Study on the Extraction of Nervonic Acid from the Oil of Xanthoceras sorbifolium Bunge Seeds

Abstract

Seven fatty acids were detected by GC-MS in Xanthoceras sorbifolium Bunge seed oil extracted at different temperatures, including Palmitic acid C16:0, Stearic acid C18:0, Oleic acid C18:1, Eicosenoic acid C20:1, Docosenoic acid C22:1, Tetracosenoic acid C24:1, and Linoleic acid C18:2. The highest content of nervonic acid (NA) was found in Xanthoceras sorbifolium Bunge seed oil extracted at 70 °C. Three methods were selected to analyze the extraction rate of nervonic acid in Xanthoceras sorbifolium Bunge seed oil, including urea complexation, low-temperature solvent crystallization, and a combined treatment using these two methods. The final content of nervonic acid obtained was 14.07%, 19.66%, and 40.17%, respectively. The combined treatment method increased the purity of nervonic acid in Xanthoceras sorbifolium Bunge seed oil by 12.62 times. Meanwhile, thermogravimetric behavior analysis of samples extracted using different methods was conducted by thermogravimetric analyzer, which suggested that the thermal stability of the samples extracted by the combined treatment was enhanced. These results can provide a new process parameter and scientific basis for the extraction of NA. At the same time, FTIR and NMR were also used to characterize the combined extraction sample, and the structure of the samples was proved.

Keywords: Xanthoceras sorbifolium Bunge seed oil; fatty acid; nervonic acid; thermogravimetry.

Figure 1

Flow chart of nervonic acid extraction. (A: Unrefined oil sample; B: Refined oil sample; NA is nervonic acid.)

Figure 2

Single factor column chart of urea complexation. (A): Volume of ethanol is a variable; (B): Mass of urea is a variable; (C): Temperature is a variable; (D): Time is a variable. a–e indicated significant differences (p < 0.05).

Figure 3

Interaction and contour plots of two-factor on urea complexation. (A): 3D plot of temperature vs. ethanol; (B): 3D plot of temperature vs. urea; (C): 3D plot of ethanol vs. urea; (D): Contour plots of temperature vs. ethanol; (E): Contour plots of temperature vs. urea; (F): Contour plots of ethanol vs. urea. Red indicates high content.

Figure 4

GC-MS chromatogram depicts the results of Xanthoceras sorbifolium Bunge seed oil of unrefined (as control (A)) and combined treatment (B). NA is nervonic acid.

Figure 5

(A): Column stacking plot of fatty acid percentage for different purification methods. (B): Thermogravimetric analysis for different purification methods; UC: urea complexation method; LT: low-temperature solvent crystallization method; CT: combined treatment; Control: unpurified Xanthoceras sorbifolium Bunge seed oil.

Figure 6

FTIR and NMR spectra of combined treated sample. (A): FTIR spectrum; (B): ¹H−NMR spectrum; (C): ¹³C−NMR spectrum. The green line represents the peak area integral. The main line in the three graphs represents the peak of the spectrum.