Flavonoid combinations cause synergistic inhibition of proinflammatory mediator secretion from lipopolysaccharide-induced RAW 264.7 cells

We evaluated several flavonoid combinations for synergy in the inhibition of proinflammatory mediator synthesis in the RAW 264.7 cellular model of inflammation. The inhibitory effect of chrysin, kaempferol, morin, silibinin, quercetin, diosmin and hesperidin upon nitric oxide (NO), prostaglandin E-2 (PGE(2)) and tumour necrosis factor-alpha (TNF-alpha) secretion from the LPS-induced RAW 264.7 monocytic macrophage was assessed and IC50 values obtained. Flavonoids that showed reasonable inhibitory effects in at least two out of the three assays were combined in a series of fixed IC50 ratios and reassessed for inhibition of NO, PGE(2) and TNF-alpha. Dose-response curves were generated and interactions were analysed using isobolographic analysis. The experiments showed that only chrysin, kaempferol, morin, and silibinin were potent enough to produce dose-response effects upon at least two out of the three mediators assayed. Combinations of these four flavonoids showed that several combinations afforded highly significant synergistic effects. Some flavonoids are synergistic in their anti-inflammatory effects when combined. In particular chrysin and kaempferol significantly synergised in their inhibitory effect upon NO, PGE(2) and TNF-alpha secretion. These findings open further avenues of research into combinatorial therapeutics of inflammatory-related diseases and the pharmacology of flavonoid synergy.