Abstract
The phenolic acid profile of honey depends greatly on its botanical and geographical origin. In this study, we carried out a quantitative analysis of phenolic acids in the ethyl acetate extract of 12 honeys collected from various regions in Greece. Our findings indicate that protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid and p-coumaric acid are the major phenolic acids of the honeys examined. Conifer tree honey (from pine and fir) contained significantly higher concentrations of protocatechuic and caffeic acid (mean: 6640 and 397 µg/kg honey respectively) than thyme and citrus honey (mean of protocatechuic and caffeic acid: 437.6 and 116 µg/kg honey respectively). p-Hydroxybenzoic acid was the dominant compound in thyme honeys (mean: 1252.5 µg/kg honey). We further examined the antioxidant potential (ORAC assay) of the extracts, their ability to influence viability of prostate cancer (PC-3) and breast cancer (MCF-7) cells as well as their lowering effect on TNF- α-induced adhesion molecule expression in endothelial cells (HAEC). ORAC values of Greek honeys ranged from 415 to 2129 µmol Trolox equivalent/kg honey and correlated significantly with their content in protocatechuic acid (p<0.001), p-hydroxybenzoic acid (p<0.01), vanillic acid (p<0.05), caffeic acid (p<0.01), p-coumaric acid (p<0.001) and their total phenolic content (p<0.001). Honey extracts reduced significantly the viability of PC-3 and MCF-7 cells as well as the expression of adhesion molecules in HAEC. Importantly, vanillic acid content correlated significantly with anticancer activity in PC-3 and MCF-7 cells (p<0.01, p<0.05 respectively). Protocatechuic acid, vanillic acid and total phenolic content correlated significantly with the inhibition of VCAM-1 expression (p<0.05, p<0.05 and p<0.01 respectively). In conclusion, Greek honeys are rich in phenolic acids, in particular protocatechuic and p-hydroxybenzoic acid and exhibit significant antioxidant, anticancer and antiatherogenic activities which may be attributed, at least in part, to their phenolic acid content.
Highlights
Honey is a highly nutritious natural food product which has been used in various medicinal traditions throughout the world for its healing, antibacterial and antiinflammatory properties
Examination of the HPLC chromatogram of honey ethyl acetate extracts revealed that Greek honeys are rich in phenolic acids
Protocatechuic and caffeic acid levels were higher in pine and fir honey when compared to thyme or citrus honey. p-Hydroxybenzoic acid was the dominant constituent in thyme honeys
Summary
Honey is a highly nutritious natural food product which has been used in various medicinal traditions throughout the world for its healing, antibacterial and antiinflammatory properties. Emerging evidence suggests that honey possesses chemopreventive, antiatherogenic and immunoregulatory properties as well as a great potential to serve as a natural food antioxidant [1,2,3,4,5,6,7]. Phenolic acids like caffeic acid and pcoumaric acid in chestnut honey as well as protocatechuic acid in honeydew honeys have been used as floral markers [14,15]. Phenolic acids are compounds with multiple biological activities, including anticancer, antiinflammatory, antioxidant and antiatherogenic properties. Hydroxybenzoic acid derivatives like phydroxybenzoic, protocatechuic and vanillic acid as well as hydroxycinnamic acid forms like p-coumaric and caffeic acid, are components with important anticancer activity [16,17]. Protocatechuic and caffeic acid have been shown to exhibit a significant potential as antidiabetic and cardioprotective agents [18,19,20]
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