Two novel monoterpenoid indole alkaloids, aspidochibine (1) and 3-0x0-14,15-dehydrorhazinilam (2), were isolated from cell suspension cultures of Aspidosperma quebrucho blunco Schlecht. Aspidochibine (1) exhibits a new alkaloid skeleton. The structure of these alkaloids was elucidated by spectroscopic methods.
The medicinal plant Aspidosperrna quebrucho blunco Schlecht is endemic to South America and is therapeutically used in e. g. the treatment of bronchial asthma and dyspnoe. The bark of this tree contains more than 30 monoterpenoid indole alkaloids. Because some of these Quebrucho-alkaloids are structurally and biogenetically strongly related to alkaloids of the ajmalan type we initiated callus and cell suspension cultures from hypocotylic sections of 2 weeks old seedlings to investigate the alkaloid profile in the culture systems.
Whereas callus formation on agar plates supplemented with LS-or 4X-medium1-3 occurred already within 6-7 weeks, efficiently growing cell suspensions could be established only after about 20 subcultivations (-1 year). In average this culture produced 130 g fresh material (10.4 g dry weight) per 1 medium within 14 days.
From these cell suspensions three nitrogenous metabolites could be isolated in trace amounts. They were two novel indole alkaloids, AQC-2 (1) and AQC-3 (2), named aspidochibine and 3-oxo-14,15-dehydrorhazinilam respectively, and a new dioxopiperazine. In this paper studies on the structures of both indole alkaloids are described.
Aspidochibine (AQC-2)(1),4 ClgH22N20 2, is an alkaloid of a new structural class of the