Technical Approach for Structural Analysis of an Unknown Compound in Huoxiang Zhengqi Oral Liquid based on Linear Ion Trap Mass Spectrometry

Summary

Here, we show a standard protocol that combines multi-stage mass spectrometry trees with a fragmentation process based on Huoxiang Zhengqi oral liquid.

Abstract

Chinese herbal compounds (CHCs) play an irreplaceable role in Chinese medicine, and identifying their complex constituents has been a significant research focus in recent years. Huoxiang Zhengqi oral liquid is a classic Chinese patent medicine whose chemical composition requires further investigation at the molecular level. Traditional mass spectrometers, such as time-of-flight and Orbitrap, typically only provide secondary fragmentation information. Based on a linear ion trap mass spectrometer, compounds could be broken down more thoroughly, thereby obtaining deeper fragment information. This paper develops a structural exploration technique for unknown compounds in CHCs, encompassing sample pretreatment, ultra-performance liquid chromatography preparation, mass spectrometry preparation, full-spectrum testing, secondary mass spectrometry testing, multi-level mass spectrometry testing, and result analysis. Representative results demonstrate the derivation process of the compound structure. We discuss factors influencing the experimental technique, such as isomers, polyhydroxy compounds, and instrument resolution. Based on the derivation of the microscopic molecular structure of unknown compounds through multistage mass spectrometry fragmentation, the established experimental method is versatile and applicable for structural characterization of bioactive small molecules in traditional Chinese medicine and their linkage to pharmacological mechanisms.

Introduction

Chinese herbal compounds (CHCs), as invaluable assets of traditional Chinese medicine (TCM), have accrued millennia of validated clinical experience¹. They fulfill an irreplaceable role in disease prevention, therapeutic intervention, and rehabilitation². Through multi-herb synergism, CHCs treat the human body holistically, operationalizing the core tenets of holism and syndrome differentiation-based therapy³. Within contemporary medical frameworks, CHCs garner global recognition for their polypharmacological mechanisms engaging multi-target pathways⁴, with broad applicatio....

Protocol

1. Sample pretreatment

1. Open the packaging of the commercial HXZQ. Accurately transfer 0.1 mL of HXZQ into a 2 mL sample bottle, then add 0.9 mL of water. Shake the solution until it is thoroughly mixed.
2. Prepare an injection syringe (1 mL) and a microporous membrane filter (0.22 μm). Filter the solution into a new 2 mL sample bottle.
   NOTE: Take appropriate personal precautions during experimental procedures.

2. Ultra-performance liquid chromatography (UPLC) preparation

1. Double-click on the Xcalibur software. Click Ready to Download<....

Results

We suggested that all the m/z information needed to be collated first, and then the mass difference value between the parent ion and the fragment ion was calculated. Found the compound that was reported in the database or literature, and then deduced the unknown compound structure reversely based on this known structure.

All detected compounds and their corresponding fragment ions were presented by m/z values. A subset of these fragment ions could be matched to authenticated reference standard.......

Discussion

The combination of LIT-MS and its MSⁿ fragmentation technology provides a method for identifying unknown compounds in CHCs. Unlike traditional tandem MS modes in Orbitrap and Q-TOF MS, linear ion trap can specifically capture target ions, effectively avoiding interference from co-eluting ions²³. This method achieves molecular-level precision, providing relatively accurate chemical structural information, thereby partially addressing the challenge of qualifying unknown compounds due to d.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Acetonitrile	Thermo Scientific	CAS 75-05-8	Liquid state
Formic acid	Thermo Scientific	CAS 64-18-6	Liquid state
Huoxiang Zhengqi Oral Liquid	Chongqing Taiji Industry (Group) Co., Ltd.	State Drug Standard Code Z50020409	Object of study
Linear ion trap mass spectrometer	Thermo Scientific	LTQ XL	IT-MS instrument
liquid chromatograph	Thermo Scientific	U3000	UPLC instrument
Xcalibur	Thermo Scientific	version 2.0	UPLC-IT-MS operational software