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Title: HPLC Preparation of the Chiral Forms of 6-Methoxy-Gossypol and 6,6'-Dimethoxy-Gossypol

item Dowd, Michael
item Pelitire, Scott

Submitted to: Journal of Chromatography B
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2008
Publication Date: 3/25/2008
Citation: Dowd, M.K., Pelitire, S.M. 2008. Hplc preparation of the chiral forms of 6-methoxy-gossypol and 6,6'-dimethoxy-gossypol. Journal of Chromatography B. 867:69-77.

Interpretive Summary: A method was developed to recovery the individual optical forms of methoxy and dimethoxy-gossypol from the root bark of Sea Island cotton. Gossypol is a natural product with a wide array of biological activity, including anti-tumor, anti-fertility, anti-fungal and insecticidal effects. The methoxy derivatives of gossypol are found in high concentrations in only a few cotton varieties and are difficult to separate from gossypol. The proposed isolation method should be interest to researchers studying the bioactivity of natural products.

Technical Abstract: A concentrated mixture of gossypol, 6-methoxy-gossypol and 6,6'-dimethoxy-gossypol was extracted with acetone from the root bark of St. Vincent Sea Island cotton. This extract was derivatized with R-(-)-2-amino-1-propanol to form diastereomeric gossypol Schiff’s bases. Analytical-scale reverse-phase chromatography of these Schiff’s bases produced six peaks, indicating separation of the enantiomeric forms of the three gossypol compounds. The elution order of the peaks was found to vary with the polarity of the mobile phase. The chromatography was scaled to a preparative level and was used to isolate each compound. After hydrolysis of the Schiff’s bases, the original compounds were recovered by precipitation from a solution of diethyl ether, acetic acid, and water. Each compound was characterized for carbon and hydrogen content, optical rotation, UV-visible light absorption, and melting point. Standard curves were developed for each compound and were used to measure the concentration of each gossypol derivative in the root bark and dehulled seed of St. Vincent Sea Island cotton.