Metabolomic characterization of a pomegranate (Punica granatum L.) water extract by LC-QTOF-MS

Introduction

Pomegranate (Punica granatum L.) is a fruit widely grown in the Mediterranean region and is widely recognized for its high content of natural antioxidants, including hydrolysable tannins, flavonoids, and phenolic acids. The present study focuses on the detailed metabolomic profiling of a pomegranate water extract using liquid chromatography.

Methods and materials

The metabolomic profile was determined using Ultra-high performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (HPLC-QTOF-MS) in negative mode.

Results and Discussion

LC-MS/MS analysis revealed a complex polyphenolic profile dominated by hydrolysable tannins, mainly ellagitannin- and gallotannin-derived compounds. Low-molecular-weight constituents included gallic acid (m/z 169.0149; MS/MS 125.0252), succinic acid (m/z 117.0195; MS/MS 73.0294), and glutaric acid (m/z 131.0724; MS/MS 85.0664).

The high-mass fraction was characterized by multiple tannins, including digalloylglucose isomers (m/z 483.0795), galloyl-HHDP-hexosides (m/z 633.0751/633.0733; MS/MS m/z 301, 463), trigalloylglucose isomers (m/z 635.0852; MS/MS 483, 465, 301), punicalagins α/β (m/z 541.0288; MS/MS 301, 275, 249), valoneic acid dilactone derivatives (m/z 425.0176), granatin A (m/z 799.0645), and galloyl-bis-HHDP-glucoside (m/z 935.0802), all showing fragmentation patterns consistent with sequential loss of galloyl and Hexahydroxydiphenoyl (HHDP) groups.

Simple flavonoids were also detected, including epicatechin (m/z 289.0729), catechin (m/z 289.0732), quercetin (m/z 301.0373; MS/MS 179, 151), and cyanidin-3-O-glucoside (m/z 449.1118; MS/MS 287.0586), along with derivatives such as 3,3′-di-O-methyl ellagic acid (m/z 329.0322) and methyl-quercetin sulfate (m/z 395.0071; MS/MS 301).

Overall, the MS/MS data confirmed that the sample is highly enriched in ellagitannin and gallotannin-type polyphenols, characterized by characteristic fragment ions at m/z 301 (ellagic acid) and m/z 169/125 (galloyl units), together with flavan-3-ols and flavonols, supporting fingerprint.

Conclusions

LC-MS/MS analysis showed a polyphenol-rich extract dominated by ellagitannins and gallotannins, supported by characteristic MS/MS fragments (m/z 301 and 169/125), with minor contributions from flavonoids.