Polyphenolic profile and in vitro immunomodulatory effect of Croatian native propolis

Propolis, the resinous product collected by honey bees from various plant sources, has been found to have numerous biological activities which are mainly attributed to the presence of polyphenolic compounds. Our study aimed to evaluate the polyphenolic composition and in vitro modulation effect of propolis on cytokines production. Four samples of raw propolis originated from the continental region of Croatia were analysed by reversed-phase HPLC-DAD method. The content of flavonoids (chrysin, galangin, apigenin, kaempferol, luteolin and naringenin), phenolic acids (caffeic, ferulic and coumaric acids) and caffeic acid phenyl ester (CAPE) significantly varied among examined samples and were in a wide concentration range between 0.13mg/g and 66.15mg/g. Modulation of cytokine production in concavalin A-stimulated splenocytes from Balb/C mice by propolis ethanolic extracts (0.3–90µg/mL), chrysin (0.1–30µg/mL) and CAPE (0.01–3µg/mL) was evaluated using the enzyme-linked immunosorbent assay (ELISA). Treatment of cells with the propolis extracts (≥10µg/mL) that contained high quantities of chrysin, galangin and CAPE significantly (85–100%) suppressed IL-4, lL-5, IL-10 and IFN-γ expression. Our results demonstrated that propolis affects the key messengers of immune response which play a very important role in the pathogenesis of immune system-associated diseases.