Comparative analysis of antioxidant profile, protein, and proline content in oak honeydew and oak honeydew-nectar honey from Northwestern Greece

Aim: This study aimed to evaluate and compare the antioxidant activity, phenolic and flavonoid content, proline, and protein levels of oak honeydew and oak honeydew-nectar honeys produced in Northwestern Greece, providing the first comparative compositional data for these honey types. Methods: Thirty-four honey samples (16 oak honeydew and 18 oak honeydew-nectar) were collected from the region of Western Macedonia during the 2021–2022 harvest seasons. Total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (DPPH and FRAP assays), colour intensity (ABS450), and proline and protein contents were determined using spectrophotometric methods. Statistical analyses included independent-samples t-tests, Pearson correlation analysis, and multivariate techniques (PCA and hierarchical clustering) to assess variation and grouping patterns between honey types. Results: Oak honeydew honey showed higher TPC (137.52 vs. 115.69 mg GAE/100 g), antioxidant activity (DPPH: 20.26 vs. 15.24% inhibition; FRAP: 53.25 vs. 41.26 μΜ TE/100 g), and colour intensity (ABS450: 802 vs. 623.3 mAU) compared with oak honeydew-nectar honey (P < 0.05). TFC (51.67 vs. 42.22 mg RUE/100 g), proline (965.62 vs. 1,095.68 mg/kg), and protein contents (0.24 vs. 0.27 mg/g) were similar between oak honeydew and oak honeydew-nectar honey, respectively, with no significant differences (P > 0.05). Correlation analysis revealed strong positive associations among antioxidant activity, colour intensity, and flavonoid content, while protein exhibited inverse correlations with antioxidant parameters in oak honeydew honey but positive ones in oak honeydew-nectar honey. PCA showed a clear differentiation trend between the two honey types. Conclusions: Oak honeydew honey exhibited superior antioxidant capacity and phenolic content, reflecting a richer bioactive composition. These findings provide the first comparative insight into Greek oak honeys and highlight their practical significance for honey authentication, quality evaluation, and consumer awareness of honeydew honeys produced in Northwestern Greece.