Phenolic compounds alone or in combination may be involved in propolis effects on human monocytes

Objectives Propolis is a natural product with a complex chemical composition. Its isolated compounds exert biological activities; however, its synergistic effects are unknown. The involvement of phenolic acids (caffeic – Caf, dihydrocinnamic – Cin and p-coumaric – Cou) alone or in combination was investigated in the action of propolis in human monocytes. Methods Cell viability was analysed by MTT assay; TNF-α, IL-6 and IL-10 production by enzyme-linked immunosorbent assay (ELISA); cell markers expression by flow cytometry; colony-forming units were counted to assess the microbicidal activity; and H2O2 production was analysed by colorimetric assay. Key findings Treatments did not affect monocytes viability. Propolis and combinations containing Caf enhanced TNF-α production by resting cells. Propolis, Cin, Cou and Caf + Cin stimulated IL-6 production. All treatments upregulated IL-10. In LPS-stimulated cells, treatments downregulated IL-6 and maintained TNF-α and IL-10 production. A lower TLR-2 expression was seen than propolis. Caf + Cin enhanced TLR-4 expression. Propolis, Caf and Caf + Cin stimulated H2O2 production, whereas propolis, Cin, Cou, and Caf + Cin + Cou induced a higher fungicidal activity. Cin and Cin + Cou increased the bactericidal activity of human monocytes. Conclusion Propolis activated human monocytes, and acids were involved differently in propolis activity.