Identification and characterization of the chemical components of Iris tectorum Maxim. and evaluation of their nitric oxide inhibitory activity.

Rationale: Iris tectorum Maxim. is a traditional medicinal herb that is commonly used to treat 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 evaluate the anti-inflammatory properties of I. tectorum Maxim. samples collected at different time points during the year.

Methods: High-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (HPLC/QTOF-MS/MS) and HPLC with diode-array detection were employed for qualitative and quantitative analysis. The fragmentation patterns of the 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 RAW264.7 macrophages.

Results: A total of 15 chemical components were observed and tentatively identified using HPLC/QTOF-MS/MS. At low collision energy, the relative abundances of the aglycone radical anions Y , [Y  - H] , [Y  - CH ] and [Y  - H- CH ] were used for the structural characterization of tectoridin and tectorigenin-4'-O-β-D-glucoside. The radical ions [Y  - CH ] and [Y  - H - 2CH ] 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.

Conclusions: 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.