinone (marine sponge metabolite) as a novel inhibitor of SARS-CoV-2 key target proteins in comparison with suggested COVID-19 drugs: designing,docking and molecular dynamics simulation study

The outbreak of novel coronavirus, SARS-CoV-2, has infected more than 36 million people and caused approximately 1 million deaths around the globe as of 9 October 2020. The escalating outspread of the virus and rapid rise in the number of cases require the instantaneous development of effectual drugs and vaccines. Presently, there are no approved drugs or vaccine available to treat the infection. In such scenario, one of the propitious therapeutic approaches against viral infection is to explore enzyme inhibitors amidst natural compounds, utilizing computational approaches aiming to get products with negligible side effects. In the present study, the inhibitory prospects of ilimaquinone (marine sponge metabolite) were assessed in comparison with hydroxychloroquine, azithromycin, favipiravir, ivermectin and remdesivir at the active binding pockets of nine different vital SARS-CoV-2 target proteins (spike receptor binding domain, RNA-dependent RNA polymerase, Nsp10, Nsp13, Nsp14, Nsp15, Nsp16, main protease, and papain-like-protease), employing an in silico molecular interaction based approach. In addition, molecular dynamics (MD) simulations of the SARS-CoV-2 papain-like protease (PLpro)–ilimaquinone complex were also carried out to calculate various structural parameters including root mean square fluctuation (RMSF), root mean square deviation (RMSD), radius of gyration (R_g) and hydrogen bond interactions. PLpro is a promising drug target, due to its imperative role in viral replication and additional function of stripping ubiquitin and interferon-stimulated gene 15 (ISG15) from host-cell proteins. In light of the possible inhibition of all vital SARS-CoV-2 target proteins, our study has emphasized the importance to study in depth ilimaquinone actions in vivo.

Inhibitory potential of ilimaquinone (marine sponge metabolite) against nine essential SARS-CoV-2 target proteins, employing a molecular interaction and dynamics simulation approach.     

Design and formulation of polymeric nanosponge tablets with enhanced solubility for combination therapy

Three drugs namely caffeine, paracetamol, and aceclofenac are commonly used for treating various acute and chronic pain related ailments. These 3 drugs have varied solubility profiles, and formulating them into a single tablet did not have the desired dissolution profile for drug absorption. The objective of the present research was to tailor the drug release profile by altering drug solubility. This was achieved by loading the drug into nanosponges. Here, three-dimensional colloidal nanosponges were prepared using β-cyclodextrin with dimethyl carbonate as a cross-linker using the hot-melt compression method. The prepared nanosponges were characterized by FTIR, ¹H NMR spectroscopy, DSC, XRPD studies and SEM. The FTIR and DSC results obtained indicated polymer-drug compatibility. The ¹H NMR spectroscopy results obtained indicated the drug entrapment within nanosponges with the formation of the inclusion complex. XRPD studies showed that the loaded drug had changed crystalline properties altering drug solubility. SEM photographs revealed the porous and spongy texture on the surface of the nanosponge. Box–Behnken experimental design was adopted for the optimization of nanosponge synthesis. Among the synthesized nanosponges containing paracetamol, aceclofenac and caffeine, batch F3–P31, F3–A31 and F3–C31 were considered optimized. Their particle size was 185, 181 and 199 nm with an entrapment efficiency of 81.53, 84.96, and 89.28% respectively. These optimized nanosponges were directly compressed into tablets and were studied for both pre and post-compression properties including in vitro drug release. The prepared tablet showed desired drug dissolution properties compared to the pure drug. The above outcomes indicated the applicability of nanosponges in modulating the drug release with varied solubility for combination therapy.

Polymeric nanosponges as potential carriers for successful combination therapy of poorly soluble drugs (paracetamol, aceclofenac, caffeine).     

Interaction between the opposing functional effects of cyclic AMP and cyclic GMP in hypertrophic cardiac myocytes

We tested the hypothesis that in isolated cardiac myocytes, the negative functional effects of cyclic GMP would be blunted when the level of cyclic AMP was increased and that this interaction would be altered in renal hypertensive (One-Kidney-One-Clip, 1K1C) cardiac hypertrophic rabbits. Using isolated control and 1K1C ventricular myocytes, cyclic AMP and cell shortening (%) data were collected: 1) at baseline, 2) after the addition of 8-Br-cGMP 10^{−7, −6, −5} M, and 3) after forskolin (10⁻⁶ M), and adenylate cyclase activator, followed by 8-Br-cGMP 10^{−7, −6,−5} M. Basal levels of cyclic AMP were similar in control vs. 1K1C myocytes (10.2 ± 1.6 vs. 11.3 ± 2.6 pmol/10⁵ myocytes). We found that 8-Br-cGMP decreased the percent shortening in a dose related manner in both control myocytes (5.1 ± 0.6 to 3.2 ± 0.4%) and hypertrophic myocytes (5.2 ± 0.4 to 3.6 ± 0.5). The level of cyclic AMP significantly increased after the addition of 8-Br-cGMP in control myocytes (14.1 ± 2.1), but not in 1K1C myocytes. Forskolin increased the percent shortening in the control myocytes (3.8 ± 0.1 to 4.8 ± 0.4), but no significant increase was noted in the hypertrophic myocytes (3.6 ± 0.3 to 3.7 ± 0.3). The level of cyclic AMP significantly increased after the addition of forskolin in both control (13.9 ± 2.0), and 1K1C cells (14.6 ± 3.8). Forskolin attenuated the negative functional effects of 8-Br-cGMP in the control (4.8 ± 0.4 to 3.2 ± 0.1) and 1K1C myocytes (3.7 ± 0.3 to 2.7 ± 0.3). The adition of 8-Br-cGMP did not affect the level of cyclic AMP after forskolin in either control (13.9 ± 2.0 to 14.8 ± 2.5) or 1K1C myocytes (14.6 ± 3.8 to 13.8 ± 1.9). These data indicated that in hypertrophic cardiac myocytes the negative functional effects of 8-Br-cGMP were similar to control, but the positive functional effects of cyclic AMP were blunted. There was an increase in cyclic AMP levels after addition of 8-Br-cGMP in control but not 1K1C cells. We conclude that in control and hypertrophic myocytes, the effects of cyclic GMP were blunted after forskolin, but this did not seem to be related to cyclic AMP phosphodiesterase activity. Received: 12 October 1999, Returned for 1. revision: 24 November 1999, 1. Revision received: 23 March 2000, Returned for 2. revision: 26 May 2000, 2. received: 16 June 2000, Accepted: 12 July 2000     

Larvicidal and pupicidal activities of ecbolin A and ecbolin B isolated from Ecbolium viride (Forssk.) Alston against Culex quinquefasciatus Say (Diptera: Culicidae)

The mosquitocidal activity of different fractions and isolated compounds from the ethyl acetate extract of Ecbolium viride root was assessed on larvae and pupae of Culex quinquefasciatus Say (Diptera: Culicidae). The larvae and pupae were exposed to concentrations of 6.125, 12.5, 25 and 50 ppm for fractions and 1, 2.5, 5 and 10 ppm for compound. Among the 12 fractions screened, fraction 6 from the ethyl acetate extract of E. viride was recorded to have the highest larvicidal and pupicidal activities against C. quinquefasciatus. The lethal concentration (LC₅₀ and LC₉₀) values of fraction 6 were 4.26 and 9.0 ppm against C. quinquefasciatus larvae and 6.55 and 12.19 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Fraction 7 was recorded to have moderate activity with LC₅₀ and LC₉₀ values of 11.25 and 25.02 ppm against C. quinquefasciatus larvae and 13.33 and 31.15 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Ecbolin A and ecbolin B were identified from fractions 7 and 6, respectively. The structure of the isolated compounds was identified on the basis of spectral data (¹H NMR and ¹³C NMR) and compared with literature spectral data. Further, the isolated compound, ecbolin B, from fraction 6 was recorded to have strong larvicidal and pupicidal activities than ecbolin A. The LC₅₀ and LC₉₀ values of ecbolin B on C. quinquefasciatus larvae were 1.36 and 2.76 ppm, and on pupae, these were 1.54 and 3.51 ppm, respectively. The present results suggest that ecbolin B could be used as a mosquitocidal agent against C. quinquefasciatus.     

A multi‐centre,single‐arm,open‐label study evaluating the safety and efficacy of fixed dose rituximab in patients with refractory,relapsed or chronic idiopathic thrombocytopenic purpura (R‐ITP1000 study)

The efficacy of a fixed‐dose rituximab schedule was prospectively explored in primary/acute refractory, relapsed or chronic (platelet count >10 × 10⁹/l and ≤50 × 10⁹/l) idiopathic thrombocytopenic purpura (ITP). Patients received two doses of rituximab (1000 mg) on days 1 and 15 and were followed‐up on weeks 1–8, 12, 26, 39 and 52. A total of 122 patients were included in the safety population; efficacy was analysed in 108 patients. Overall response rate (ORR) at week 8, defined as the proportion of patients achieving complete response (CR; platelet count >150 × 10⁹/l) or partial response (PR; platelet count >50 × 10⁹/l) was 44%. Therapeutic response, defined as achieving a response at week 8, with at least a minor response (MR; platelet count >30 × 10⁹/l), sustained up to weeks 26 and 52 and accompanied by a reduction in ITP medications, was achieved in 44% (week 26) and 35% (week 52) of patients, respectively. Treatment was well tolerated with no safety concerns. While this study failed to meet its primary endpoint of an ORR of 50%, the efficacy of two fixed doses of rituximab appear to provide similar efficacy to the standard 375 mg/m² four‐dose schedule in relapsed/chronic ITP.