Stability of the gossypol-amine adducts used for chromatographic measurement of total and isomeric gossypol

Authors: Dowd, Michael

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2020
Publication Date: 4/8/2020
Citation: Dowd, M.K. 2020. Stability of the gossypol-amine adducts used for chromatographic measurement of total and isomeric gossypol. Journal of the American Oil Chemists' Society. 97(6):671-675. https://doi.org/10.1002/aocs.12355.
DOI: https://doi.org/10.1002/aocs.12355

Interpretive Summary: Gossypol is a component of cottonseed with antinutritive effects that limit the use of seed and meal. Because the compound readily binds to other seed components, measurement of the compound uses chemistry to form a single gossypol complex that can be detected by liquid chromatography. The stability of these complexes has not been studied but is important, e.g., if samples need to be shipped between laboratories for analysis. In this work, the stability of the most common gossypol complex was studied when stored at different conditions and times. The complex was stable when stored in the dark below -20 C for up to 30 days, but was not stable at higher temperatures. The results can be used to provide recommendations (e.g., in the dark on dry ice) for how the complex can be transported between laboratories.

Technical Abstract: The stability of the amine complex used for chromatographic determination of gossypol was studied. After complexation with R-(-)-2-amino-1-propanol and dilution into HPLC mobile phase (acetonitrile/phosphate buffer solution), as is described in AOCS Recommended Practice Ba 8a-99, the solutions were stored in different conditions for up to 30 days to study their stability. The rate of degradation did not differ for different samples studied (i.e. cottonseed kernels, defatted cottonseed meal, and pure gossypol acetic acid). Nor was the rate of degradation different for the individual gossypol enantiomers. Samples stored in the dark at -80 °C or -20 °C exhibited little degradation over the 30 days of study. Samples stored in the dark at -4 °C or room temperature showed measurable degradation. Samples stored in the light at room temperature degraded the fastest with only 25% of the initial gossypol detectable at the end of the study period. The rate of degradation followed first-order kinetics. The results indicate that the derivatized gossypol samples can be transported on dry ice with minimal concerns regarding the stability of the samples.