Abstract
Antioxidant activity was measured by ferric reducing ability of plasma (FRAP) assay in seven types of infusions prepared from commercial dried berry fruit products: Rosa canina , Vaccinium vitis-idaea , Hiphophae rhamnoides , Hibiscus sabdariffa and three fruit mixtures. Total polyphenols (TP), total anthocyanins and the polyphenolic compounds were determined by HPLC equipped with diode array detector. To estimate the amount of elements released from fruits into the water extracts, levels of Fe, Mn, Zn and Cu in dried samples and in infusions were determined by flame atomic absorption spectrometry. The correlation between polyphenols content and the antioxidant activities and the microelements in the infusions and the antioxidant activities were estimated using the Pearson’s correlation test. The results showed a high, positive and significant correlation (r = 0.9465) between the FRAP values and TP content, meaning that the concentration of phenolic compounds may be a good indicator of the reducing capacity in the infusions. Correlations varied (positive, negative and weak) between antioxidant and mineral extractability of berry infusions. Among the polyphenolic compounds, gallic acid contributed particularly to the antioxidant capacity of the studied samples (r = 0.563). The correlation of antioxidants, total polyphenols with mineral extractability showed the influence of antioxidant compound on mineral bioavailability. KEY WORDS : Mixed berry infusion, Antioxidant activity, Phenolic compounds, Microelements Bull. Chem. Soc. Ethiop. 2018 , 32(1), 1-12 DOI: https://dx.doi.org/10.4314/bcse.v32i1.1
Highlights
Berry fruits are an important source of phytonutrients with considerable health benefits for human
The order of ferric reducing ability of plasma (FRAP) values was as follows: Rosa canina dried fruits (BT1) > mixtures of dried berries (BT5, BT6, BT7) > Hibiscus sabdariffa dried calyces (BT4) > Hiphophae rhamnoides fruits (BT3) > Vaccinium vitis-idaea fruits (BT2). These results indicate that the antioxidants present in the rose hip infusion (BT1) are in the highest amount, which is in agreement with the total polyphenolic compounds content found in this type of infusion
In order to evaluate the contribution of phenolic compounds to the antioxidant activity of berry infusions, correlation coefficient was calculated. These was a strong, positive and significant correlation (r = 0.9465) between the FRAP values and Total polyphenols (TP) content meaning that the concentration of phenolic compounds may be a good indicator of the reducing capacity in the infusions
Summary
Berry fruits are an important source of phytonutrients with considerable health benefits for human. Due to their high content in vitamins, phenolic compounds and minerals, they are widely recommended in the healthy human diet [1, 2]. Measurements of antioxidant activity using different methods in berry fruits lead to the conclusion that they have considerable high antioxidant capacity [3, 4]. It is considered that many of the health benefits associated with berry fruits dietary intake are linked to their high polyphenols content. A mixture of berry/wild fruits is used in winter time, to prepare various beverages considered as having both nutritional and therapeutic benefits. The traditional tisanes prepared by infusing the dried berry/wild fruits are nowadays rediscovered and plenty of commercial products containing dried berry/wild fruits promote their antioxidant effects against degenerative chronic diseases such as cancer, diabetes and atherosclerosis [1]
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