## 1 Introduction
It is found in large amounts in coffee (Coffea robusta), cocoa seeds, chokeberry and blueberry fruits, mulberry fruit and leaves, and herbal spices [6] as well as in elderberry flowers. It belongs to a group of strong antioxidants. It increases the sensitivity of cells to insulin, probably reduces the risk of diabetes and has choleretic properties [8]. Chlorogenic acid is mainly known for its anticarcinogenic, antioxidant and anti-inflammatory properties [9]. Many epidemiologic studies have also focused on chlorogenic  
Figure 1: Structures of hydroxycinnamic acids and chlorogenic acid [6]. acid in the context of its health benefits [10; 11]. It has been proposed to have benefits in obesity [12], type 2 diabetes (T2 DM) [13], stroke [14] and Alzheimer's disease [15] and on endothelial function as well as blood pressure [16; 17]. Another study revealed the adverse effects of CGA, including headache, diarrhea and complications in higher doses for a person with a sensitive stomach [18]. However, no comprehensive investigation has been conducted regarding the side effects of chlorogenic acid. Chlorogenic acid, as mentioned, plays an important role in the prevention of cancer. Experiments conducted on animals proved the high level of effectiveness of chlorogenic acid as a means of protecting liver cells against poisoning with carbon tetrachloride and cobalt and cadmium isotopes [19]. In the same study, it was shown that caffeic, chlorogenic, ferulic, ellagic and gallic acids have the ability to block carcinogenic compounds formed by metabolic transformations of some carcinogenic substances, e.g., 4-nitroquinoline-1-oxides. According to other authors [20], chlorogenic, caloric, caffeic and cynarin acids can be used as agents against skin damage caused by UV-A and UV-B radiation, which is the result of an action preventing collagen degradation. It is worth considering that in such a complex system as the various biologically active compounds present in the plant (herbal) raw material, it is not possible to clearly indicate a substance with a specific effect (at a specific concentration) without taking into account other substances present in various quantities. Of course, this also applies to the extraction methods and their efficiency in relation to the individual components. For example, in studies [21] in which only the concentrations of two acids, caffeic and chlorogenic acid, were taken into account, it was found that at the level of \(2.8\times 10^{-4}\) mol/dm\({}^{3}\) they showed similar antioxidant activities, while the use of acids with concentrations above \(10\times 10^{-4}\) mol/dm\({}^{3}\) showed a higher antioxidant efficiency of caffeic acid than chlorogenic acid during the oxidation of triacylglycerols in sunflower oil. A similar dependence of the higher antioxidant efficiency of caffeic acid compared to chlorogenic acid was confirmed by other researchers in relation to sunflower oil [22] and corn oil [23]. A more detailed explanation of the mechanisms related to the antioxidant properties of selected phenolic acids can be found in a paper by [PERSON] [6]. The above examples indicate that the biological activities of raw plant materials depend on many factors (the raw material, environmental factors, mutual quantitative relationships of individual chemical compounds, epigenetic reactions of plants to stressors, etc. ), and therefore a very strict and precise determination of all the health-promoting properties of plants is very difficult, if not impossible, at the moment. Nevertheless, an attempt to build mathematical models based on a smaller amount of input data may be justified, as they gives an opportunity to select narrowed technological ranges during the processing of herbal raw material in order to obtain the optimal amount of the selected biologically active substance (in terms of the efficiency or energy consumption of the process).