Profiling the chlorogenic acids of Rudbeckia hirta, Helianthus tuberosus, Carlina acaulis and Symphyotrichum novae-angliae leaves by LC-MS(n).

BACKGROUND

Chlorogenic acids (CGAs) are a family of esters formed between quinic acid and certain cinnamic acids, most commonly caffeic, p-coumaric and ferulic acid. They show a variety of biological activities like antioxidant, anti-inflammatory, anti-HIV, anti-HBV and inhibition of mutagenesis and carcinogenesis, and are considered to be beneficial to human health. We have selected well-established plants of Asteraceae family and these are used in folk medicines as antivirals.

OBJECTIVE

Investigating the CGA profile of anti-viral herbal remedies, we aim at identifying selected chlorogenic acids commonly encountered in these plants in order to identify suitable candidates for anti-viral screening. It should be noted that neuroaminidase inhibitors, recently introduced into the clinical practice as Tamiflu or Relenza, bear a remarkable structural similarity to CGAs, suggesting potentially a similar mode of action.

METHODS

Methanolic extracts were used for LC-MS analysis. The LC equipment with DAD detector was interfaced with a high-resolution MicroTOF mass spectrometer for molecular formula assignment and an ion trap mass spectrometer for assignment of CGA regiochemistry based on characteristic fragmentation patterns. For the identification of cis cinnamoylquinic acids, extracts were treated with UV-irradiation.

RESULTS

A series of CGAs were identified by their tandem mass spectra and retention times. We also found that diacyl CGAs containing cis isomer of cinnamic acids have the same tandem MS spectra as those containing the trans isomer.

CONCLUSIONS

In this study, all the CGAs present in the leaves of Rudbeckia hirta, Helianthus tuberosus, Carlina acaulis and Symphyotrichum novae-angliae were identified qualitatively to their regioisomeric level without any purification or isolation, and assignment was based on their LC-MS(n) behaviour and the change in the intensity after the UV-irradiation. A series of CGAs common to these anti-viral herbal remedies was identified, which will in the future be selected for further detailed biological screening.