ANTIOXIDANT ACTIVITIES OF LIGNANS AND FLAVONOIDS

The antioxidant activity of lignans and flavonoids was assessed by their effects upon the rate of rat brain homogenate autoxidation. The structurally similar lignans dihydroguayaretic acid, guayacasin and isopregomisin are powerful antioxidants with activities similar to that of propyl gallate. The differences observed between the different lignans (a factor of four between dihydroguataretic acid and isopregomisin) can be explained in terms of the number of methoxyl groups of each compound. The flavonoids 3′-methoxycalicopterin and 7′-methylsudachitin are considerably less active than the lignans or quercetin. Differences observed in their antioxidant capacities assessed from luminescence and TBAR determinations, indicate that visible luminescence is not an appropriate method for assessing the antioxidant capacities of flavonoids or additives absorbing at wavelengths close to those of emission of the excited states involved. © 1990.