Antileishmanial Activity of Some Abietane Diterpenoids from Taxodium distichum

As part of ongoing efforts to discover natural product compounds with antileishmanial activity as potential new drug candidates, a series of previously produced plant extracts was screened for toxicity against Leishmania donovani amastigotes and promastigotes, two forms of the organism responsible for the fatal sub-classification of visceral leishmaniasis. Following up on one positive hit, a simple fractionation of the methanolic extractive of an Ohio plant, found on the Ohio State University's (OSU) campus and identified as Taxodium distichum Rich. (Cupressaceae) at the OSU herbarium, has led to the observation of antileishmanial activity against L. donovani promastigotes and amastigotes in vitro. One active fraction was selected for further study and was observed to be effective in vivo as well, reducing the parasitic load at the spleen and liver of the murine model system. Further phytochemical investigation directed by in vitro antileishmanial activity has thus far yielded a series of compounds representative of the C-ring aromatized abietane diterpenoids.