Structural and quantitative analysis of Equisetum alkaloids

Area of Science:

• Phytochemistry
• Analytical Chemistry
• Toxicology

Background:

• Equisetum palustre (marsh horsetail) is recognized for its toxicity to livestock.
• Previous research identified two main alkaloids: palustrine and N(5)-formylpalustrine.
• A need existed for comprehensive analysis of all alkaloids and their distribution.

Purpose of the Study:

• To develop and apply a method for identifying and quantifying Equisetum alkaloids.
• To characterize newly discovered alkaloids.
• To determine the distribution and variability of these alkaloids in E. palustre.

Main Methods:

• Development of a High-Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry (HPLC-ESI-MS/MS) method.
• Simple sample preparation techniques were employed.
• Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry were used for structural elucidation.

Main Results:

• A total of eight Equisetum alkaloids were detected in most plant samples.
• Three new alkaloids were identified: palustridiene, N(5)-Acetylpalustrine, and N(5)-formylpalustridiene.
• Alkaloid content varied widely (88–597 mg/kg dry weight) across plant organs, origins, and seasons.
• Palustrine and palustridiene were consistently the major alkaloids.

Conclusions:

• A robust HPLC-ESI-MS/MS method enables comprehensive analysis of Equisetum alkaloids.
• Significant variability in alkaloid profiles necessitates careful consideration of E. palustre toxicity.
• Palustrine and palustridiene are key compounds in understanding the plant's toxicological impact.