Abstract

In Burkina Faso and neighbouring countries, a red dye extracted from sorghum is used to colour leather, wickerwork, and gourd. Sorghum is the only plant known to contain significant quantities of desoxy-3-anthocyanins, which are important in the dyeing industry. The first phase of this project established the exceptionally high content of the chemical in the plant and developed an extraction procedure at the laboratory level. This second phase will isolate and characterize minor anthocyanins present in the mixture; build a pilot unit to perfect the process of extracting a superior product; and carry out market studies.

Post-Project Summary

The Ouagadougou team was able to isolate some minor components of dyers' sorghum that both teams subsequently attempted to identify. The Simon Fraser University (SFU) team shipped eight commercially available anthocyanins to Ouagadougou for comparison with the minor components isolated from dyers' sorghum and other sources. Using chromatography and nuclear magnetic resonance spectroscopy, it was established that dyers' sorghum is 95% pure apigenidin chloride. This 3-deoxyanthocyanidin is very stable, whereas the minor components of dyers' sorghum are less stable. The essential background work for successful extraction at the pilot plant stage having been carried out in Phase I (88-1034), SFU researchers visited Ouagadougou in April 1992 to optimize the extraction process at the laboratory scale (1-10 litres) and discuss the design of the plant. The Ouagadougou team had been evaluating options for the purchase of an intermediate scale unit involving a 20-50-l extractor unit and a 20-50-l rotary evaporator/concentrator, but the equipment had not been ordered as of August 1993 when both teams met in Quebec. A larger-scale (100-600-l) installation provided by the Belgian government for natural products extraction was already in place in Ouagadougou. The use of apigenidin chloride in coloring cow salt blocks and sale in local markets for leather coloring was under development by the Ouagadougou team. In order to study the international market for 3-deoxyanthocyanidin, the SFU team sent a letter of enquiry to 64 companies in the business of selling dyes for the food, beverage and pharmaceutical sectors, along with a sample of apigenidin chloride. Responses were directed to the Ouagadougou team. The team set the preliminary price of their 3-deoxyanthocyanidin at US $300/gram, which compared favorably with the retail prices obtained in late 1993 by the SFU team on other dyes in this class. The Ouagadougou team estimated (early 1994) that they could produce 1 000 g of apigenidin chloride in 1994.

Recipient Institution(s)