Immunomodulatory effects of epiphytic Loranthus micranthus leaf extracts collected from two host plants: Psidium guajava and Parkia biglobosa.

BACKGROUND: Immunological abnormalities are implicated in the pathogenesis of many chronic diseases. Due to the drug-related adverse effects of currently available orthodox immunomodulators, natural immunomodulators are being looked upon as potential agents to replace them in therapeutic regimens. This research aimed to investigate the immunomodulatory potential of L. micranthus extracts epiphytic on Psidium guajava (LMPGE) and Parkia biglobosa (LMPBE). METHODS: Phytochemical screening and acute toxicity testing were carried out to identify the phytoconstituents and safety profiles of the extracts. The extracts' innate and adaptive immunomodulatory potentials were determined in experimental animals using in vivo leucocyte mobilization, delayed-type hypersensitivity (DTH) response, hemagglutination antibody titre, and cyclophosphamide-induced myelosuppression models. Levamisole was used as the standard drug throughout the study. RESULTS: Compared to LMPBE, LMPGE contained significantly (p <  0.05) more tannins, cyanogenic glycosides, saponins, reducing sugars, glycosides, flavonoids, and alkaloids. Furthermore, the groups treated with the extracts had a significant (p <  0.05) increase in the total number of leucocytes, neutrophils, basophils, and antibody titers relative to the untreated control. In the same way, the treatment raised TLC in cyclophosphamide-intoxicated rats, with 250 mg/kg b. w. of LMPGE and LMPBE recording 9712.50 ± 178.00 and 8000.00 ± 105.00 ×  109 /L, respectively, compared to 3425.00 ± 2 5.00 × 109 /L in the untreated group. Overall, LMPGE was more effective. CONCLUSIONS: The findings from this study suggest that L. micranthus epiphytic in Psidium guajava and Parkia biglobosa has possible immune stimulating potential.

A Computational Approach to Elucidate the Interactions of Chemicals From Artemisia annua Targeted Toward SARS-CoV-2 Main Protease Inhibition for COVID-19 Treatment.

The inhibitory potential of Artemisia annua, a well-known antimalarial herb, against several viruses, including the coronavirus, is increasingly gaining recognition. The plant extract has shown significant activity against both the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and the novel SARS-CoV-2 that is currently ravaging the world. It is therefore necessary to evaluate individual chemicals of the plant for inhibitory potential against SARS-CoV-2 for the purpose of designing drugs for the treatment of COVID-19. In this study, we employed computational techniques comprising molecular docking, binding free energy calculations, pharmacophore modeling, induced-fit docking, molecular dynamics simulation, and ADMET predictions to identify potential inhibitors of the SARS-CoV-2 main protease (Mpro) from 168 bioactive compounds of Artemisia annua. Rhamnocitrin, isokaempferide, kaempferol, quercimeritrin, apigenin, penduletin, isoquercitrin, astragalin, luteolin-7-glucoside, and isorhamnetin were ranked the highest, with docking scores ranging from -7.84 to -7.15 kcal/mol compared with the -6.59 kcal/mol demonstrated by the standard ligand. Rhamnocitrin, Isokaempferide, and kaempferol, like the standard ligand, interacted with important active site amino acid residues like HIS 41, CYS 145, ASN 142, and GLU 166, among others. Rhamnocitrin demonstrated good stability in the active site of the protein as there were no significant conformational changes during the simulation process. These compounds also possess acceptable druglike properties and a good safety profile. Hence, they could be considered for experimental studies and further development of drugs against COVID-19.