It is a yellow compound produced by the cotton plant that confers resistance to pests. Gossypol exists in two enantiomeric forms, (+) and (-), and is experimentally often used as a racemate, (±)-gossypol, or complexed with acetic acid. (±)-Gossypol is found in cottonseed and cottonseed products in two forms: free gossypol, which is readily extractable with solvents, and bound gossypol. The latter form represents mostly covalent adducts of gossypol to proteins, from which free gossypol can be (partially) liberated by heating with acids. Cottonseeds are by-products of cotton fiber production, and are rich in oil and proteins and are therefore used for cottonseed oil production and as a feed supplement. Storage, steam and heat, and extrusion of oil reduce free gossypol concentrations and commercial production of cottonseed meals with low levels of free gossypol is now achieved routinely with only 0.1-0.2% remaining as free gossypol.
Gossypol is moderately acute toxic in most species with oral LD50s of 2400-3340 mg/kg for rats, 500-950 mg/kg for mice, 350-600 mg/kg for rabbits, 550 mg/kg for pigs and 280-300 mg/kg for guinea pigs.
Signs of acute gossypol toxicity are similar in all animals and include dyspnoea and anorexia. Generally, (–)-gossypol is more biologically active than (+)-gossypol. However, (+)-gossypol is more slowly eliminated.
The main target organ of gossypol toxicity following repeated exposure to lower doses in rats and humans are the testes with reduced sperm motility, inhibited spermatogenesis and depressed sperm counts.
Suppressed spermatogenesis in humans is partly irreversible, particularly in males with varicocele. Gossypol also affects female reproductive organs and embryo development. Gossypol is not genotoxic and it did not induce tumours in a one year study in rat. No health-based guidance value (ADI, TDI) has been established for gossypol