Antiparasitic Constituents of Beilschmiedia louisii and Beilschmiedia obscura and Some Semisynthetic Derivatives (Lauraceae)

Abstract

The MeOH/CH₂Cl₂ (1:1) extracts of the roots and leaves of <i>Beilschmiedia louisii</i> and <i>B. obscura</i> showed potent antitrypanosomal activity during preliminary screening on <i>Trypanosoma brucei brucei</i>. Phytochemical investigation of these extracts led to the isolation of a mixture of two new endiandric acid derivatives beilschmiedol B (<b>1</b>) and beilschmiedol C (<b>2</b>), and one new phenylalkene obscurene A (<b>3</b>) together with twelve known compounds (<b>4</b>-<b>15</b>). In addition, four new derivatives (<b>11a</b>-<b>11d</b>) were synthesized from compound <b>11</b>. Their structures were elucidated based on their NMR and MS data. Compounds <b>5</b>, <b>6</b>, and <b>7</b> were isolated for the first time from the <i>Beilschmiedia</i> genus. Additionally, the NMR data of compound <b>4</b> are given here for the first time. The isolates were evaluated for their antitrypanosomal and antimalarial activities against <i>Tb brucei</i> and the <i>Plasmodium falciparum</i> chloroquine-resistant strain <i>Pf3D7</i> in vitro, respectively. From the tested compounds, the mixture of new compounds <b>1</b> and <b>2</b> exhibited the most potent antitrypanosomal activity in vitro with IC₅₀ value of 4.91 μM.