Evaluation of Tissue-Specific Plant MetabolitesUsing Probe Electrospray Ionization Kit and LC-MS

Significance of the Topic

Plants produce a vast array of metabolites that localize in specific tissues, influencing color, taste, and functionality. Rapid, site-specific profiling of these compounds enhances insights into plant physiology, supports food quality assurance, and advances metabolomics research.

Objectives and Study Overview

This study evaluates a workflow combining probe electrospray ionization (PESI) and quadrupole time-of-flight (QTOF) LC-MS to map metabolites in microregions of strawberry and sansho fruits. The aim is to demonstrate intuitive sampling, high mass accuracy, and elimination of chromatographic separation for high-throughput analysis.

Methodology and Instrumentation

• Sampling procedure:
  • Solid-needle probe contacts target tissue for one second with 10 µL of 50 % isopropanol–water solvent.
  • Targets include colored and non-colored strawberry receptacle and achenes, and sansho secretory cavities and nearby pericarp.
• Instrumentation:
  • Probe Electrospray Ionization Kit DPiMS QT
  • Shimadzu LCMS-9030 QTOF mass spectrometer
• Analytical conditions:
  • Positive ion mode; Data-Dependent Acquisition (DDA)
  • DL temp 250 °C; Heat block 50 °C; Interface voltage 3.5 kV
  • MS range m/z 50–1000; MS/MS range m/z 10–1000 for strawberry and m/z 10–300 for sansho
  • Measurement time: 0.1 min (strawberry), 1.0 min (sansho)
• Data analysis: LabSolutions Insight Explore with online ChemSpider database search and composition estimation.

Main Results and Discussion

• Strawberry fruit:
  • Receptacle tissues contained hexoses, disaccharides, and citric acid regardless of coloration.
  • Colored receptacle exhibited pelargonidin-3-hexoside; achenes showed cyanidin-3-glucoside and pelargonidin-3-hexoside, confirming tissue-specific anthocyanin distribution (mass error ≤0.32 mDa).
• Sansho fruit:
  • Secretory cavities were rich in sanshool and hydroxy-sanshool.
  • Pericarp near cavities showed minor hydroxy-sanshool signals, indicating predominant accumulation in secretory structures (mass error ≤0.59 mDa).

Benefits and Practical Applications

• Elimination of chromatographic steps accelerates analysis and reduces sample prep.
• High-throughput capability with seconds-per-sample sampling time.
• Site-specific metabolic profiling aids breeding, quality control in food and beverage industries, and plant science investigations.

Future Trends and Possibilities

• Optimizing solvent compositions to enhance ionization of diverse metabolite classes.
• Coupling with imaging techniques for guided sub-millimeter sampling.
• Extending the approach to additional plant species and tissues to create comprehensive metabolite distribution maps.
• Automating sampling and data processing using robotics and advanced software pipelines.

Conclusion

Probe electrospray ionization paired with QTOF LC-MS provides a rapid, accurate, and minimally invasive method for mapping tissue-specific plant metabolites. The workflow delivers high mass accuracy, simplifies sample preparation, and enables high-throughput analysis, positioning it as a versatile tool for plant research, food quality assessment, and industrial analytics.

Reference

1. Hiraoka K, Nishidate K, Mori K, Asakawa D, Suzuki S. Development of probe electrospray using a solid needle. Rapid Commun Mass Spectrom. 2007;21:3139–3144.
2. Ishibashi M, Zaitsu K, Yoshikawa I, Otagaki S, Matsumoto S, Oikawa A, Shiratake K. Tissue-specific anthocyanin localization in strawberry revealed by PESI-MS. Hort Res. 2023;10:uhad039.
3. Luo J, Hou X, Li S, Luo Q, Wu H, Shen G, Gu X, Mo X, Zhang Z. Identification of sanshool compounds in sansho fruit by mass spectrometry. Food Chem X. 2022;14:100342.