PHENOLIC-COMPOUNDS IN PEANUT SEEDS - ENHANCED ELICITATION BY CHITOSANAND EFFECTS ON GROWTH AND AFLATOXIN B-1 PRODUCTION BY ASPERGILLUS-FLAVUS

Effects of chitosan and Aspergillus flavus to enhance elicitation of p henolic compounds in viable peanut seeds were conducted at two water a ctivity levels. In vitro effects of phenolic acids on A. flavus growth and aflatoxin B, production were also studied. Chitosan enhanced elic itation of free phenolic compounds (FPC) at Aw .85 and .95 levels. A. flavus initially decreased and subsequently increased FPC content, but bound phenolic compounds (BPC) decreased during incubation. Chitosan + A. flavus treatment caused an increase in FPC reaching a plateau bet ween 24-48 h at Aw .85 while BPC levels increased over the same period at both Aw levels. Major free and bound phenolic acids detected were p-coumaric, ferulic and an unknown phenolic acid eluting at a retentio n time of 22 min. Generally, chitosan significantly enhanced elicitati on of free ferulic and p-coumaric acids and bound p-coumaric acid at A w .95. Free unknown phenolic and bound ferulic acids at Aw .85 were en hanced by chitosan. A. flavus caused significant induction of bound p- coumaric and ferulic acids and free unknown phenol at Aw .85. Chitosan + A, flavus enhanced free p-coumaric (3 h) and unknown phenolic acids and bound p-coumaric acid at Aw .95 while bound ferulic acid was enha nced at Aw .85. Chitosan Limited A. flavus growth and subsequent aflat oxin production by inducing susceptible tissues to produce more prefor med phenolic compounds. Analysis of Liquid cultures of A. flavus revea led that p-coumaric, ferulic, and vanillic acids and a mixture of thes e phenolic acids slightly inhibited mycelial growth. Production of afl atoxin B-1 by A. flavus was completely inhibited at 1 mM and 10 mM con centrations of the phenolic acids and their mixture on four days of in cubation. Mode of action of phenolic acids is likely on the secondary pathway for aflatoxin B-1 production and not on the primary metabolism for fungal growth.