Aqueous extracts of cotton bracts induce a concentration dependent decrease in flow rates on partial expiratory flow volume curves. It has been shown that the active substance(s) is stable to moderate heat and to acid or alkaline conditions. Results of dialysis and gel filtration suggest that the active component(s) has a molecular size of about 1000 daltons. The component(s) is not absorbed on to ion exchange resins but is readily removed from aqueous extract by activated charcoal. The bronchoconstrictor agent cannot be steam distilled or extracted by ether. It is readily soluble in water; a single extraction of bracts removes all biologically active material. It is proposed that healthy subjects, responsive to cotton bracts extract, can be used qualitatively to fractionate and quantitatively to assay the active substance(s) in this material.
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