Harzianic acid, a tetramic acid derivative, with activity of antimicrobial, antibiofilm formation and biofilm disaggregation. Harzianic acid interferes with biofilm formation by limiting bacterial iron availability. Harzianic acid is also a selective inhibitor of Acetohydroxyacid synthase (AHAS) , the first enzyme in the branched-chain amino acid biosynthetic pathway. Harzianic acid can used for herbicide and fungicide.