In Vitro and In Silico Studies for the Identification of Potent Metabolites of Some High-Altitude Medicinal Plants from Nepal Inhibiting SARS-CoV-2 Spike Protein.

Despite ongoing vaccination programs against COVID-19 around the world, cases of infection are still rising with new variants. This infers that an effective antiviral drug against COVID-19 is crucial along with vaccinations to decrease cases. A potential target of such antivirals could be the membrane components of the causative pathogen, SARS-CoV-2, for instance spike (S) protein. In our research, we have deployed in vitro screening of crude extracts of seven ethnomedicinal plants against the spike receptor-binding domain (S1-RBD) of SARS-CoV-2 using an enzyme-linked immunosorbent assay (ELISA). Following encouraging in vitro results for Tinospora cordifolia, in silico studies were conducted for the 14 reported antiviral secondary metabolites isolated from T. cordifolia-a species widely cultivated and used as an antiviral drug in the Himalayan country of Nepal-using Genetic Optimization for Ligand Docking (GOLD), Molecular Operating Environment (MOE), and BIOVIA Discovery Studio. The molecular docking and binding energy study revealed that cordifolioside-A had a higher binding affinity and was the most effective in binding to the competitive site of the spike protein. Molecular dynamics (MD) simulation studies using GROMACS 5.4.1 further assayed the interaction between the potent compound and binding sites of the spike protein. It revealed that cordifolioside-A demonstrated better binding affinity and stability, and resulted in a conformational change in S1-RBD, hence hindering the activities of the protein. In addition, ADMET analysis of the secondary metabolites from T. cordifolia revealed promising pharmacokinetic properties. Our study thus recommends that certain secondary metabolites of T. cordifolia are possible medicinal candidates against SARS-CoV-2.

Tinospora cordifolia (Willd.) Miers: phytochemical composition, cytotoxicity, proximate analysis and their biological activities.

The present research work has been performed to evaluate the phenolic content, flavonoids content, and cytotoxicity of a multidimensional medicinal plant; Tinospora cordifolia and as well as to determine nutritive value by proximate analysis. The total phenolic and flavonoids contents of Tinospora cordifolia were found to be significantly greater in methanol extract as compared to corresponding hexane extract. Brine shrimp bioassay indicated Tinospora cordifolia is pharmacologically active. The percentage composition of different nutrition parameters namely moisture, total ash, crude fat, protein, fibre, carbohydrate, and vitamin C were assessed. The nutritive values of fresh and dried stem samples were evaluated as 156.44 Kcal/100g and 232.61 Kcal/100g respectively. From Gas column mass spectrometry analysis, it can be reported that inositol, 1-deoxy-, trans-sinapyl alcohol, n-hexadecanoic acid were present in the major amount in methanol stem extract. The findings from this study reveal Tinospora cordifolia contains an adequate amount of phenolic and flavonoids content, vital bioactive antioxidant compounds, and a good source of carbohydrates and fibers which potentially adds to the overall value of the plant.

Vitex negundo Linn.: phytochemical composition, nutritional analysis, and antioxidant and antimicrobial activity.

Vitex negundo (VN) is a widely used plant in folk medicine, namely for the treatment of jaundice, wounds, body ache, toothache, asthma, eye pain, and migraine. These effects have been increasingly attributed to its chemical composition. Here, we assessed the VN chemical and nutritional composition and biological activity, with particular emphasis on antioxidant and antimicrobial effects. VN methanol and hexane extracts revealed the presence of important phytochemical, such as terpenoids, polyphenol, steroids, saponins, phenolic compound and flavonoids. Total phenolic content of VN methanol extract from bark was 1082.473 mg/g GAE and that of leaves was 1382.984 mg/g GAE. The total flavonoids content in VN methanol extract from VN bark was 127.744 mg/g QE and that of leaves was 123.776 mg/g QE. VN methanol extract from bark exhibited high antioxidant effects (IC50=38.47 ppm). The content (%) of ash, moisture, crude fiber, crude protein and fat in VN leaves was, respectively, 7.86%, 18.35%, 6.52%, 9.687% and 6.19%. VN leaves methanol extract revealed antimicrobial activity against Bacillus subtilis and Staphylococcus aureus, with inhibition halos being, respectively, 13 mm and 14 mm, and the MBC values were found to be 1.562 mg/mL and 6.25 mg/mL, respectively. Similarly, VN bark methanol extract led to inhibition halos of 18 mm and 15 mm for B. subtilis and S. aureus, respectively, and the MBC values were found to be 2.372 mg/mL and 0.245 mg/mL. GC-MS analysis of the VN bark methanol extract revealed that monoolein was the major compounds, with an area of 0.57%. Thus, our results encourage the potential use of VN as a medicinal product, with high protein contents, and prominent antioxidant and anti-bacterial effects.

Use of Partial Host Resistance in the Management of Bacterial Blight of Rice.

The progress of bacterial blight epidemics, caused by Xanthomonas oryzae pv. oryzae, varies with environment. The irrigated lowland rice production environment in central Terai (plain) is less conducive to the disease than the irrigated lowland rice production environment in eastern Terai in Nepal. The effect of partial resistance on bacterial blight was studied in central Terai during the wet seasons of 1994, 1995, and 1996. Three partially resistant rice cultivars, Sabitri, Laxmi, and IR54 (possessing the Xa4 gene), and susceptible check IR24 were included in this study. Analysis of pooled data from the 3 years of experiments indicated that rice cultivars differed in resistance based on three epidemiological parameters: disease severity (DS), area under the disease progress curve (AUDPC), and rate of disease increase (r). Estimates of DS, AUDPC, and r were reduced and yield loss was negligible in the partially resistant cultivar Laxmi compared with the susceptible check IR24. IR54, which has partial resistance to X. oryzae pv. oryzae, also showed low DS, AUDPC, and r, which prevented yield loss due to bacterial blight. The locally adapted cultivar Sabitri showed intermediate estimates of DS, AUDPC, r, and yield loss. Earlier and more severe disease developed in the susceptible check IR24, resulting in a yield loss of 22%. Yield losses were mainly due to reductions in number of tillers, number of grains per panicle, and 1,000-grain weight. These data indicate that the use of rice cultivars with high levels of partial resistance will be an effective tool for the management of bacterial blight in central Terai and similar environments in Nepal.

Virulence of Xanthomonas oryzae pv. oryzae on Rice Lines Containing Single Resistance Genes and Gene Combinations.

Fifty isolates of Xanthomonas oryzae pv. oryzae were collected from different rice-producing districts of Nepal and evaluated for their virulence on these 11 rice lines having from one to four resistance genes: IRBB4 (Xa4), IRBB5 (xa5), IRBB7 (Xa7), IRBB8 (xa8), IRBB10 (Xa10), IRBB14 (Xa14), and IRBB21 (Xa21), two-gene combination AY4+5 (Xa4 and xa5), three-gene combinations NH21-37-1-1 (Xa4, xa5, and xa13) and NH24-10-1-3 (Xa4, xa5, and Xa21), and four-gene combination NH56-1-44-4 (Xa4, xa5, xa13, and Xa21). The ability of an isolate to cause lesions with different lengths across the lines was interpreted as virulence. Isolates that were consistently associated with high or low virulence were statistically differentiated. Most isolates produced large lesions on near-isogenic lines with single genes and small lesions on lines with different gene combinations. Based on infection responses on the two-, three-, and four-gene combinations, five virulence groups were identified. Isolates in virulence group I were widely distributed. The line × isolate interactions were generally not significant with gene combinations, indicating a low possibility of specificity. A line with a four-gene combination, NH56, showed wider spectrum and higher level of resistance to X. oryzae pv. oryzae than the other lines. The results of this study will facilitate the deployment of effective resistance to X. oryzae pv. oryzae in Nepal.