Determination of perillaldehyde in perilla herbs based on relative molar sensitivity (RMS) using a combination of ¹H-quantitative NMR and HPLC/UV

¹H-quantitative NMR (¹H-qNMR) has become a powerful tool for producing absolutely pure reference standards (RSs) for HPLC. However, when the RS is unstable, the purity gradually declines before HPLC is performed and creates problems in generating reliable quantitative data. To address this, a method using a stable RS with relative molar sensitivity (RMS) to analyte has been reported [1]. In this study, we used a stable RS for the determination of the unstable compound perillaldehyde in perilla herbs, which is listed in the Japanese Pharmacopoeia (JP). We applied an off-line combination of ¹H-qNMR and HPLC/UV to estimate the RMS of the analyte (perillaldehyde) to the RS. Diphenyl sulfone (DS), an inexpensive and stable reagent with a high purity, was selected as the RS. The response ratio (Rr) of the analyte to the RS, obtained by HPLC/UV, was corrected using the molar ratio (Rn) obtained by ¹H-qNMR. The experiment was validated using the same sample in five NMR and seven HPLC instruments at five institutes. The average RMS (Rr/Rn) was 0.983 and the reproducibility relative standard deviation (RSD) was 1.027%. The perillaldehyde content of perilla herbs determined based on RMS was identical to that determined by the assay listed in JP. These results revealed that the quantitative assay for perillaldehyde in perilla herbs did not require an easily decomposable perillaldehyde reagent and that the method using the RMS of perillaldehyde to DS was thought to be acceptable to JP.

• References

• 1 Nishizaki Y, Sato-Masumoto N, Nakanishi A, Hashizume Y, Tandia M, Yamazaki T, Kuroe M, Numata M, Ihara T, Sugimoto N, Sato K. Determination of hesperidin and monoglucosylhesperidin contents in processed foods using relative molar sensitivity based on ¹H-quantitative NMR. Food Hyg Saf Sci 2018; 59: 1-10