Function of the alkyl side chains of Deltalac-acetogenins in the inhibitory effect on mitochondrial complex I (NADH-ubiquinone oxidoreductase).

We synthesized a series of Deltalac-acetogenins in which the two alkyl side chains were systematically modified, and examined their inhibitory effect on bovine heart mitochondrial complex I (NADH-ubiquinone oxidoreductase). The results revealed that the physicochemical properties of the side chains, such as the balance of hydrophobicity and the width (or bulkiness) of the chains, are important structural factors for a potent inhibitory effect of amphiphilic Deltalac-acetogenins. This is probably because such properties decide the precise location of the hydrophilic bis-THF ring moiety in the enzyme embedded in the inner mitochondrial membrane.