ORIGINAL PAPER In vitro and in vivo activity of Aloe vera leaf exudate in experimental visceral leishmaniasis Avijit Dutta & Debjani Sarkar & Ameenah Gurib-Fakim & Chitra Mandal & Mitali Chatterjee Received: 9 January 2008 / Accepted: 21 January 2008 # Springer-Verlag 2008 Abstract The leishmanicidal activity of Aloe vera leaf exudate (AVL) has been demonstrated in promastigotes and axenic amastigotes, but its effectiveness in animal models has not been evaluated. The presence of alkaloids, triterpenes, cyanidines, proanthocyanidines, tannins, and saponins in AVL was identified. Its effectiveness in four Leishmania donovani strains was studied both in promas- tigotes (IC 50 ranged from 70–115 μg/ml) and amastigotes (IC 50 ranged from 3.1–11.4 μg/ml). In amastigotes, the killing by AVL was facilitated through its induction of nitric oxide in leishmania-infected macrophages. The safety index was good as AVL up to 300 μg/ml remained non- toxic to monocytes and macrophages. In a L. donovani BALB/c mouse model, oral or subcutaneous administration of AVL (15 mg/kg body weight×5 days) reduced para- sitemia by >90% in the liver, spleen, and bone marrow without impairment of hepatic and renal functions. Collec- tively, we conclude that AVL shows promising antileish- manial activity and may provide a new lead agent in the treatment of Leishmaniasis. Introduction Leishmaniasis is a vector-borne complex parasitic disease caused by obligate intra-macrophage protozoan parasite Leishmania and threatens almost 350 million people worldwide with about two million new cases reported each year. It is manifested in visceral, mucocutaneous, or cutaneous forms, severest being the visceral form (VL) with an estimated 500,000 new cases annually (Desjeux 2004). Progress in developing a protective vaccine against leishmaniasis has to date not been effective. The Indian subcontinent, a major endemic area of VL, is currently facing an unprecedented increase in primary unresponsive- ness to sodium antimony gluconate (SAG), the first line of treatment (Chappuis et al. 2007). The chemotherapy of VL includes Amphotericin B and its lipid formulations but its limitations include parenteral administration, toxicity, and high cost (Guerin et al. 2002). Paromomycin, Sitamaquine, and combinational therapies are under the process of evaluation but are not devoid of toxicity (Chappuis et al. 2007). Parasitol Res DOI 10.1007/s00436-008-0899-2 Chitra Mandal and Mitali Chatterjee should be considered as joint senior authors. A. Dutta : C. Mandal Department of Infectious Disease and Immunology, Indian Institute of Chemical Biology, 4 Raja SC Mullick Road, Kolkata 700032, India C. Mandal e-mail: cmandal@iicb.res.in D. Sarkar : M. Chatterjee (*) Department of Pharmacology, Institute of Postgraduate Medical Education and Research, 244 B Acharya JC Bose Road, Kolkata 700 020, India e-mail: ilatim@vsnl.net A. Gurib-Fakim Department of Chemistry, University of Mauritius, Reduit, Mauritius A. Dutta Division of Infectious Disease, Department of Medicine, Chang Gung University School of Medicine and Hospital, 5 Fushing Street, Kweishan, Taoyuan 33333, Taiwan