Analysis of triptophenolide and its related compounds from Tripterygium wilfordii Hook.f by electrospray ionization tandem mass spectrometry

Triptophenolide and its related compounds from Tripterygium wilfordii Hook.f is a kind of diterpenoids which shows anti-inflammatory activity. To study the metabolites of triptophenolide related compounds, the fragmentation mechanisms of them were investigated by using negative electrospray tandem mass spectrometry. With the aid of high resolution of ESI–QTOF–MS/MS, the fragmentation mechanisms of six diterpenoid compounds were systematically investigated. The fragmentation behavior mainly depends on what substituent groups the benzyl C ring bears. If there is a hydroxyl group on the position of C14, loss of CH4 is dominating. However, the successive loss of two CH3 radicals is predominant when the hydroxyl group of O14 is methylated. The lactone ring is prone to be dissociated to loss of CO, CO2 and C2H2O2 molecules. The pericyclic reaction can occur on A ring if there is an active hydrogen resides on C ring. Furthermore, one metabolite of compound A1 was confirmed by cytochrome P450 in vitro and the structure was proposed by tandem mass experiment together with the fragmentation mechanisms of this type of compounds.