Anti-plasmodial activity and immuno-modulatory properties of extracts of Picralima nitida fruit-rind and leaves in Plasmodium berghei-infected mice

Abstract

Malaria, an infectious disease caused by Plasmodium parasites, remains a significant public health concern, particularly in tropical and subtropical regions. While global efforts between 2005 and 2015 led to a notable decline in malaria-related mortality and morbidity, the emergence of Plasmodium falciparum resistance to artemisinin-based combination therapy (ACT) in regions such as South-East Asia has raised alarm. This resistance poses a heightened threat to malaria control, especially in low-income countries like Nigeria, where access to alternative treatments is limited. As part of strategies to address drug resistance, research has intensified into discovering new antimalarial agents from medicinal plants. One such plant is Picralima nitida, from the Apocynaceae family, traditionally used in southern Nigeria to treat malaria. This study evaluated the antiplasmodial and immunomodulatory effects of dichloromethane-methanol (1:1) extracts of P. nitida fruit rind and leaves in mice infected with Plasmodium berghei. Extracts were prepared using a solvent mixture of dichloromethane and methanol and tested using the four-day suppressive test in Swiss mice. Phytochemical analysis showed the leaf extract contained more bioactive compounds than the fruit rind. The extracts demonstrated significant (p<0.05) dose-dependent antiplasmodial activity compared to the untreated control group. Additionally, treated mice exhibited reduced oxidative stress markers and lower levels of pro-inflammatory cytokines, indicating immunomodulatory effects. These results suggest that P. nitida extracts possess both antiplasmodial and immune-modulating properties, supporting its traditional use and potential for further development as a plant-based malaria therapy, particularly in areas affected by artemisinin resistance.