Influence of the interactions between tea (Camellia sinensis) extracts and ascorbic acid on their antioxidant activity: analysis with interaction indexes and isobolograms

Abstract

Products containing natural additives, including antioxidants, are usually perceived by consumers as safer than those with synthetic ones. Natural antioxidants, besides having a preservative activity, may exert beneficial health effects. Interactions between antioxidants may significantly change their antioxidant activity, thus in designing functional foods or food/cosmetic ingredients knowledge about the type of interactions could be useful. In the present study, the interactions between ascorbic acid (AA; vitamin C) and different black and green tea extracts and the influence on their antioxidant activities were investigated. The antioxidant activities of tea extracts and their mixtures with AA prepared in several different weight ratios were measured using the trolox equivalent antioxidant capacity (TEAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and ferric-reducing antioxidant power (FRAP) methods. The type of interaction was determined by interaction indexes and isobolograms. It was found that the weight ratio of extracts to AA significantly influenced the antioxidant activity of a mixture and the type of interaction between these components. The weight ratio of tea extract to AA can cause the change of interaction, e.g. from antagonism to additivism or from additivism to synergism. The observed differences in the type of interactions were probably also a result of different extracts' polyphenol composition and content. The type of interaction may also be affected by the medium in which extracts and AA interact, especially its pH and the solvent used. To obtain the best antioxidant effect, all these factors should be taken into account during the design of a tea extract-AA mixture.

Effects of Infusion and Storage on Antioxidant Activity and Total Phenolic Content of Black Tea

“…Theaflavins, a type of phenolic compound in black tea, may contribute to strong antioxidant properties that affect the DPPH scavenging activity and total phenols [23,[29][30][31][32]. However, the therapeutic activities of black tea are attributed not only to the antioxidant activity of its components but also to the ability of bioactive molecules to interact with several biological targets [33,34]. At a high temperature, chemical degradation can occur, changing the structure of temperature-sensitive molecules such as (-)-epigallocatechin-3-gallate.…”

“…Wide variations are noted among different kinds of black tea in terms of DPPH scavenging ability [9,22,[34][35][36][37][38] and total phenolic content [6,20,32,36,39]; these are highly dependent on the genetic background and growing conditions (such as temperature, nitrogen availability, and light conditions) of the plant material. The IC 50 of black tea in this study was 28.4 ± 4.8 µg/mL, and it falls within the range of 12.7-118.7 µg/mL found by other authors [34,38]. The total phenolic content in this study was 178.6 ± 16.4 mg GAE/g dry leaf, and it was in the range from 50.9 ± 4.1 mg GAE/g dry leaf [32] to 274.3 ± 0.0 mg GAE/g dry leaf [20].…”

Investigation of antioxidant activity of selenium compounds and their mixtures with tea polyphenols

“…Lower [36], higher [15] or similar [38] value have been reported. On the other hand, there is well known that polyphenols as well as other bioactive compounds could interact between each other, which is clearly visible in the antioxidant activities of their mixtures [3,8,11,20]. Mouly et al [17] reported that over 300 remedies and mineral supplements are capable of interacting with food components through essential mineral antagonism, induction of inhibition of micronutrient metabolism.…”

Characterization of Fulvic Acid Beverages by Mineral Profile and Antioxidant Capacity

“…The antioxidant capacity of fulvic acid products was determined using the TEAC method with ABTS •+ radical cation as described by Re et al [25]. Moreover, the FRAP assay was carried out by the method of Benzie and Strain [26] with modifications previously described [27].…”

“…A volume of 0.008 mL of sample was added to 0.792 mL of the 10 mM ferric-TPTZ reagent and the increase in absorbance at 593 nm was measured after 8 min. The FRAP value was calculated as the ratio of the linear regression coefficient of the calibration curve for five dilutions of the sample and the linear regression coefficient of the FeSO 4 × 7 H 2 O standard curve [27]. Three independent determinations were performed for each sample.…”