Isolation, Characterization and In Vivo Antimalarial Evaluation of Anthrones from the Leaf Latex of Aloe percrassa Todaro

Abstract

Malaria remains a critical problem in global public health and continues to remain among the top three infectious diseases (along with tuberculosis and HIV) due to resistance of the pathogen to antimalarial drugs. Aloe percrassa Tod is an indigenous species of Ethiopia traditionally used for the treatment of malaria, wounds and gastric problems. The present study focused on isolation and characterization of antiplasmodial constituents from the latex of A. percrassa using Peter's 4-day suppressive test. After a four day treatment of Plasmodium berghei infected mice with the latex at doses of 100, 200 and 400 mg/kg/day, chemosuppression of 45.9%, 56.8% and 73.6% was observed, respectively. Further phytochemical examination of the latex by preparative TLC over silica gel resulted in the isolation of two anthrones, viz. aloin A/B and microdontin A/B, whose structures were determined on the basis of UV, MS, ¹H, and ¹³C NMR spectral data. Antimalarial activities of both aloin A/B and microdontin A/B were lower than that of the latex suggesting that the two compounds may have acted synergistically. No adverse sign of toxicity and mortality was observed in mice within the first 24 h as well as for the following 14 days after the test substances were orally administrated up to a dose of 2 g/kg for the pure compounds and 5 g/kg for the latex. The strong antimalarial activities coupled with a relative safety of the leaf latex and isolated compounds of A. percrassa may confirm the claim by traditional practitioners for the use of the plant against malaria infection.