Comparative quantitative analysis of fruit oil from Hippophae rhamnoides (seabuckthorn) by qNMR, FTIR and GC–MS

Objective

To develop a qNMR method for quantitative analysis of triacylglycerols in fruit oil of Hippophae rhamnoides (seabuckthorn, SBT) and analyze commercial samples of SBT oils using GC–MS and FTIR.

Methods

SBT fruit oil (IPHRFH) was extracted with hexane and the triglyceride (TAG) was isolated by vacuum liquid chromatography. Six different branded SBT oils purchased from e-commerce suppliers (Amazon) and in-house prepared SBT oil was analyzed by qNMR and fatty acyl composition of TAGs determined by using NMR. In-house oil was also analysed by GC–MS and FTIR spectroscopy.

Results

The qNMR results showed that the oil contained 80.3% of triacylglycerol (TAG). The SBT oil TAGs comprised of linolenate 6.6%, palmitoleate/oleate 65.4%, and total saturated fatty acyl chain including palmitate 28% as determined by qNMR. GC–MS analysis revealed that the major acyl functionalities present in the TAG were palmitoleic acid 36.5%, oleic acid 12.9%, palmitic acid 21.2%, and linoleic acid 18%. Of the six commercial samples analyzed, samples from only one supplier (SW) were fruit oil; All others were the seed oils or mix of fruit oil and seed oil. The labels for samples except for the SW did not indicate whether it was fruit oil or seed oil.

Conclusion

The results suggest that SBT oil should be analyzed by combination of GC–MS, FTIR and qNMR for factual content of free fatty acid or TAGs, which are chemically different in nature and affect the quality of oil. GC–MS showed the content of omega free fatty acids after hydrolysis, while qNMR and FTIR showed the content of TAGs. The major acyl functionalities found in SBT fruit oil TAGs are palmitoleate/palmitate/oleate, while linoleate and linonelate make up a minor fraction. Furthermore, analysis of commercial samples showed discrepancies between label claims and actual content.