Physicochemical characterization of Orychophragmus violaceus seeds and oil, a potential source of dihydroxy-fatty acids

Seed oils are an attractive feedstock for sourcing biobased materials. Oils containing hydroxy fatty acids (HFAs) are of particular interest due to their unique properties and chemical utility. Orychophragmus violaceus (Ov) contains two unique dihydroxy fatty acids, making it a potential source of HFAs. In this study, we thoroughly investigated the properties of Ov seeds and its oil. Ov seeds had a thousand seed weight of 3.1 g, bulk density of 591 g L⁻¹, and true density of 1144 g L⁻¹. The seeds had a high oil content of 42.2 wt% and crude protein and carbohydrate contents of 23.8 and 25.2 wt%, respectively. Different oil extraction methods were evaluated, and cold pressing followed by hexane extraction of the press cake yielded the highest amount of HFAs. The Ov oil contained 50.5 wt% of diunsaturated HFA wuhanic acid and 9.9 wt% of monounsaturated nebraskanic acid. The thermal properties of Ov oil were sufficient for use in industrial applications, with a pour point of −18 °C and an oxidation onset of 182.8 °C. The T_d95 of the oil under nitrogen atmosphere was 314.2 °C. The oil exhibited superb lubricant properties as determined by high frequency reciprocating rig (HFRR), with lower average wear scars and coefficient of frictions when compared to the petroleum-based lubricant PAO-6. Analysis of the glucosinolate content of the defatted seed meal indicated that it contained a high epiprogoitrin content of 69.80 µM g⁻¹. Other relevant oil properties were measured and compared to castor and lesquerella oils, two other HFA-containing oils. The high oil content and advantageous properties of the seed oil make Ov a strong candidate for domestication as an industrial oil seed crop.