Antimalarial Anthrone and Chromone from the Leaf Latex of Aloe debrana Chrstian
In Ethiopian traditional medicine, the leaf latex of Aloe debranan Chrstian is used for the treatment of several diseases including malaria. In an ongoing search for effective, safe and cheap antimalarial agents from plants, the leaf latex of A. debrana was tested for its in vivo antimalarial activity, in a 4-day suppressive assay against Plasmodium berghei. Activity-guided fractionation of this latex which showed good antiplasmodial activity resulted in the isolation of two compounds identified as 10-C-β-D-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthracenone, commonly known as aloin, and (E)-2-(1-hydroxy-2-methylpropyl)-8-(6'-O-cinnamoyl)-β-D-glucopyranosyl-7-methoxy-5-methylchromone (HCGMM). Aloin displayed a significant (p<0.05) antimalarial activity at doses of 25, 50 and 100 mg/kg with chemosuppression values of 48.38, 69.66 and 78.31%, respectively, while the effect of HCGMM was slightly less than that of aloin inhibiting growth of the parasite by 35.49, 47.02 and 63.13%, at the same doses. Acute toxicity studies revealed that the latex possesses no toxicity in mice up to a maximum dose of 5000 mg/kg suggesting the relative safety of the plant when administered orally. The results of the present study indicate that aloin and HCGMM are among the antimalarial principles in this medicinal plant, and further support claims for the traditional medicinal use of the plant for the treatment of malaria.
Keywords: leaf latex, Aloe debrana, antimalarial, aloin, (E)-2-(1-hydroxy-2-methylpropyl)-8-(6'-O-cinnamoyl)-β-D-glucopyranosyl-7-methoxy-5-methylchromone