DEMONSTRATION OF AFLATOXIN INHIBITORY ACTIVITY IN A COTTON SEED COAT XYLAN

An inhibitor of aflatoxin biosynthesis localized in the seed coats of developing cotton was partially purified and characterized, Aqueous ex tracts from 25-day postanthesis seed coat tissue inhibited aflatoxin ( B-1) production in liquid cultures of Aspergillus flavus AF13, Inhibit ion was concentration dependent, with a 50% effective dose of 173 mu g of crude extract per ml of medium, The inhibitor was neutral in charg e, Two active fractions mere obtained from crude preparations by gel f iltration chromatography (BioGel P-100). The purest fraction eluted in the void volume, Carbohydrate composition analysis of this void volum e inhibitor indicated a composition of xylose (>90%) and mannose, Afla toxin production in vitro was inversely related to inhibitor concentra tion in the fermentation medium (log of aflatoxin versus log of [inhib itor]; r(2) = 0.82; P < 0.002). The void volume inhibitor had a 50% ef fective dose of 6.2 mu g/ml, a 28-fold purification of the inhibitor m aterial, These data support the hypothesis that seed coat inhibitory a ctivity is associated with a cottonseed-specific xylan.