Objective: To identify the components in Tanreqing and clarify the differences between Tanreqing capsule and Tanreqing injection in chemical compositions. Method: An HPLC-ESI-MS/MS method was established and separation was performed with acetonitrile and 0.1% formic acid as mobile phase for gradient elution. Mass spectrometric data were obtained in electrospray ionization (ESI) negative ion mode

and the chemical components were identified with quasi-molecular ions and secondary fragment ions. Result: Forty-one compounds including organic acids (7 compunds)

flavonoids (10 compounds)

iridoids (4 compunds)

lignans (3 compounds)

phenylethanoid glycosides (9 compounds)

bile acids (4 compounds) and 4 unknown components were detected in Tanreqing capsule by HPLC-ESI-MS/MS. Moreover

the chemical structures of 25 compounds were identified

and the chemical structures of 16 compounds (including 4 unknown components) were inferred by their fragmentation patterns. However

only twenty three compounds were found in Tanreqing injection with the losses of 18 chemical compositions including three isolates of suspensaside

sweroside

forsythoside B

isoforsythiaside A

forsythiaside A

rutin

two isolates of suspensaside A

hyperin

aldosecologanin

two isolates of pinoresinol-β-D-glucoside/epipinoresinol-4'-O-glucoside/matairesinol-4'-O-glucoside

phillyrin

baicalein

taurochenodeoxycholic acid (TCDCA) and one unknown compound derived from Scutellariae Radix extract. These differences in compositions between the two preparations may be caused by active carbon adsorption

high temperature sterilization

and blending system in aseptic production process and ultrafiltration technique in process control of Tanreqing injection product. Conclusion: The different chemical constituents in Tanreqing capsule and injection were characterized by the established HPLC-ESI-MS/MS method

which could provide the basis for the quality control of two preparations.