Chapter 6 The Carbazole Alkaloids

Abstract

This chapter presents information on carbazole alkaloids. Carbazole alkaloids represent a new and interesting variant in the large number of existing indole alkaloids that, in the past, have yielded several important drugs. There has been considerable progress in this field; currently, about 19 alkaloids, from simple compounds like 6-methoxy-3-methylcarbazolteo complex hexacyclic bases, are known. In most cases, their structures have been elucidated by the application of modern physical methods and confirmed by syntheses. This chapter discusses those members of this series having an extra carbon unit at C-3 or C-6. A rich and rewarding source of carbazole alkaloids has been the Indian curry leaf plant Murraya koenigii Spreng (Rutaceae). The roots of Glycosmis pentaphylla (Retz.) and Clausena heptaphylla have also yielded new carbazole alkaloids. The crucial information that murrayanine is a carbazole derivative was provided by zinc dust distillation-carbazole was obtained. Similarly, the Wolff–Kishner reduction product of murrayanine on zinc dust distillation yielded 3-methylcarbazole. The chapter also discusses C13-alkaloids, C18-alkaloids, C23-alkaloids, and others. The crude extract of M. koenigii has shown activity against Entamoeba histolytica, while girinimbine is reported to be active against Nocardia asteroides fungi.