Quantitate Gossypol Enantiomers in Cotton Flower Petals and Seed Using Capillary Electrophoresis

Gossypol is a compound that occurs in the cotton plant.  In the foliage it protects the plant from insect herbivory.  The compound also occurs in the seed.  In this tissue it renders the seed toxic to non-ruminant animals.  However, gossypol exists as a mixture of enantiomers referred to as (+)-gossypol and (-)-gossypol.  The (‑)‑enantiomer is more toxic to non-ruminant animals. We have developed cotton plants with a low level of (-)-gossypol in the seed.  The seed from these plants are less toxic to chickens than normal cottonseed.  To breed plants with the low (‑)‑gossypol seed trait, the percentage of (+)- and (-)-gossypol must be determined in the flower petals and seed.  This can be accomplished using high performance liquid chromatography (HPLC).  We now report a method to quantitatively determine the total gossypol and percent of its enantiomers in cotton tissues using high performance capillary electrophoresis (HPCE).  The method utilizes a borate buffer at pH 9.3 using a capillary with internal diameter of 50 μ, effective length of 24.5 cm, 15 kV and cassette temperature of 15°C.  This method uses less expensive solvents than those used in HPLC and provides high accuracy and reproducible results with a limit of detection of the individual enantiomers of less than 36 ng/mL providing base line separation in less than 6 minutes.