Composition and Antioxidant Activity of Trigona carbonaria Honey from Australia

Abstract

Stingless bees (Tribe Meliponini) are a diverse group of highly eusocial bees distributed throughout the tropics and subtropics. Trigona carbonaria honey, from Australia, was characterized by traditional physicochemical parameters (acidity, sugars, diastase, electrical conductivity, hydroxymethylfurfural, invertase, nitrogen, and water content) and other compositional factors (flavonoids, polyphenols, organic acids, and water activity), as well as total antioxidant capacity and radical scavenging activity. For the Australian T. carbonaria, the traditional analytical parameters were similar to those previously reported for neotropical stingless bee honey and confirm that honeys produced by Meliponini bees possess several physicochemical properties that are distinctly different from Apis mellifera honey, with higher values of moisture (26.5 ± 0.8 g of water/100 g of honey), water activity (0.74 ± 0.01), electrical conductivity (1.64 ± 0.12 mS/cm), and free acidity (124.2 ± 22.9 mEq/kg of honey) and a very low diastase activity (0.4 ± 0.5 diastase number) and invertase activity (5.7 ± 1.5 invertase number). The sugar spectrum was quite different from that of A. mellifera honey, with 20.3 ± 2.9 g of maltose/100 g of honey. The values of pH (4.0 ± 0.1), lactonic acidity (4.7 ± 0.8 mEq/kg of honey), sucrose (1.8 ± 0.4 g/100 g of honey), and fructose/glucose ratio (1.42 ± 0.13) fell in the same ranges as those of A. mellifera honey. Citric (0.23 ± 0.09) and malic (0.12 ± 0.03) acid concentrations (in g/kg of honey) of T. carbonaria honeys were in the range described for A. mellifera honey. D-Gluconic was more concentrated (9.9 ± 1.3 g/kg of honey), in the range of Italian Castanea, Thymus, Arbutus, and honeydew honeys. Flavonoid content was 10.02 ± 1.59 mg of quercetin equivalents/100 g of honey, and polyphenol contents were 55.74 ± 6.11 mg of gallic acid equivalents/100 g of honey. The antioxidant activity, expressed as percentage of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) cation (ABTS^.+) decolorization, was 233.96 ± 50.95 μM Trolox equivalents, and free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH^.) depletion was 48.03 ± 12.58 equivalents of ascorbic acid. All reported values are averages ± standard deviation. The antioxidant activity can represent an important added value for T. carbonaria honey, to initiate a medicinal approach for both nutritional and pharmaceutical applications, besides further physicochemical characterization.