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approximately 500 species, each of which contain apigenin/luteolin flavonoid derivatives (C-glycosylflavones), which frequently occur as isomers [7]. By characterising and identifying 8-C and 6-C glycoside critical isomer pair ratios of isoorientin/orientin, isovitexin/vitexin it’s possible to distinguish the four species of Passiflora:- P. edulis, alata, caerulea and incarnata [8]. The two 8-C and 6-C glycoside forms have distinctive isomeric positive ion and negative ion electrospray product ion spectra. However, utilising such specific characteristic analyte information in a data dependent or targeted analysis strategy can be hindered by sample complexity.
Figure 2. Structures of 6-C glycosides isoorientin/isovitexin and 8-C glycosides orientin/vitexin glycoside marker isomer pairs with positive and negative ion CCS values.
full spectra acquisition the quadrupole is operated in RF-only mode as a wide band- pass filter to transmit a wide mass range. The continuous ion beam is gated and pulsed into an orthogonal accelerator, where ions are accelerated down the flight tube and follow a focused path to the detector. In the mass analyser, lighter ions traverse faster than heavier ions and are resolved based on mass to charge ratio. In a Q-IM-oa-TOF-MS platform an ion mobility separation device is included between the quadrupole and the mass analyser (see Figure 1). Nowadays it is routine to detect thousands of components in a single analysis, which can be followed by retrospective targeted data analysis.
The commercial introduction of sub-2µm particles with systems operating at higher
back pressures and high mobile phase linear velocities, have facilitated a reduction in the length of chromatographic gradients, while retaining or increasing peak capacity, and affording improvements in sensitivity [5].
Despite these advances in LC and MS (including MS/MS), it can still be a challenge to confirm the presence of a specific analyte, especially when isomers/ structurally related compounds produce the same isomeric product ions and in the presence of co-extracted matrix components. One example is the identification of flavonoids in medicinal plants. Over 4,000 flavonoids have been identified, they are a widespread class of compounds possessing diverse pharmacological and biological properties [6]. The genus Passiflora contains
Efficacy regulation and assessment of over the counter (OTC) herbal medicines extends beyond phytochemical profiling. Quality control to establish purity and determine the presence of fumigants, pesticides, fungi, mycotoxins and bacteria (salmonella and E. coli) is required to ensure consumer safety. Analysis is required to optimise extraction procedures and the blending of extracts to produce a known quantity of active ingredients within a final product herbal formulation. Environmental conditions can also impact phytochemical make-up. Commodity stability and degradation relating to storage conditions, packaging and humidity need also to be assessed. Efficacy within controlled clinical trials requires standardised extracts and standardised doses. Here, we review advances in LC-MS analysis that can be used to overcome challenges in phytomedicine characterisation and facilitate profiling of phytochemical over-the-counter commodity products.
In this article, we offer insights into how the
Figure 3. I) Three-dimensional separation using UPLC-IM-MS (ACQUITY UPLC I Class and SYNAPT G2-Si) and II) HDMSE
and III) MSE
comparison.
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