Identification and characterization of the chemical components of Iris tectorum Maxim and evaluation of their NO inhibitory activity

Rationale: Iris tectorum Maxim is a traditional medicinal herb that is commonly utilized for treating inflammatory conditions. The present study investigated the fragmentation patterns of isoflavone glycosides and their qualitative analysis. In addition, lipopolysaccharide (LPS)-induced RAW264.7 macrophages were used to evaluat the anti-inflammatory properties of I. tectorum Maxim samples collected at different time points during the year.

Method: High-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (HPLC/Q-TOF-MS/MS) and HPLC-DAD were employed for the qualitative and quantitative analysis. The fragmentation patterns of these isoflavones were observed in negative electrospray ionization mode with collision-induced dissociation (CID). Their anti-inflammatory activity was assessed via nitric oxide (NO) production in LPS-treated RAW 264.7 macrophages.

Results: A total of 15 chemical components were observed and tentatively identified by HPLC/Q-TOF-MS. At low collision energy, the relative abundances of the aglycone radical anion Y₀ ^- , [Y₀ -H]^-• , [Y₀ -CH₃ ]^-• , and [Y₀ -H-CH₂ ]^-• were used for the structural characterization of tectoridin and tectorigenin-4'-O-β-D-glucoside. The radical ions [Y₀ -CH₃ ]^-• and [Y₀ -H-2CH₃ ]^-• were also employed to differentiate between iristectorin A and iristectorin B based upon their high energy CID spectra. Levels of 9.02 mg/g of tectoridin and 1.04 mg/g of tectorigenin were found in samples collected in June, which exhibited 69.7% NO inhibitory activity.

Conclusion: The characteristic fragmentation patterns enabled us to reliably identify isoflavone glycosides. The results of the quantitative determination and NO inhibitory activity offer insight into the optimal I. tectorum Maxim harvesting time.