Investigation of the immunomodulatory influence of the flavonoid rich fraction of Azadirachta indica in Plasmodium berghei infected mice.

ETHNOPHARMACOLOGICAL RELEVANCE: In Nigeria and other tropical and sub-tropical regions, Azadirachta indica, or neem, is a typical medicinal plant. In traditional medicine, its stem and leaves have been used to treat malaria. AIM OF THE STUDY: Through tryptophan catabolism and the likely mechanisms involved, we aim to examine the immunomodulatory potentials of flavonoid-rich fractions of A. indica extracts by regulating the splenic indoleamine 2, 3-dioxygenase (IDO), a crucial immune system regulator. This is to enunciate scientific proof and information about its therapeutic qualities for the treatment of malaria. MATERIALS AND METHODS: Thirty-six mice weighing between 18 and 23 grams were split into six groups at random, with six mice in each group. When parasitemia was clearly visible in the infected mice on day four, treatment of the mice in experimental groups B through F began. RESULTS: HPLC analysis showed the presence of naringenin, apigenin, kaemferol, luteolin, rutin, and quercetin. The various flavonoids identified in the FRF-Ai in the current study further highlighted its richness in flavonoid compounds. There was a time dependent increase in percentage parasitemia in the infected/untreated group, whereas, treatment with artesunate brought the level of the parasite to zero while treatment with FRF-Ai elicited a significant reduction in the level of the parasite and an attendant increase in the percentage inhibition of the parasite in a dose and time dependent manner. The integrated computational analyses revealed that rutin and naringenin elicited highest inhibition activity on indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) by occupying and stabilizing the enzymes' active sites. P. berghei infection resulted in the inhibition of antioxidant status and the elevation of lipid peroxidation and pro-inflammatory cytokine IL-6, MPO activity, and levels of NO in the splenocyte of the infected mice. Additionally, elevation in the serum kynurenine concentrations and activities of immunosuppressive IDO and TDO in the splenocytes of mice infected with P. berghei was convoyed by decrease in WBC, RBC, and CD4+ T cells, compared to the control group. However, the treatment with FRF-Ai exhibited a significant (p < 0.05) reversal in the altered parameters of immune response relative to the control group thereby counteracting immunosuppression. FRF-Ai could substantially control immune responses in malaria infection through the antioxidant, anti-inflammatory activities, by regulating Trp catabolism via IDO and TDO activity and hematological indices, ultimately leading to enhanced CD4+ T cell.