Isolation, Method Development, and Validation of Diterpenes in Coffee Oil: Identification by Multiple Reaction Monitoring Approach with Atmospheric Pressure Chemical Ionization Mode

Objectives: The aim of the present study is to isolation, identification, and quantification of free diterpenes in coffee oil of Coffea arabica. Materials and Methods: For the isolation of free diterpenes, saponification reaction step was employed and followed with a liquid-liquid extraction procedure applied. Cafestol and kahweol were identified by multiple reaction monitoring (MRM) of positive ionization (MRM) mode of atmospheric pressure chemical ionization (APCI) mass spectrometry detection. The quantification of free diterpenes was done by high-performance liquid chromatography with diode array detector. The developed method was validated according to the international conference on harmonization guidelines. Results: The ion transitions of the precursor to the product ion at (M + H)⁺ m/z 317.20→146.90, 281.00, 299.00 for cafestol and 315.10→144.90, 278.90, 296.90 for kahweol were observed. The proposed method was validated for linearity with excellent correlation coefficient of cafestol and kahweol were found to be 0.9997 and 0.9996, respectively. The intra-day and intermediate precisions and repeatability showed the percentage relative standard deviation was <1%. The recovery rate for cafestol and kahweol were observed to be in the acceptable limit of 95.303%–98.539% and 95.963%–97.174%, respectively. The limit of detection of cafestol and kahweol were found to be 6.81 and 7.35 ppm, respectively. The limit of quantitation (LOQ) was found to be 22.72 and 24.52 ppm, respectively. Conclusion: The developed method is simple, rapid, precise, accurate and it is recommended for efficient assays in routine work.