Leishmanicidal and cytotoxic activity of hederagenin-bistriazolyl derivatives

Abstract Aiming to obtain new potent leishmanicidal and cytotoxic compounds from natural sources, the triterpene hederagenin was converted into several new 1,2,3-triazolyl derivatives tethered at C-23 and C-28. For this work hederagenin was isolated from fruits of Sapindus saponaria and reacted with propargyl bromide to afford as a major product bis-propargylic derivative 1 in 74%. Submitting this compound to Huisgen 1,3-dipolar cycloaddition reactions with several azides afforded the derivatives 2 – 19 with yields in the range of 40–87%. All compounds have been screened for in vitro cytotoxic activity in a panel of five human cancer cell lines by a SRB assay. The bioassays showed that compound 19 was the most cytotoxic against all human cancer cell lines with EC 50  = 7.4–12.1 μM. Moreover, leishmanicidal activity was evaluated through the in vitro effect in the growth of Leishmania infantum , and derivatives 1 , 2 , 5 and 17 were highly effective preventing proliferation of intracellular amastigote forms of L. infantum (IC 50  = 28.8, 25.9, 5.6 and 7.4 μM, respectively). All these compounds showed a higher selectivity index and low toxicity against two strains of kidney BGM and liver HepG2 cells. Compound 5 has higher selectivity (1780 times) in comparison with the commercial antimony drug and is around 8 times more selective than the most active compound previously reported hederagenin derivative. Such high activity associated with low toxicities make the new bis-traiazolyl derivatives promising candidates for the treatment of leishmaniasis. In addition, hederagenin and some derivatives ( 2 , 5 and 17 ) showed interaction in the binding site of the enzyme CYP51 Li .