Inhibition of Heme Polymerization, the Mechanism of Antimalarial Activity in Phlomis caucasica Rech.f. (Lamiaceae)

Background: Malaria is one of the most important parasitic diseases in the world caused by Plasmodium species. The malaria parasite digests hemoglobin in vacuole to amino acids and heme. Plasmodium has got several detoxification mechanisms to protect itself from toxic heme. The most important mechanism is heme polymerization. Identifying compounds that inhibit heme polymerization is an approach for detecting antimalarial drugs. Objective: This work has intended to screen some plants from Lamiaceae family for mechanism of antimalarial by ITHD (Inhibition Test of Heme Detoxification). Method: Inhibition of heme polymerization of total methanol extracts from seven plants of Lamiaceae family have been evaluated by the ITHD method. Hemin Chloride, tween 20 and samples were added in each well of a 96-well plate with ratio 9:9:2, and incubated at 60ºC for 24 h. The plate was read with a micro-ELISA reader at 405 nm, and percentage of heme polymerization inhibition was calculated. The fractions including petroleum ether, chloroform, methanol, methanol: water (7:3) and water were obtained by maceration and the inhibition of heme polymerization evaluation were assessed using the ITHD. Results: Total methanol extracts of Marrubium astracanicum Jacq. and Phlomis caucasica Rech.f. demonstrated inhibition of heme polymerization, 40 and 35% respectively. The aqueous fraction of P. caucasica inhibited heme polymerization 100%. Conclusion: P. caucasica could be a selective candidate for drug discovery program in malaria.