Characterization of Immunomodulatory Activities of Honey Glycoproteins and Glycopeptides

Recent evidence suggests an important role for natural honey in modulating immune response. To identify active components responsible, this study investigated the immunomodulatory properties of glycoproteins and glycopeptides fractionated from Ziziphus honey. Honey proteins/peptides were fractionated by size exclusion chromatography into five peaks with molecular masses in the range of 2–450 kDa. The fractionated proteins exhibited potent, concentration-dependent inhibition of reactive oxygen species production in zymosan-activated human neutrophils (IC50 = 6–14 ng/mL) and murine macrophages (IC50 = 2–9 ng/mL). Honey proteins significantly suppressed the nitric oxide production by LPS-activated murine macrophages (IC50 = 96–450 ng/mL). Moreover, honey proteins inhibited the phagocytosis latex bead macrophages. The production of pro-inflammatory cytokines IL-1β and TNF-α by human monocytic cell line in the presence of honey proteins was analyzed. Honey proteins did not affect the production of IL-1β; however, TNF-α production was significantly suppressed. These findings indicated that honey glycoproteins and glycopeptides significantly interfere with molecules of the innate immune system.