Objective: To study on the four flavone-C-glycosides which were vicenin-2

luteolin-6-C-glucopyranosyl-8-C-xylopyranoside

quercetin-6-C-glucopyranoside and dihydroquercetin-6-C-glucopyranoside by electrospray ionization tandem mass spectrometry (ESI-MSn). Method: The samples were analyzed by ESI-MSn under positive and negative ion models. Result: Under negative ion model

flavone-C-glycosides which had pentose substituent take place sugar bond cleavage and generate fragment ions (m/z 90 and 60)

these which had hexose substituent generate fragment ions (m/z 120 and 90) and these which had two sugar substituents successively generate fragment ions (m/z 120

90 and 60). Under positive ion model

flavone-C-glycosides take place dehydration

and these flavones which had pentose substituent take place sugar bond cleavage and generate fragment ions (m/z 60)

these which had hexose substituent generate fragment ions (m/z 120). Conclusion: The ESI-MSn methods for the identification of flavone-C-glycosides

especially which had two sugar substituents

were established.