Standardization of antioxidant properties of honey by a combination of spectrophotometric/fluorimetric assays and chemometrics

The aim of this work was to establish a solid platform of analytical information for the definition/standardization of the antioxidant properties of honey. We investigated first the antioxidant/radical scavenging capacity of 14 commercial honeys of different floral and geographic origin, using a battery of spectrophotometric tests: Folin-Ciocalteu assay for phenol content (PC), ferric reducing antioxidant power (FRAP assay) for total antioxidant activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay for antiradical activity, absorbance:450 (ABS(450)) for color intensity and one fluorimetric method: ORAC, oxygen reactive antioxidant capacity for the antilipoperoxidant activity. Then the data from different procedures were compared and analysed by multivariate techniques (correlation matrix calculation, principal component analysis (PCA)). Significant correlations were obtained for all the antioxidant markers (r ranging from 0.933 to 0.716), with antioxidant properties strictly correlated to the phenolic content and honey color intensity. PCA found different clusters of honey based on the antioxidant power and very likely also on chemical composition. The results of this study demonstrated that only through a combination of antioxidant testings, comparative analyses, and chemometric evaluation we can achieve a strictly rigorous guideline for the characterization of the antioxidant activity of honey, an invaluable tool for the understanding/demonstration of its antioxidants linked therapeutic efficacy.