Phospholipid and n-alkane composition, anti-α-glucosidase and anti-cyclooxygenase activities of milk thistle oil

Abstract

Although milk thistle oil has been authorized as a new edible oil in many countries, there is a lack of information about its chemical and biological properties. Thus, this study aimed to characterize the phospholipid and n-alkane composition as well as the α-glucosidase and cyclooxygenase inhibitory effects of milk thistle oil. The phospholipid composition of milk thistle seed oil was determined by liquid chromatography coupled to mass spectrometry HPLC–ESI–MS method and five glycerophospholipid classes were detected: phosphatidylinositol (35.8 ± 2.31%), phosphatidylcholine (29.2 ± 1.43%), phosphatidylethanolamine (15.7 ± 1.75%), phosphatidylglycerol (12.4 ± 1.61%) and phosphatidic acid (6.9 ± 0.82%). Twenty-three phospholipid molecular species were characterized, containing mainly palmitic, oleic and linoleic acids. Using gas chromatography coupled to mass spectrometry, seventeen n-alkanes were detected ranging from C14 to C35 carbon atoms. Nonacosane (13.79 ± 1.15%) was the predominant compound followed by heptacosane (9.52 ± 0.87%) and hexacosane (9.33 ± 1.21%). The carbon preference index of long-chain n-alkanes (CPI25–35) exhibited mainly odd/even predominance. The phospholipid and n-alkane composition of milk thistle oil is quite different from that of other oilseeds, indicating the possible use of those compounds as a means of determining oil authenticity. The total phenolic content of the tested oil was 10.28 ± 1.2 mg GAE/ g of oil. Furthermore, the tested oil showed moderate anti-cyclooxygenase1 capacity (IC50 = 42.3 ± 0.8 μg/mL) in comparison with the positive control aspirin. However, the inhibitory effect of milk thistle oil against α-glucosidase (IC50 = 28.4 ± 0.54 μg/mL) was similar to that of the positive control acarbose, which reveals the tested oil as a promising source of natural α-glucosidase inhibitors, proves protection against type 2 diabetes. Milk thistle oil has an excellent potential for application in the food and pharmaceutical industries.