Inhibition of mitochondrial energy-linked reactions by 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (dimboa), a hydroxamic acid from gramineae

DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is the main hydroxamic acid isolated from maize extracts. It inhibited reversibly ATP synthesis, P I-ATP exchange reaction and ATPase activity in submitochondrial particles from bovine heart. Half-maximal effects were obtained with 4, 2, and 6 mM DIMBOA respectively. At higher concentrations it also inhibited mitochondrial electron transport ( I 50 = 11 mM). Irreversible inactivation of mitochondrial electron transport, P i-ATP exchange reaction and 8-anilino-1-naphthalene sulfonate energy-dependent fluorescence enhancement was also observed. These effects of DIMBOA on energy-linked mitochondrial reactions may explain the inhibitory action of DIMBOA on several aerobic organisms.