Antimycobacterial and Nitric Oxide Production Inhibitory Activities of Triterpenes and Alkaloids from Psychotria nuda (Cham. & Schltdl.) Wawra

Abstract

A phytochemical study of leaves and twigs of <i>Psychotria nuda</i> resulted in 19 compounds, including five indole alkaloids, <i>N</i>,<i>N</i>,<i>N</i>-trimethyltryptamine, lyaloside, strictosamide, strictosidine, and 5α-carboxystrictosidine; two flavonolignans, cinchonain Ia and cinchonain Ib; an iridoid, roseoside; a sugar, lawsofructose; a coumarin, scopoletin; a diterpene, phytol; three triterpenes, pomolic acid, spinosic acid, and rotungenic acid; and five steroids, sitosterol, stigmasterol, campesterol, <i>β</i>-sitosterol-3-<i>O</i>-<i>β</i>-d-glucoside, and <i>β</i>-stigmasterol-3-<i>O</i>-<i>β</i>-d-glucoside. Some compounds were evaluated for their in vitro activity against <i>Mycobacterium tuberculosis</i> and their ability to inhibit NO production by macrophages stimulated by lipopolysaccharide (LPS). The compounds pomolic acid, spinosic acid, strictosidine, and 5α-carboxystrictosidine displayed antimycobacterial activity with minimum inhibitory concentrations ranging from 7.1 to 19.2 µg/mL. These compounds showed promising inhibitory activity against NO production (IC₅₀ 3.22 to 25.5 μg/mL). <i>5</i>α-carboxystrictosidine did not show cytotoxicity against macrophages RAW264.7 up to a concentration of 100 µg/mL. With the exception of strictosamide, this is the first report of the occurrence of these substances in <i>P. nuda</i>.