Silica Gel Chromatographic Methods for Identification, Isolation and Purification of Gossypol Acetic Acid.

Several cottonseed varieties are cultivated in different countries. Each variety produces a different amount of gossypol as a natural toxic compound. The rising interest in cottonseed products (oil and feed) increases the demand for establishing simple methods for gossypol detection. Silica gel-based methods are ideal for its isolation, purification, and characterization. Silica gel-based methods are variants and can be used as simple methods for tracking plants' compounds. In this study, gossypol was isolated, characterized, and purified as gossypol acetic acid in the form of yellow crystals. Methods used for its characterization were TLC, preparative TLC, silica gel column, UV/IR spectrophotometer, and HPLC (robust spherical silica gel). A comparative study between its amount in both the Egyptian and Chinese varieties was performed. Under the experimental conditions, the Egyptian's cottonseed contains 8.705 gm/kg, while the Chinese's cottonseed contains 5.395 gm/kg. The TLC used in this study proved to be fast, accurate, and inexpensive. It can be used for gossypol acetic acid evaluation and quantification. Additionally, using TLC as a pre-purification step will give a pre-judgment for the sample's purity and quality. This step will protect the expensive HPLC silica gel-based column from any unexpected impurities. During each step, the silica gel itself could be simply removed by paper filtration. Collectively, the different silica gel-based methods as well as the other used methods are recommended for better Gossypol acetic acid isolation, purification, and characterization, as well as for maintaining HPLC columns.