## 3 Results and Discussion
(**A**) Isobole curve for chlorogenic and ferulic acids, (**B**) LPO potential of buffer extractable (BE), bioaccessible (DE), and bioavailable (AE) green coffee beans, and wholeemal wheat flour compounds and pure ferulic and chlorogenic acids, (**C**) Isobole curve for BE, DE, and AE green coffee beans and wholeemal wheat flour compounds, (**D**) Estimation of strength of interactions of buffer extractable (BE), bioaccessible (DE), and bioavailable (AE) green coffee beans and wholeemal wheat flour compounds and pure ferulic and chlorogenic acids. It should be emphasized that, although in all cases the activity of GCB flour extracts was higher, the differences were not stark, especially in the cases of potentially bioaccessible (DE) and bioavailable (AE) samples. This fact demonstrates the complexity of interactions with food matrix components, because the activity of AE was relatively high in both GCB and WF extracts. Additionally, the activity of pure chemicals was also comparable (Figure 1B). The potential of pure phenolic acids for lipid preservation is strongly documented in the different food systems. Ferulic acid has the ability to delay the lipid oxidation process through the decay of hydroperoxides [23]. Phenolic compounds such as caffe acid, tannic acid, ferulic acid, catechin, gallic acid, and so on, have proved to be efficient antioxidants in different fish model systems [7]. Phenolic compounds, depending on their mode of action, can show different antioxidative activities in different seafood systems [23]. [PERSON] and others [24] demonstrated that the overall order of antioxidant efficiency for hydroxycinnamic acids in chilled horse mackerel was caffe acid > ferulic acid = chlorogenic acid = o-cumaric acid. Among the pure phenolic compounds, caffe acid, tannic acid, and gallic acid have been used for retardation of hemoglobin (Hb)-mediated lipid oxidation in fish muscle. Caffeic acid inhibits Hb-mediated lipid oxidation by various mechanisms. It strongly inhibits per Hb-mediated lipid oxidation in washed cod mince during storage. Caffeic acid might bind with perch Hb, thus preventing its autoxidation. Caffeic acid and gallic acid are able to lower lipid oxidation of washed bighead carp mince induced by myoglobin or Hb throughout storage [7]. It must be taken into account that, in natural systems, phenolic compounds do not occur singly but in mixtures, which generally modulates their activity. Thus, we decided to analyze the activity of whole extracts from WF and GCB and determine their interactions in comparison with pure chemical standards. According to isobolographic analysis, active compounds derived from both raw materials acted synergistically. However, the strength of synergism differed significantly depending on the kind of extract. The highest level of synergism was found in the case of extracts after simulated digestion (CI = 0.54). The results were compared with those obtained for pure chemical standards. As expected, ferulic and chlorogenic acids were able to protect lipids against oxidation. Their activity was comparable (EC\({}_{50}\) about 67 \(\upmu\)g DW/mL) (Figure 1B). As presented, these compounds demonstrated a nearly additive interaction (CI value about 0.94) (Figure 1A,D). In the food science literature, chelating power is indicated as the main reason for LPO ability because iron-chelating capacity plays an important role in preventing lipid oxidation induced by Fe\({}^{2+}\)[10]. In the cited study, ferulic acid displayed greater antioxidant activity than caffeic acid but was less efficient in inhibiting the Fe\({}^{2+}\)-LO. This low-antioxidant efficiency of ferulic acid could be caused by the inability of ferulic acid to chelate Fe\({}^{2+}\) in the Fe\({}^{2+}\)-LO system. In our previous study, we confirmed the comparable chelating power of ferulic and chlorogenic acids [25]. Interestingly, their activity (63.06 and 54.15 \(\upmu\)g/mL, respectively) was similar to the LPO ability presented in this paper.