Hong-Yan Zou1, Jun Luo, De-Ran Xu, Ling-Yi Kong. 1. State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing, 210009, People's Republic of China.
Abstract
INTRODUCTION: 'Naoyanghua', composed of the flowers of Rhododendron molle G. Don, is a traditional Chinese medicine that is widely known for its toxicity. Grayanane-type diterpenoids are the main active ingredients in R. molle, as well as possibly their toxicity: they are, however, difficult to isolate and analyse using common chromatographic methods, due to their small amounts and absence of conjugated groups, such as phenyl and α, β-unsaturated ketone. OBJECTIVE: To establish a highly sensitive, selective and reliable method for the qualitative evaluation of trace diterpenoids in the flowers of R. molle by using tandem solid-phase extraction followed by high-performance liquid chromatography with electrospray ionisation quadrupole-time-of-flight mass spectrometry (HPLC-ESI/QTOF/MS/MS). METHODS: Tandem solid phase extraction (SPE) was undertaken using a polyamide cartridge and a C18E cartridge in succession to enrich the trace diterpenoids. HPLC-ESI/QTOF/MS/MS was used to determine the fragmentation patterns of diterpenoids and to tentatively characterise their fragmentation pathways. RESULTS: HPLC-ESI/QTOF/MS/MS detected a total of 14 diterpenoids, eight of which were identified by comparison with literature sources and six based on fragmentation analysis. Among the latter six, rhodojaponin VI-3-glucoside was tentatively identified as a new diterpenoid glycoside and rhodojaponin VII, rhodojaponin IV and rhodojaponin I were reported from R. molle for the first time. CONCLUSION: By qualitative research of diterpenoids in this plant by HPLC-ESI/QTOF/MS/MS, a reliable methodology for the analysis of these active constituents of R. molle was established for the first time.
INTRODUCTION: 'Naoyanghua', composed of the flowers of Rhododendron molle G. Don, is a traditional Chinese medicine that is widely known for its toxicity. Grayanane-type diterpenoids are the main active ingredients in R. molle, as well as possibly their toxicity: they are, however, difficult to isolate and analyse using common chromatographic methods, due to their small amounts and absence of conjugated groups, such as phenyl and α, β-unsaturated ketone. OBJECTIVE: To establish a highly sensitive, selective and reliable method for the qualitative evaluation of trace diterpenoids in the flowers of R. molle by using tandem solid-phase extraction followed by high-performance liquid chromatography with electrospray ionisation quadrupole-time-of-flight mass spectrometry (HPLC-ESI/QTOF/MS/MS). METHODS: Tandem solid phase extraction (SPE) was undertaken using a polyamide cartridge and a C18E cartridge in succession to enrich the trace diterpenoids. HPLC-ESI/QTOF/MS/MS was used to determine the fragmentation patterns of diterpenoids and to tentatively characterise their fragmentation pathways. RESULTS: HPLC-ESI/QTOF/MS/MS detected a total of 14 diterpenoids, eight of which were identified by comparison with literature sources and six based on fragmentation analysis. Among the latter six, rhodojaponin VI-3-glucoside was tentatively identified as a new diterpenoid glycoside and rhodojaponin VII, rhodojaponin IV and rhodojaponin I were reported from R. molle for the first time. CONCLUSION: By qualitative research of diterpenoids in this plant by HPLC-ESI/QTOF/MS/MS, a reliable methodology for the analysis of these active constituents of R. molle was established for the first time.