Bioactive Peptides from Glanded and Glandless Cottonseeds

Cottonseeds are divided into glanded or glandless seeds depending on the presence or absence of pigment gossypol glands. Glanded cottonseeds from the most widely grown cotton plant compose of approximately 10% linters, 40% hulls and 50% kernels. Cottonseed kernels contain about 35% of oil and 40% of protein. Defatted commercial cottonseed meal from glanded seeds contains up to 1% residual gossypol, which limits its use of meals primarily to feed ruminants. Glandless cottonseeds do not contain pigment glands and have only trace amount of gossypol, whose protein may be useful as a food ingredient or as a feed for non-ruminant animals. Identification and utilization of bioactive peptides derived from cottonseed proteins would increase the value of cottonseeds. The objective of this study was to identify bioactive peptides in glanded and glandless cottonseed kernels. Cottonseeds were grounded into powder and extracted with alkaline media followed by treatment with chloroform/methanol to remove lipids. The pellet was suspended in 100 mM TrisCl. Seed protein (40 mg) was sonicated and treated with 8 M urea to denature the protein followed by digestion using trypsin (1/50 ratio, twice) at 37 ¢ªC overnight. The samples were neutralized with acetic acid to pH 7.4. SDS-PAGE showed that a similar pattern of polypeptide bands from both types of seeds. Tryptic peptides up to 80 ug/ml were used to treat mouse macrophages and cultured for 2-20 h. MTT assays showed that high concentrations of peptides from glanded kernels exhibited 30-40% of inhibition of mitochondrial activity of the immunological cells. Gene expression analysis was used to understand the molecular effects of bioactive peptides on a wide range of genes related to immunological responses and insulin signaling pathways. This study provides useful information on the potential value of peptides derived from cottonseeds and thus may increase the value of cottonseeds.