Natural products from Streptomyces spp. as potential inhibitors of the major factors (holoRdRp and nsp13) for SARS-CoV-2 replication: an in silico approach.

The COVID-19 pandemic caused unprecedented damage to humanity, and while vaccines have been developed, they are not fully effective against the SARS-CoV-2 virus. Limited targeted drugs, such as Remdesivir and Paxlovid, are available against the virus. Hence, there is an urgent need to explore and develop new drugs to combat COVID-19. This study focuses on exploring microbial natural products from soil-isolated bacteria Streptomyces sp. strain 196 and RI.24 as a potential source of new targeted drugs against SARS-CoV-2. Molecular docking studies were performed on holoRdRp and nsp13, two key factors responsible for virus replication factor. Our in silico studies, K-252-C aglycone indolocarbazole alkaloid (K252C) and daunorubicin were found to have better binding affinities than the respective control drugs, with K252C exhibiting binding energy of - 9.1 kcal/mol with holoRdRp and - 9.2 kcal/mol with nsp13, and daunorubicin showing binding energy at - 8.1 kcal/mol with holoRdRp and - 9.3 kcal/mol with nsp13. ADMET analysis, MD simulation, and MM/GBSA studies indicated that K252C and daunorubicin have the potential to be developed as targeted drugs against SARS-CoV-2. The study concludes that K252C and daunorubicin are potential lead compounds that might suppress the inhibition of SARS-CoV-2 replication among the tested microbial compounds and could be developed as targeted drugs against COVID-19. In the future, further in vitro studies are required to validate these findings.

In-silico and in-vitro evaluation of antifungal bioactive compounds from Streptomyces sp. strain 130 against Aspergillus flavus.

Streptomyces spp. are considered excellent reservoirs of natural bioactive compounds. The study evaluated the bioactive potential of secondary metabolites from Streptomyces sp. strain 130 through PKS-I and NRPS gene-clusters screening. GC-MS analysis was done for metabolic profiling of bioactive compounds from strain 130 in the next set of experiments. Identified antifungal compounds underwent ADMET analyses to screen their toxicity. All compounds' molecular docking was done with the structural gene products of the aflatoxin biosynthetic pathway of Aspergillus flavus. MD simulations were utilized to evaluate the stability of protein-ligand complexes under physiological conditions. Based on the in-silico studies, compound 2,4-di-tert butyl-phenol (DTBP) was selected for in-vitro studies against Aspergillus flavus. Simultaneously, bioactive compounds were extracted from strain 130 in two different solvents (ethyl-acetate and methanol) and used for similar assays. The MIC value of DTBP was found to be 314 µg/mL, whereas in ethyl-acetate extract and methanol-extract, it was 250 and 350 µg/mL, respectively. A mycelium growth assay was done to analyze the effect of compounds/extracts on the mycelium formation of Aspergillus flavus. In agar diffusion assay, zone of inhibitions in DTBP, ethyl-acetate extract, and methanol extract were observed with diameters of 11.3, 13.3, and 7.6 mm, respectively. In the growth curve assay, treated samples have delayed the growth of fungi, which signified that the compounds have a fungistatic nature. Spot assay has determined the fungal sensitivity to a sub-minimum inhibitory concentration of antifungal compounds. The study's results suggested that DTBP can be exploited for antifungal-drug development.Communicated by Ramaswamy H. Sarma.

Monoterpenes as potential antifungal molecules against Candida cell membranes: in-vitro and in-silico studies.

Azoles are the frequently used antifungal drugs that target the enzyme lanosterol 14 α-demethylase (erg11p). This enzyme plays a vital role in ergosterol biosynthesis and hence maintainenance of cell membrane fluidity and integrity. The emergence of resistance to azoles and their fungistatic nature against several fungal pathogens is the major challenge to combat invasive candidiasis. Therefore, there is an urgent need to discover new antifungals with better efficacy. This study targets erg11 protein using in silico approach and identifies the monoterpene compounds (α-terpineol, carveol, and terpinene-4-ol) based on docking score and ligand interaction analysis. Further dynamic behavior of best-docked compounds with erg11p was analyzed by various parameters of MD simulation. The binding free energy of selected compounds towards the definitive pocket was also calculated. To further investigate the antifungal activity of selected compounds, in vitro studies were conducted on C. albicans. Studies thus suggest that the proposed the mechanism of antifungal action of test compounds involves targeting the ergosterol biosynthetic pathway. The compounds were explored for their effect on the disruption of membrane integrity by studying ERG11gene expression analysis, scanning electron microscopy, PI uptake (fluorescence microscopy,) and H+-extrusion. The results suggest that the selected monoterpenes are safer natural antifungals that disrupt membrane integrity by inhibiting ergosterol biosynthesis and other membrane associated structures.Communicated by Ramaswamy H. Sarma.

Diosmin in combination with naringenin enhances apoptosis in colon cancer cells.

Colon cancer is one of the most commonly diagnosed malignancies, which begins as a polyp and grows to become cancer. Diosmin (DS) and naringenin (NR) are naturally occurring flavonoids that exhibit various pharmacological activities. Although several studies have illustrated the effectiveness of these flavonoids as anti­cancerous agents individually, the combinatorial impact of these compounds has not been explored. In the present study, the combined effect of DS and NR (DiNar) in colon cancer cell lines HCT116 and SW480 were assessed by targeting apoptosis and inflammatory pathways. The MTT assay was used to evaluate the effect of DiNar on cell proliferation, while Chou­Talalay analysis was employed to determine the combination index of DS and NR. Moreover, flow cytometry was used to monitor cell cycle arrest and population study. The onset of apoptosis was assessed by DAPI staining, DNA fragmentation, and Annexin V­fluorescein isothiocyanate/propidium iodide (Annexin V­FITC/PI). The expression levels of apoptotic pathway markers, Bcl­2, Bax, caspase3, caspase8, caspase9 and p53, and inflammatory markers, NF­κß, IKK­α and IKK­ß, were assessed using western blotting and reverse transcription­quantitative PCR. These results suggested that DiNar treatment acts synergistically and induces cytotoxicity with a concomitant increase in chromatin condensation, DNA fragmentation and cell cycle arrest in the G0/G1 phase. Annexin V­FITC/PI apoptosis assay also showed increased number of cells undergoing apoptosis in the DiNar treatment group. Furthermore, the expression of apoptosis and inflammatory markers was also more effectively regulated under the DiNar treatment. Thereby, these findings demonstrated that DiNar treatment could be a potential novel chemotherapeutic alternative in colon cancer.

Phytochemical based nanomedicines against cancer: current status and future prospects.

Cancer continues to be one in all the leading reasons for death worldwide. The mean cancer survival through standard therapeutic strategies has not been significantly improved over the past few decades. Hence, alternate remedies are needed to treat this terrible disease. Recently, natural compounds present in the plants, i.e. phytochemicals have been widely exploited for their anticancer potential. Phytochemicals may exhibit their anticancer activity through targeting different cancer cell signalling pathways, promoting cell cycle arrest and apoptosis, regulating antioxidant status and detoxification. Despite their excellent anticancer activity, the phytochemicals are limited by their low aqueous solubility, poor bioavailability, and poor penetration into cells, hepatic disposition, narrow therapeutic index and rapid uptake by normal tissues. Therefore, to address these challenges, the scientific community has shifted its significant interests towards nanocarriers-based delivery of phytochemicals due to their ability to enhance aqueous solubility, and bioavailability, specific tumour cell/tissue targeting, improved cellular uptake, reducing doses of phytochemicals and achieving steady-state therapeutic levels of the phytochemicals over an extended period of time. Additional advantages include excellent blood stability, multifunctional design of nanocarriers and improvement in anticancer activities. This review aims to summarise recent progress in phytochemical based nanomedicines for effective treatment of cancer.