Qualitative and quantitative analysis of polycyclic polyprenylated acylphloroglucinols from Garcinia species using ultra performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Polycyclic polyprenylated acylphloroglucinols (PPAPs) are a group of natural products isolated from different Garcinia species with a wide range of important biological activities. In this study, an ultra performance liquid chromatography (UPLC) coupled to photodiode-array detection and quadrupole time-of-flight mass spectrometry (Q-TOF) method was developed to characterize 16 PPAPs in 10 Garcinia species. In source dissociation techniques based on cone voltage fragmentation were used to fragment the deprotonated molecules and multiple mass spectrometry (MS/MS) using ramping collision energy were used to further break down the resulting product ions. The resulting characteristic fragment ions were generated by cleavage of C1-C5 bond and C7-C8 bond through concerted pericyclic reaction, which is especially valuable for differentiating three types of PPAPs isomers. As such, two new PPAPs isomers present in minor amount in the extracts of Garcinia oblongifolia were tentatively characterized by comparing their tandem mass spectra to the known ones. In addition, an UPLC-Q-TOF-MS method was validated for the quantitative determination of PPAPs. The method exhibited limits of detection from 2.7 to 21.4 ng mL⁻¹ and intra-day and inter-day variations were less than 3.7% and the recovery was in the range of 89-107% with RSD less than 9.0%. This UPLC-Q-TOF-MS method has successfully been applied to quantify 16 PPAPs in 32 samples of 10 Garcinia species, which were found to be a rich source of PPAPs.