Comparative Analysis of Phytochemicals and Antioxidant Properties of Borage Oil (Borago officinalis L.) and Milk Thistle (Silybum marianum Gaertn)

There is currently a growing interest in oils characterised by specific medicinal, cosmetic, or dietary properties. For this reason, the seeds of two plants, milk thistle (Silybum marianum Gaertn) and borage (Borago officinalis L.), were studied by subjecting them to the process of cold pressing. The extracted oils were then examined in terms of their chemical composition and biological activity, and qualitatively analysed with the use of FTIR spectroscopy. The oils contained linoleic and octadecenoic acids in amounts of 47.84%, 35.31% (milk thistle oil) and 35.43%, 25.18% (borage oil). They were characterised by low water content, roughly 0.088% for thistle and 0.075% for borage, and simultaneously relatively high phosphorus content, reaching, respectively, 47.7 and 33.1 mg·kg−1. The mean peroxide value was 4.22 for milk thistle and 2.83 mmolO2·kg−1 for borage, and the acid number was 5.17 and 3.9 mgKOH·g−1, respectively. FTIR spectroscopy was used to conduct a qualitative analysis, which revealed slight discrepancies in intensity at 3005 cm−1, which confirmed differences in the content of fatty acids and oil pigments between the oils. The obtained results provided information on the applicability of the studied seeds and oils obtained therefrom as basic components of pharmaceutical and cosmetic products with potential health benefits.