Lignans from Stem Bark of Zanthoxylum rigidum (Rutaceae) and their Leishmanicidal Activities

ABSTRACT: 

The genus Zanthoxylum (Rutaceae), comprising approximately 250 species, is well-known for its several ethnobotanical uses. The plants belonging to this genus are sources of biologically active compounds, such as alkaloids, aliphatic and aromatic amides, coumarins, lignans and cyclopeptides. Many pharmacological activities such as antiplasmodic, anti-HIV, anti-inflammatory, antihelmintic, gastroprotective and cytotoxic properties for Zanthoxylum species have been reported. Zanthoxylum rigidum is known popularly in Brazil as mamica-de-porca “pig’s nipple” or mamica-de-cadela “dog’s nipple” due to the particular shape of its thorn.  In this research were isolated three known lignans sesamin, dimethylmatairesinol and methylpluviatolide, and other compounds as lupeol, a mixture of the steroids stigmasterol, b-sitosterol and campesterol, quercetin, and D-mannitol from stem bark of the Zanthoxylum rigidum. These compounds had its structures elucidated with the help of nuclear magnetic resonance spectroscopy one-dimensional (¹H, ¹³C and DEPT-Q) and two-dimensional (COSY, HMQC and HMBC) and mass spectrometry (EIMS). The lignans isolated were tested for their ability to inhibit the proliferation of the promastigote forms of Leishmania braziliensis and Leishmania chagasi. The best results were obtained with sesamin and methylpluviatolide that showed IC₅₀ = 22.43 and 33.60, SI = 3.87 and 2.41 and CC₅₀ = 86.9 and 81.2, for L. braziliensis and L. chagasi, respectively. This study is a part of an ongoing research program to discover bioactive compounds in the Brazilian flora.