Abstract
It is usually a tedious task to profile the chemical composition of a given herbal medicine (HM) using high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) due to the time-consuming sample preparation and laborious post-acquisition data processing procedures. Even worse, some labile compounds may face degradation risks when exposed to organic solvents for a relatively long period. As one of the most popular HMs, the promising therapeutic benefits of Epimedii Herba (Chinese name: Yinyanghuo) are well defined; however, the chemical profile, and in particular those flavonoids that have been claimed to be responsible for the efficacy, remains largely unknown. Attempts are devoted here to achieve direct LC–MS measurement and efficient post-acquisition data processing, and chemome comparison among three original sources of Epimedii Herba, such as Epimedium sagittatum (Esa), E. pubescens (Epu), and E. koreanum (Eko) was employed to illustrate the strategy utility. A home-made online liquid extraction (OLE) module was introduced at the front of the analytical column to comprehensively transfer the compounds from raw materials onto the LC–MS instrument. A mass defect filtering approach was programmed to efficiently mine the massive LC–MS dataset after which a miniature database was built involving all chemical information of flavonoids from the genus Epimedium to draw a pentagonal frame to rapidly capture potential quasi-molecular ions (mainly [M–H]−). A total of 99 flavonoids (66 in Esa, 84 in Eko, and 66 in Epu) were captured, and structurally annotated by summarizing the mass fragmentation pathways from the mass spectrometric data of authentic compounds and an in-house data library as well. Noteworthily, neutral loss of 144 Da was firstly assigned to the neutral cleavage of rhamnosyl residues. Significant species-differences didn’t occur among their chemical patterns. The current study proposed a robust strategy enabling rapid chemical profiling of, but not limited to, HMs.
Highlights
A given herbal medicine (HM) is usually recognized as a complicated compound pool, resulting in a dramatic technical challenge for in-depth chemical profiling, even for a single chemical plant family-focused characterization [1,2,3,4]
Epimedii Herba was employed as a proof-of-concept example to illustrate the utility of online liquid extraction (OLE)-LC–MS complemented by the mass defect filtering (MDF) approach
Mass Defect Properties of Flavonoids A pentagonal frame was employed for mass defect filtering (MDF), and the frame was constructed by tightly following the descriptions in the literature [15]
Summary
A given herbal medicine (HM) is usually recognized as a complicated compound pool, resulting in a dramatic technical challenge for in-depth chemical profiling, even for a single chemical plant family-focused characterization [1,2,3,4]. A smart online liquid extraction (OLE) module has been configured allowing direct analysis of solid matrices, where aqueous acetonitrile and even water, are usually employed as the extraction solvents because the pressurized warm solvent exhibits lower viscosity and polarity and is able to efficiently extract less polar compounds [8,9,10,11,12,13,14] The hyphenation of this OLE module with conventional LC–MS might offer the desired opportunity for direct analysis of HMs. Accompanying the quick development of MS equipment, the resulting datasets are becoming more and more complicated, resulting in labor- and time-intensive data processing tasks. Epimedii Herba was employed as a proof-of-concept example to illustrate the utility of OLE-LC–MS complemented by the MDF approach
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