Abstract
Aerial parts, leaves, and stems of Gaultheria procumbens are polyphenol-rich herbal medicines with anti-inflammatory and antioxidant effects. The present study focused on identifying active markers of the G. procumbens extracts in an integrated approach combining phytochemical and biological capacity tests. The target compounds, representing all classes of Gaultheria polyphenols, were pre-selected by LC-ESI-PDA-MS/MS. For unambiguous identification, the key analytes, including a rare procyanidin trimer (cinnamtannin B-1), miquelianin potassium salt, and two new natural products: quercetin and kaempferol 3-O-β-d-xylopyranosyl-(1→2)-β-d-glucuronopyranosides, were isolated by preparative HPLC and investigated by spectroscopy (HR-ESI-MS, UV-vis, CD, 1D- and 2D-NMR), thiolysis, flame photometry, optical rotation experiments, and absolute configuration studies. The significant contribution of the pre-selected compounds to the biological effects of the extracts was confirmed in vitro: the analytes significantly and in a dose-dependent manner down-regulated the pro-oxidant and pro-inflammatory functions of human neutrophils ex vivo (inhibited the release of reactive oxygen species, IL-1β, TNF-α, and neutrophils elastase, ELA-2), inhibited two key pro-inflammatory enzymes (cyclooxygenase, COX-2, and hyaluronidase), and most of them, except gaultherin, exerted potent direct antioxidant activity (ferric reducing antioxidant power and superoxide anion scavenging capacity). Moreover, cellular safety was confirmed for all compounds by flow cytometry. Eventually, as these mechanisms have been connected to the health benefits of G. procumbens, 11 polyphenols were accepted as active markers, and a simple, accurate, reproducible, and fully validated RP-HPLC-PDA method for standardisation of the target extracts was proposed.
Highlights
IntroductionThe most profitable strategy for selecting Quality control (QC) markers is based on the biological potency of the individual compounds and their contribution to the pharmacological effects of herbal products [3]
The LC-mass spectral (MS)/MS analysis, isolation, and spectroscopic experiments led to the selection and complete structural identification of eleven model compounds representing all classes of Gaultheria polyphenols, including one new natural product
The second new natural compound was identified among minor components of the plant
Summary
The most profitable strategy for selecting QC markers is based on the biological potency of the individual compounds and their contribution to the pharmacological effects of herbal products [3]. Two sets of analytical procedures are recommended for the QC process: chromatographic fingerprinting with mass spectral (MS) detection (for authentication purposes) 4.0/). Considering the molecular diversity of plant constituents, proper structural annotation of fingerprints is still challenging despite the advantages of multistage mass spectral (MSn ) profiling [6]. In the case of rare phytochemicals, especially glycosides, identification of their detailed structural features, such as the absolute configuration of sugar components, glycosylation position of polyhydroxylated aglycones or interglycosidic linkage in polyglycosides, requires their isolation from the plant material and the application of some additional analytical techniques including nuclear magnetic resonance (NMR)
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