|Hron Sr, Robert|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/1999
Publication Date: N/A
Interpretive Summary: Cotton is grown throughout the southern United States for its valuable fiber. The plant also produces seed which is a valuable by-product. The seed can be fed directly to dairy cows to increase the percentage of milk fat or processed into an excellent edible oil used in cooking and salad dressings. After removing oil the resulting nutritious meal is also a valuable animal feed supplement. However, cottonseed contains a small amount of a substance called gossypol which can be toxic and cause male infertility in animals. In order to maximize cottonseed's use as an animal feed it is therefore important to determine gossypol's activity in animals. It is known that gossypol can exist in two forms in which the molecules contain the same number of identical atoms except that they are arranged differently. This difference in atom arrangement can make one form active and the other inactive. Cottonseed can contain different amounts of the active and inactive forms and it is important to be able to determine these amounts so that their effect on animals can be extensively studied. This paper describes a new simpler method for this determination.
Technical Abstract: Gossypol, a pigment in cottonseed, is a polyphenolic, bi-naphthyl dialdehyde. Due to stearic hindrance between the functional groups of the molecule at the bond connecting the two naphthyl rings, gossypol exists as (+)- and (-)-isomers. Gossypol is physiologically active with the (-)-isomer appearing to be more active and causing temporary infertility in males. It is thus important to know the amounts of isomers in livestock feeds. An HPLC procedure was developed for the separation of (+)- and (-)-gossypol contained in cottonseed. This method involves derivatization of gossypol with (R)-(-)-2-amino-1-propanol followed by HPLC separation employing either a Phenomenex, Prodigy, 5u, ODS-3, 100 X 3.2 mm or a MetaChem Inertsil, 5u, ODS-3, 100 X 3.0 mm reversed-phase column eluted with 80% acetonitrile and 20% 10 mM KH2PO4 adjusted to ph 3.0 with H3PO4 at 1.0 mL/min. The (+)- and (-)-gossypol-2-amino-1 -propanol complexes eluted at roughly 1.4 and 2.6 min, respectively. It was found that gossypol from Upland (Gossypium hirsutum) seed was rich in the (+)-enantiomer, with the (+)- and (-)-enantiomers in a ratio of about 65/35, respectively, while gossypol from the seed of a Pima (G. barbadense) cultivar (S-6) was slightly richer in the (-)-enantiomer (46.2/53.8).