Inhibition of soybean lipoxygenases by resorcinolic lipids from cereal bran

Incubation of soybean lipoxygenase isoenzymes (L-1, L-2, and L-3) with total resorcinolic lipids isolated from wheat bran or their purified homologs (5-n-pentadecylresorcinol and 5-n-tricosylresorcinol) led to apparent inhibition of all three isoenzyme activities. The IC50 values determined for studied compounds showed that the inhibitory activity was related to the length of the resorcinolic lipid aliphatic chain and was more effective for homolog with longer chain attached to 1,3-dihydroxybenzene ring in metha position. Similar dependence on the length of the alkylresorcinol side chain was observed also for Ki values. The 5-n-tricosylresorcinol (23:0 AR) was found to be the most efficient inhibitor of soybean lipoxygenases with IC50 values in the range of several µM regardless of the substrate used (linoleic acid or arachidonic acid). All alkylresorcinols studied caused increase of apparent KM values and decrease of VMAX values of the enzymes thus suggested the mixed type of lipoxygenase inhibition.