Bee pollen is a health food with nutritional and therapeutic properties. The aim of this work was to evaluate free radical scavenging activity (FRSA) in selected samples obtained from local beekeepers in Castelo Branco (Portugal). The identification of the floral origin was performed using acetolysis method.
Each sample of bee pollen (0.10 ± 0.01 g) was extracted with methanol, ethanol and water [1, 2] to evaluate which solution provided the best extract. All the experiments were analysed in quadruplicate. The total polyphenol content of bee pollen was analysed by spectrophotometry at 725nm using the Folin-Ciocalteu reagent with ferulic acid as a standard. FRSA was evaluated according to the DPPH · and ABTS ·+ methods.
In relation to the content of total polyphenols, the FRSA values varied considerably. Different floral species present species-specific activity [1] but these are dependent on the analytical method and the extraction solvent. On average, the highest polyphenol content was observed in methanol bee pollen extracts with the exception of the mixture B and the Echium sp. pollen (Table 1). For the total FRSA with DPPH and ABTS methods, ethanol pollen extracts show higher activity with the exception of Trifolium spp. where the aqueous extract gives the higher result (Table 1). Mixture B and C ethanolic extracts give the best FRSA values.
The ANOVA shows for the three methods that there are significant differences between solvent extracts and protocols, however the variation between the solvent extracts is similar in the different procedures.
Tab. 1: Polyphenol content and free radical scavenging activity of pollen extracts in different solvents
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Extract
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Echium sp.
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Trifolium spp.
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Mixture A
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Mixture B
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Mixture C
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Polyphenol content (FAE/100 g pollen)
|
Water
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51.38 ± 0.21cB
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29.85 ± 0.17aA
|
86.75 ± 0.19bE
|
72.90 ± 0.18aD
|
62.50 ± 0.12bC
|
|
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Ethanol
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29.63 ± 0.17aC
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86.30 ± 0.12bE
|
42.08 ± 0.25aD
|
11.60 ± 0.16aB
|
10.70 ± 0.12aA
|
|
|
Methanol
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45.93 ± 0.15bA
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86.75 ± 0.19bC
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118.20 ± 0.12cD
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61.93 ± 0.26bB
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86.38 ± 0.28cC
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|
% DPPH Inhibition
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Water
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12.03 ± 0.59aA
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8.13 ± 0.36aA
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30.26 ± 1.04aC
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21.05 ± 0.79cB
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25.24 ± 0.83bB
|
|
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Ethanol
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10.78 ± 0.45aC
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41.62 ± 1.11bE
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28.03 ± 2.23aD
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4.02 ± 0.30aA
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2.53 ± 0.12aA
|
|
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Methanol
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11.72 ± 0.24aA
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61.91 ± 1.51cC
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64.30 ± 2.84bC
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15.68 ± 0.98bA
|
45.09 ± 1.74cB
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|
% ABTS Inhibition
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Water
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17.10 ± 0.67bA
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20.38 ± 0.72aB
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37.37 ± 0.67bD
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33.89 ± 1.63cC
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32.82 ± 0.76bC
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|
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Ethanol
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13.39 ± 0.47aB
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24.89 ± 0.57bD
|
18.31 ± 0.63aC
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6.51 ± 0.32aA
|
6.11 ± 0.07aA
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|
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Methanol
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17.00 ± 0.30bA
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39.93 ± 1.24cC
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38.63 ± 1.37bC
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22.47 ± 0.61bB
|
37.24 ± 1.25cC
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a. d, c mean values with different letters in a column for each method differ statistically (p < 0.05); A, B, C, D, E mean values with different letters in a line differ statistically (p < 0.05).
Mixture A:
Cistus spp.; Quercus spp.; Olea spp; Brassica spp.; Raphanus spp.; Mixture B:
Taraxacum spp.; Andryala spp.;
Cistus spp., Rhamnus spp.; Mixture C:
Cistus spp. (majority); Crepis spp.; Trifolium spp. (minority).
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References:
[1] Campos MG, Webby RF, Markham K R, Mitchell KA, Cunha AP. Age-induced diminution of free radical scavenging capacity in bee-pollens and the contribution of constituent flavonoids. J Agric Food Chem 2003; 51: 742 – 745
[2] Pérez-Pérez EM, Vit P, Rivas E, Sciortino R, Sosa A, Tejada D, Rodríguez-Malaver AJ. Antioxidant activity of four color fractions of bee pollen from Mérida, Venezuela. Arch Latinoam Nutr 2012; 62: 375 – 380
