Uncovering the inhibitory potentials of Phyllanthus nivosus leaf and its bioactive compounds against Plasmodium lactate dehydrogenase for malaria therapy

Malaria control efforts have been hampered due to the emergence of resistant malaria parasite strains and the coinciding events of Covid-19. The quest for more effective and safe treatment alternatives is driving a slew of new studies that must be accelerated if malaria can be overcome. Due to its reported antimalarial activity, we studied the effects of extract and fractions of Phyllanthus nivosus leaf on Plasmodium lactate dehydrogenase (pLDH) activity using an in vitro assay. This was followed by an anti-plasmodial study using Plasmodium berghei-infected mice and an in silico identification of the plant's phytochemicals with possible pLDH-inhibitory activity. The activity of pLDH was significantly reduced in the presence of ethanol extract and various solvent fractions of Phyllanthus nivosus leaf, with the ethyl acetate fraction having the best inhibitory activity, which was comparable to that of the standard drug (chloroquine). The ethyl acetate fraction at 100 and 200 mg/Kg also suppressed the parasitaemia of Plasmodium berghei-infected mice by 76 and 80% respectively. Among the 53 compounds docked against pLDH, (-)-alpha-Cadinol, (+)-alpha-phellandrene, and spathulenol, all terpenes from the ethyl acetate fraction of P. nivosus leaf extract, demonstrated docking scores comparable to that of chloroquine. The three chemicals, like chloroquine, displayed important molecular interactions with the amino acid residues of the enzyme's NADH-binding site. According to the in silico ADMET study, the three terpenes have suitable drug-like abilities, pharmacokinetic features, and safety profiles. Hence, they could be considered for further development as antimalarial drugs.Communicated by Ramaswamy H. Sarma.