Fascinating organic molecules from nature

Abstract

From the very beginning of civilization, humans have used chemicals from Nature — most of them comparatively small organic molecules now designated as secondary metabolites — for a variety of purposes such as pigments and dyes, arrow and fish poisons and olfactory stimulants.

It is no wonder that many eminent chemists were attracted to these materials to elucidate the underlying chemistry. Willstatter, Baeyer, Richard Kuhn, Karrer, Robinson and others made pioneering studies and isolated several new compounds which were included in the curriculum of earlier days. Another pioneer, A G Perkin, second son of Sir W H Perkin, was, according to his elder brother, W H Perkin, Jr, a dabhand with natural dyes.He andAE Everest wrote a book The Natural Organic Colouring Matters, first published in 1918, which was like a Bible to natural product chemists of yesteryears. (You can now read it on line!).

As organic chemistry progressed, making leaps and bounds, the newer exciting discoveries gradually pushed the study of several of these compounds out of the curriculum. While one can understand this trend, one also feels sad that students these days are not aware of several interesting facets of natural products chemistry which link organic chemistry with folklore, traditional practices by diverse native communities, indigenous systems of medicine and current ideas of chemical structure and reactivities. It is not possible to fill in these gaps in textbooks which are designed to cater to the needs of students preparing for various university examinations, but articles such as those contemplated here can provide students with knowledge that can be stimulating, interesting as well as enjoyable!

We begin the series with ’some exotic red pigments of plant origin’. Several red coloured dyes and pigments of vegetable origin have been known to mankind ever since the dawn of civilization. Their varied uses have been mentioned in ancient literature, including the Ramayana, folklores, travelogues and accounts of several explorers. Their chemistry is equally fascinating and has attracted the attention of a number of eminent organic chemists. In this article, we examine a few of these pigments isolated from plant materials found in different parts of the world. They include the pigments of the red sandalwood, the colourants of safflower, the exotic cosmetic chica red, brazilin from the Brazil wood (and the related hematoxylin), the compounds from the Dragon’s blood, the sesquiterpene quinones of the Miro wood and rottlerin, the main red pigment of Kamala dye.