Food Chemistry, Article in Press
The antioxidant activity of several honeys was evaluated considering the different contribution of entire samples.
The strawberry tree honey emerged as the richest in total phenols and the most active honey in the DPPH and FRAP tests, and could protect cholesterol against oxidative degradation (140 °C). Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA), the main phenolic compound from strawberry tree honey, showed interesting antioxidant and antiradical activities, and protective effect against thermal-cholesterol degradation, comparable to those of well known antioxidants.
Moreover, the pre-treatment with HGA significantly preserved liposomes and LDL from Cu2+-induced oxidative damage at 37 °C for 2 h, inhibiting the reduction of polyunsaturated fatty acids and cholesterol and the increase of their oxidative products. This phenol had no toxic effect in human intestinal epithelial Caco-2 cells within the concentration range tested (5–1000 μM). HGA was able to pass through the Caco-2 monolayers, the apparent permeability coefficients (Papp) in the apical-to-basolateral and basolateral-to-apical direction were 3.48 ± 1.22 × 10-6 and 2.18 ± 0.34 × 10-6 cm/s, respectively, suggesting a passive diffusion pathway as the dominating process.
The results of the work qualify HGA as natural antioxidant, able to exert a significant in vitro protective effect and to contribute to the strawberry tree honey antioxidant activity.
Highlights
• Strawberry tree honey protected in DPPH/FRAP tests, and cholesterol from degradation.
• Homogentisic acid, main phenolic compound of strawberry tree honey.
• The phenol protected in DPPH/FRAP tests, and cholesterol/fatty acids from oxidation.
Homogentisic acid showed no toxicity and passive diffusion in Caco-2 cell monolayers.
• Contribution of homogentisic acid to antioxidant activity of strawberry tree honey.
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