Indole Alkaloids from <i>Geissospermum reticulatum</i>

Ten indole alkaloids were isolated from <i>Geissospermum reticulatum</i>, seven (<b>1</b>–<b>7</b>) from the leaves and three (<b>8</b>–<b>10</b>) from the bark. Seven were aspidospermatan-type alkaloids (<b>1</b>–<b>3</b>, <b>5</b>–<b>9</b>), including four (<b>5</b>–<b>8</b>) with a 1-oxa-3-cyclopentene group in their molecule, which we named geissospermidine subtype. Compounds <b>1</b>–<b>3</b>,<b> 5</b>–<b>8</b>, and <b>10</b> had not been reported previously as natural products, while <b>4</b> and <b>9</b> were the known alkaloids <i>O</i>-demethylaspidospermine and flavopereirine. Their structures were determined by spectroscopic techniques including 1D and 2D NMR experiments (COSY, NOESY, HSQC, HMBC). Additionally, X-ray crystallographic analyses of <b>1</b>, <b>2</b>, and <b>6</b> were performed. Antiparasitic activities of the ethanolic and alkaloidal extracts and of the pure alkaloids were tested against <i>Trypanosoma cruzi</i> and <i>Leishmania infantum.</i> In general, the extracts exhibited selective action and were more active against <i>Leishmania</i> than against <i>Trypanosoma</i>. Alkaloid <b>4</b> was also very active against <i>L. infantum