Sub-acute toxicity studies and dynamics-based molecular insights on the in vivo antimalarial activity of Ilex umbellulata (Wall.) Loes bark in Plasmodium berghei-infected mice.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: The tribals of Mizoram, Northeast India, use Ilex umbellulata to treat malaria, tonsillitis, dysentery, and inflammation. Other tribes in Southeast Asia, such as those in Meghalaya, India, use the bark to treat indigestion, while in Thailand, the fruit is used to treat stomach aches. AIM OF THE STUDY: This study assessed the sub-acute oral toxicity and evaluated the in vivo antimalarial activity of I. umbellulata in a mouse model of Plasmodium berghei-induced malaria. The study also identified, through computational studies, the molecular mechanism underlying the observed in vivo antimalarial activity. MATERIAL AND METHODS: I. umbellulata bark was collected from Mizoram, and authentication was done at the Botanical Survey of India. Maceration was carried out to obtain an 80 % methanol (MeOH) extract. With proper ethical clearance, Organization for Economic Cooperation and Development (OECD) guidelines 425 and 407 were followed to carry out acute toxicity and sub-acute toxicity studies, respectively. Evaluation of the in vivo antimalarial activity was done using Peter's 4-day suppressive test. The mechanistic insights of the phytocompounds of I. umbellulata were investigated using in silico approaches. RESULTS: The lethal dose 50 % (LD) of the 80 % MeOH bark extract of I. umbellulata was above 2000 mg/kg b.w., and it was safe for oral consumption in mice for up to 28 days. Treatment of the mice with a 200 mg/kg dose resulted in the lowest parasitaemia (5.00 ± 0.97 %), the highest parasite suppression (85.65 ± 2.77 %), and the longest number of days survived post-infection (15.33 ± 2.82 days). Molecular docking simulation studies, molecular dynamic (MD) simulations, and molecular mechanics-generalized born surface area (MM-GBSA) calculations revealed that the ability of Cyanidin-3-O-rutinoside to interact with the active site residues of enoyl-acyl-carrier-protein reductase (PbEACPR), thereby inhibiting fatty acid biosynthesis, may be one of the reasons for the observed in vivo antimalarial activity of the 80 % MeOH bark extract. CONCLUSION: The study establishes I. umbellulata as a promising antimalarial candidate with the potential for global application. The findings of the study encourage the development of antimalarial herbal formulations.