Assessment of Antioxidant Properties of Honeys from Tanzania

Abstract

In this study, levels and properties of antioxidants, antiradical and iron chelating activities of honeybee and stingless bee honeys were determined using standard methods. The relationship between honey colour and the studied antioxidants was also explored. Phenolic content of stingless bees honey samples (mean value 847.6 mgGAE/100g) was significantly higher (P<0.0001) than that of raw (412.6 mgGAE/100g) and processed (218.4 mgGAE/100g) honeybee honey samples, respectively. Mean value of flavonoid content was 84.96 mgRE/100g for stingless bee honeys, 44.82 mgRE/100g for processed honeybee honeys and 41.60 mgRE/100g for raw honeybee honeys. ?-Carotene and lycopene content varied among the three honey categories studied. Honey from stingless bees exhibited higher levels of the two antioxidants than honey bee honeys. Vitamin C content ranged from 20.4 – 66.7 mg/100g in processed honey, 42.5 – 61.6 mg/100g in raw honeybees honey and from 56.2 – 67.6 mg/100g in stingless bee honeys. The number of antiradical activity units in 1 mg of honey (EAU₅₁₅) varied significantly between the honey categories (P<0.0001). The mean values were 5.21 mg/100g for processed honeybee honeys, 6.8 mg/100g for raw honeybee honeys and 10.6 mg/100g for stingless bee honeys. DPPH radical scavenging and iron chelating activities were highest (lowest EC₅₀) in stingless bee honeys compared to honeybee honeys. EC₅₀ mean value for DPPH was lowest (4.19 mg/ml) in stingless bee honeys, 12.93 mg/ml for raw honeybees honey and 18.03 for processed honeybees’ honey.  Similarly, iron chelating activity was highest in stingless bee honeys (EC₅₀ 0.04 mg/ml) followed by raw honeybee honeys (EC₅₀ 0.057 mg/ml) and processes honeybee honeys (EC₅₀ 0.158). A diversity of honey colours ranging from light coloured to dark honeys was recorded in the samples studied. Majority of honeybee honey colours were described as white and light amber, while all the stingless bee honeys were between light amber and amber colours. There were strong positive correlations among the antioxidants studied (r ? 0.5 at P<0.01). Honey colour intensity was found to correlate positively with all antioxidants studied. Consistently darker honeys were found to contain higher levels of antioxidants than lighter honeys. In overall, Tanzanian honeys studied contains high levels of antioxidants, depicting good quality characteristics for use as food and as medicine.

Key words: Antioxidants, DPPH, Antiradical activity, Phenolics, Flavonoids