nt of the m/z 271 ion. The spectrum (Figure 6) is an exact match of the spectrum generated by the MS/MS experiment of apiginin (Figure 7). Compound X is a flavonoid! In fact, it is the flavonoid rhoifolin (apiginin 7-0-neohesperidoside).


Figure 7. Comparison of full-scan MS/MS (271) spectrum of apiginin with the full-scan MS4 (579>433>271>) mass spectrum of Compound X.

Conclusions

Electrospray ionization of an unknown compound provides a soft ionization technique allowing the generation of an intact pseudomolecular ion at m/z 579. The MS² experiment yielded two major ions which were indicative of the loss of a deoxyhexose sugar (m/z 433) and a product mass which was the same as a base component of flavonoids (m/z 271). MS³ of the m/z 433 ion proved that the m/z 271 ion was a product of the m/z 433 ion and also indicated the loss of a hexose sugar. The MS⁴ experiment on the m/z 271 ion resulted in a fragmentation spectrum which was a direct match with the fragment spectrum of apiginin. The direct match indicates that the unknown compound belongs to the flavonoid class.





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