## 4 Discussion
In the analysed milk thistle and borage oils, the content of sterols was measured at 347.52 mg\(\cdot\)kg\({}^{-1}\) oil and 261.33 mg\(\cdot\)100 g\({}^{-1}\) oil, respectively. The results were similar to those published by other authors [71], who estimated the general content of sterols in vegetable oils as 338.46-340.37 mg\(\cdot\)100 g\({}^{-1}\) oil. In a study on different cultivars of milk thistle, [PERSON] and [PERSON] [49] described the level of \(\beta\)-sitosterol in seed oil as ranging from 617.9 to 689.4 mg\(\cdot\)100 g\({}^{-1}\) oil and for \(\Delta^{7}\)-sterol from 386.5 to 403.0 mg\(\cdot\)100 g\({}^{-1}\) oil. In a study on borage oil, [PERSON] et al. [72] demonstrated that the general content of sterols was 1098 mg\(\cdot\)100 g\({}^{-1}\) oil, while, in palm oil, it was 58 mg\(\cdot\)100 g\({}^{-1}\) oil. Tocopherols are present in oils, in varying quantities, in four primary forms: \(\alpha\), \(\beta\), \(\gamma\), \(\delta\). Depending on the form, they show varying levels of antioxidative activity. Of all the tocochromanols, \(\alpha\)-tocopherol (vit. E) shows 100%, \(\beta\)-tocopherol 50%, and \(\gamma\)-tocopherol 25%. Scientific evidence suggests that the content of tocopherols and phenols varies depending on the process of oil extraction employed [73; 74]. [PERSON] and [PERSON] [73] observed that borage oil obtained through the process of cold pressing contained over 711 mg\(\cdot\)kg\({}^{-1}\) of tocopherol. In the cold-pressed borage seed oil analysed in the present study, the content of total tocopherol was 108 mg\(\cdot\)kg\({}^{-1}\), and in the milk thistle seed oil, it was 3541.45 mg\(\cdot\)kg\({}^{-1}\). [PERSON] and [PERSON] [74] analysed borage oil available on the market and reportedtocopherol content at the level of 1976 mg\(\cdot\)kg\({}^{-1}\). As for studies on milk thistle oils conducted by other researchers, the products tended to have higher content of \(\alpha\)-tocopherol as compared to other types of tocopherols (275.70 mg\(\cdot\)kg\({}^{-1}\)) [49]. As follows from the literature data, similar amounts of this ingredient are found in sunflower oil [8]. The remaining substances include carotenoids and chlorophylls--both responsible for the characteristic colour of oils. The content of carotenoid and chlorophyll pigments in all vegetable oils depends on the type and maturity of the raw material, as well as the technology used for the extraction and refinement of the oil [75]. Both chlorophylls and carotenoids serve important physiological functions in living plants. Chlorophylls are involved in photosynthesis, while carotenoids protect plants against oxidation. The content of the ingredients may vary depending on the particular type of oil and the method of its production (refined, not refined). As posited by [PERSON] et al. [76], the content of chlorophyll in oils can range from 25 mg\(\cdot\)kg\({}^{-1}\) in sesame oil to 3807 mg\(\cdot\)kg\({}^{-1}\) in unrefined hem oil. In refined oils, this ranges from 5 mg\(\cdot\)kg\({}^{-1}\) in rape oil to 58.5 mg\(\cdot\)kg\({}^{-1}\) in soybean oil. As for the content of carotenoids, in unrefined oils, it ranges from 30 mg\(\cdot\)kg\({}^{-1}\) in sesame seed oil to 3639 mg\(\cdot\)kg\({}^{-1}\) in pumpkin seed oil. In analyses conducted by [PERSON] et al. [77], some oils, including milk thistle oil, showed chlorophyll content higher than measured in the presently tested oil (2.68 mg\(\cdot\)kg\({}^{-1}\)), namely 4.82 mg\(\cdot\)kg\({}^{-1}\). In another study, [PERSON] et al. [78] demonstrated that weather and environmental conditions influenced the content of chlorophylls and carotenoids in borage oil. At 3.96 mg\(\cdot\)kg\({}^{-1}\), their result was comparable to our own. The literature provides very little data on the content of phytosterol oil. However, based on what is available, we know that phytosterols (plant sterols) are secondary components of vegetable oils and constitute a considerable portion of the non-saponifiable substances [49; 79].