Comparative antioxidant capacities of the phenolic extracts of Lebanese floral and honeydew honeys -

Abstract

Thirty-one Lebanese honey samples including 16 honeydew and 15 floral samples, of diverse botanical origins, were collected from different regions of the country. The pH, electrical conductivity, moisture, protein, proline, hydroxymethylfurfural (HMF), color, melanoidins and Maillard-reaction products of the samples were determined. Moreover, the phenolic substances in the samples were extracted by solid phase extraction using XAD-2 resins. Furthermore, the total phenolic content and antioxidant capacities of the samples and their corresponding phenolic extracts were determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS) , and Superoxide Dismutase (SOD) antioxidant assays. The ranges of the samples were 3.67-5.67 for pH, 0.22-1.65 mS-cm for electrical conductivity, 13.72 - 20.20 percent for moisture, 66.08-242.88 mg Bovine Serum Albumin-100g of honey for protein, 169.39-1139.48 mg-kg for proline and 0.14-28.38 mg-kg for HMF. The color intensity of the honey samples ranged between 0.073 and 0.331 Absorbance Units (AU), the melanoidins contents ranged between 0.235 and 1.049 AU and the Maillard reaction products (MRPs) were between 0.381 and 1.804 AU. The results varied greatly within samples and honey type. Honeydew honeys showed a significantly higher (P0.001) pH value, electrical conductivity, color, MRPs and melanoidins than floral samples whereas floral honeys showed a significantly higher protein content than honeydew honeys (P0.05). The results for the total phenolics and antioxidant activity between honey samples and their extracts were found to be significantly different (P0.05). The total phenolics for floral honeys was significantly lower than that of honeydew honeys (P0.001). Moreover, the correlation coefficients between the antioxidant assays and total phenolic content were very high thereby indicating the importance of the phenolics in determining the antioxidant effects of honey. The antioxidant activities of honeydew and floral hone