Malaria is an infectious disease caused by Plasmodium parasites. Approximately 3.3 billion people (half of the world’s population) are at risk of malaria. According to the latest reports of WHO, there has been roughly 212 million malaria cases and an estimated 429000 malaria deaths in 2015. The malaria parasite digests hemoglobin in vacuole into amino acids and heme. Free heme is toxic for the parasite and Plasmodium has got several detoxification mechanisms such as hemozoin formation, heme-binding proteinsand degradation of free heme by H2O2 to protect itself from toxic heme. Some drugs show anti-malarial effects via inhibition of hemozoin formation which is the most important mechanism for detoxification. β-hematin, which is identical to hemozoin, is a synthetic polymer that is used for malaria in vitro assessments. Identifying compounds that inhibit β-hematin formation is an approach for detecting new anti-malarial agents.
There are several methods to assess the in vitro capability of heme inhibitory activity of antimalarial compounds; most of them require some specific equipment or toxic substances and sometimes the needed materials are not accessible. Regarding the necessity and importance of optimizing and standardizing experimental conditions, the present study has done with the in vitro assessment conditions of the β-hematin formation inhibitory activity for screening herbal samples.
Hemin, tween 20, and samples (9:9:2) were incubated in blow condition, including: hemin concentration (60 μg/mL), duration (24 h), pH of buffer (4.8), and temperature (60 °C) in 96-well plates. Also, a total of seven methanol plant extracts were tested in the most suitable conditions. The reaction time and the incubation temperature were determined as the critical factors. In this method, proper correlations with respect to negative (69%) and positive (67%) predictive values were obtained in comparison with the anti-plasmodial assay.
The results of anti-malarial activities of Cousinia harazensis, Co. calocephala, Co. peterocaules, Cirsium lappaceum, Chenopodium album, Bassia stricta and Wild Medicago sativa are as follows: 23, 45, 51, 12, 22, 36 and 34%.
None of these seven plants there are not placed in the range and they cannot consider as new anti-malarial agents.