Qualitative Analysis of Daphnane Diterpenoids in Various Parts of Daphne pontica L. by UHPLC-Q-Exactive-Orbitrap MS

Daphne pontica L. is an evergreen shrub that is recorded as an anti-diarrheic plant in Turkish folk medicine. Previous studies on D. pontica have reported, albeit slightly, the isolation of daphnane diterpenoids, but no systematic phytochemical analysis of daphnane diterpenoids has been conducted.

This study aimed to comprehensively investigate daphnane diterpenoids in the extracts from the different parts (stems, leaves, and fruits) of D. pontica.

An ultra-high-performance liquid chromatography coupled with Q-Exactive hybrid quadrupole Orbitrap mass spectrometer (UHPLC-Q-Exactive-Orbitrap MS) was used for the qualitative analysis of D. pontica. The stems, leaves, and fruits of D. pontica were extracted with diethyl ether. Each extract was then pretreated by a solid phase extraction cartridge and subjected to LC-MS/MS analysis. Detected daphnane diterpenoids were tentatively identified by comparison with an in-house daphnane library, and their chemical structures were estimated in detail by MS/MS fragmentation evaluation.

A total of 33 kinds of daphnanes were identified from the different parts of D. pontica, and were classified into three subtypes: daphnane orthoester, polyhydroxy daphnane, and macrocyclic daphnane orthoester. Among them, six daphnanes were postulated to be previously unreported compounds based on MS/MS fragmentation elucidation. Furthermore, the three plant parts showed similar daphnane diterpenoid profiles, with the stems containing the most abundant daphnane diterpenoids.

This is the first study to perform qualitative analysis of daphnane diterpenoids systematically and comprehensively in different parts of D. pontica. The results revealed that D. pontica is a plant resource rich in a variety of daphnane diterpenoids.