Identification and quantification of polymethoxylated flavonoids in different Citrus species using UPLC-QTOF-MS/MS and HPLC-DAD

Many species from the genus Citrus (Rutaceae) are used in traditional medicine and contain the well-studied group of polymethoxylated flavonoids (PMFs). PMFs appear to have a broad spectrum of activities, including anti-inflammatory and chemopreventive activities. Consequently, they have big potential to be developed as therapeutic agents or dietary supplements [1]-[3].

The profile and yield of PMFs is different for each Citrus species. Seven different species were profiled using UPLC-QTOF-MS/MS. The generated data were analyzed using GNPS Molecular Networking [4]. At least 30 different PMFs were identified.

As the yield of PMFs is different for every Citrus species, a generally applicable HPLC-DAD method was developed and validated according to the ICH guidelines [5] to quantify the amount of nobiletin and the total amount of PMFs. A calibration model of the external standard nobiletin (1.51 - 150.90 µg/mL) showed a good linear response (R² > 0.999). The method displayed a good intermediate precision on time and concentration levels, for both nobiletin as the total amount of PMFs. The recovery of the method was 99.3% for nobiletin.

Analysis of the seven samples showed qualitative and quantitative differences in the composition of PMFs in the respective species. While C. limon contained the lowest amount of total PMFs, C. depressa contained the highest amount. Qualitative analysis revealed the most broad variety of different PMFs in C. depressa, as well as in C. reticulata and C. reticulata x C. sinensis. This makes them interesting sources of PMFs for future development of therapeutic agents or dietary supplements.

• References

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