Multidirectional Analysis of Plant Alkaloids Using MS Imaging (MSI) and Oxygen Attachment Dissociation (OAD

Significance of the Topic

Plant alkaloids are bioactive nitrogen-containing compounds with key roles in defense mechanisms and pharmaceutical applications. Their spatial distribution within plant tissues and detailed structural information are critical for drug discovery, agricultural research, and understanding plant metabolism.

Objectives and Study Overview

This study presents a multidirectional workflow combining mass spectrometry imaging (MSI) with collision-induced dissociation (CID) and oxygen attachment dissociation (OAD) to map and elucidate the structures of alkaloids in potato sprouts. The goals were to visualize the localization of glycoalkaloids and to achieve confident structural assignments of isomeric and analog compounds.

Methodology and Instrumentation

Potato sprouts were sectioned and coated with α-cyano-4-hydroxycinnamic acid (CHCA) using a uniform 0.7 µm layer. MSI experiments employed an iMScope QT system with 10–25 µm spatial resolution. Two MS/MS techniques were applied:

• CID-MS/MS on a Q-TOF instrument at collision energies of 10 V and 80 V.
• OAD-MS/MS using atomic oxygen radicals generated from water vapor in a quartz tube OAD source.

Data acquisition and in silico fragment prediction used IMAGEREVEAL MS and LabSolutions Insight Explore software.

Key Results and Discussion

MSI revealed that solanine (m/z 868.508) and chaconine (m/z 852.513) accumulate predominantly in potato sprout tissues. CID spectra alone produced multiple candidate structures for each precursor. Incorporation of OAD-induced fragment ions, such as the diagnostic m/z 150.128 peak, allowed unambiguous assignment of glycoalkaloid formulas (C10H16N) and elimination of alternative isomers. The complementary dissociation patterns of OAD enhanced confidence in structural elucidation beyond conventional CID.

Benefits and Practical Applications

The integrated MSI-CID-OAD workflow enables:

• Spatial mapping of bioactive alkaloids at cellular resolution.
• Discrimination of structural isomers through unique radical-induced cleavage.
• Streamlined identification of known and novel alkaloids for pharmacological screening.

Future Trends and Potential Applications

Future developments may include coupling OAD with high-throughput imaging platforms and expanding radical chemistries to target other functional groups. Integration with machine learning–driven in silico libraries could further accelerate discovery of trace alkaloids in diverse plant systems.

Conclusion

The presented approach successfully combines MSI with CID and OAD to both localize and structurally characterize plant alkaloids. OAD provides unique fragment ions that resolve isomeric ambiguity, enhancing the reliability of alkaloid profiling. This multidirectional strategy holds promise for advanced metabolite discovery and targeted analysis in plant science and pharmaceutical research.