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United States Department of Agriculture

Agricultural Research Service

Title: Separation and Purification of Gossypol, 6-Methoxy-Gossypol and 6,6'-Dimethoxy-Gossypol from Sea Island Gossypium Barbadense

Authors
item Dowd, Michael
item Pelitire, Scott

Submitted to: American Oil Chemists' Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 20, 2005
Publication Date: May 1, 2005
Citation: Dowd, M.K., Pelitire, S.M. 2005. Separation and purification of gossypol, 6-methoxy-gossypol and 6,6'-dimethoxy-gossypol from sea island gossypium barbadense (abstract). Book of Abstracts, 2005 96th American Oil Chemists' Society Meeting, May 1-4, Salt Lake City, UT. p. 98-99.

Technical Abstract: Cotton (Gossypium sp.) is well known to contain gossypol, a polyphenolic yellow pigment gossypol that provides the plant with some fungal and insect resistance, but also limits the use of cottonseed as a feed ingredient. In some G. barbadense varieties, 6-methoxy- and 6,6'-dimethoxy-gossypol derivatives also exist that can account for up to 70% of the total gossypol fraction. In order to test the biological activity of these derivatives, a Sea Island cotton (St. Vincent Superfine) was grown in New Orleans for the past three years. Seed and root bark were harvested from these plants. For root tissue, acetone extraction was sufficient to recover a crude fraction of the polyphenols. For the seed tissue, an initial extraction with petroleum ether was used to remove triglycerides, followed by an extraction with acetone to recover the polyphenols. After concentrating the extracts, acetic acid was added to precipitate a crude mixture of the compounds (green in color). A second crystallization (from acetone and acetic acid) yielded a purer mixture of the compounds (yellow in color). Several preliminary attempts were made to separate the derivatives. Initial trials on silica thin-layer plates were unsuccessful because of smearing of the compounds along the stationary phase. Separation on the silica plates was achieved by derivatizing the gossypol aldehydes with ethyl-amine to form Schiff's bases. However, when scaled-up to an open column, some smearing of the compounds was still apparent that prohibited repeated use of the column. Pre-incubation of the silica with the diethylamine-gossypol reduced this problem, and separation of the dimethoxy-, methoxy-, and non-methylated gossypol was possible. The precoated column, however, was not chemically stable, turning a reddish color and resulting in a slow bleed of the contamination into the mobile phase. Separation was finally achieved by derivatization with 3-amino-1-propanol followed by chromatography in reverse-phase mode on a preparative high-pressure system. After repeated runs, acid was added directly to the fractions to hydrolyze the Schiff's base; the gossypol compounds were partitioned into diethyl-ether; and acetic acid was added to precipitate each product. The compounds will be tested for their anti-insect, anti-fungal, and anti-cancer activities.

Last Modified: 10/1/2014
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