Extraction and Analyses of Flavonoids and Phenolic Acids from Canadian Goldenrod and Giant Goldenrod

Jure Zekič,Vesna Glavnik,Irena Vovk

doi:10.3390/f12010040

Abstract

Invasive alien plant species Canadian goldenrod (Solidago canadensis L.) and giant goldenrod (Solidago gigantea Aiton) were investigated as a source of phytochemicals and yellow dyes. Flavonoids and phenolic acids were extracted from the inflorescence of Canadian goldenrod with thirteen extraction solvents ethanol, methanol, acetone, water, and mixtures of organic solvents (70%, 80%, and 90%) with water. High performance thin-layer chromatography (HPTLC) coupled to densitometry and high-performance liquid chromatography with photo-diode array detector (HPLC-PDA) were used for analyses of the obtained sample test solutions (STSs), which showed the best and comparable extraction efficiencies for 70% acetone(aq), 70% methanol(aq), and 70% ethanol(aq). HPTLC combined with image analyses in fluorescent mode resulted in different chromatographic fingerprints for Canadian goldenrod and giant goldenrod STSs (70% acetone(aq)) after development, after post-chromatographic derivatization with NP reagent and after use of PEG reagent. The developed HPLC methods enabled analyses of phenolic acids and flavonoids (aglycones and glycosylated) in STSs and hydrolyzed STSs form inflorescence of Canadian and giant goldenrod. Different contents of chlorogenic acid, rutin, hyperoside, isoquercetin, and quercetin were observed in STSs of both goldenrod species. The analyses of hydrolyzed STSs confirmed that glycosylated flavonoids in Canadian and giant goldenrod inflorescence are mainly glycosides of quercetin, kaempferol, and isorhamnetin. Additional analyses using HPTLC and HPLC coupled to tandem mass spectrometry (MS/MS; HPTLC-MS/MS and LC-MS/MS) enabled tentative identification of phenolic acids and flavonoids (10 with HPTLC-MS/MS and 15 with LC-MS/MS), from which several were identified in Canadian (4 with HPTLC-MS/MS and 8 with LC-MS/MS) and in giant (7 with HPTLC-MS/MS and 9 with LC-MS/MS) goldenrod for the first time.

Highlights

Canadian goldenrod (Solidago canadensis L.) and giant goldenrod (Solidago giganteaAiton) are two highly variable plant species that belong to the genus Solidago and familyAsteraceae [1,2]
For both goldenrod species the use of 50% ethanol(aq) as the extraction solvent resulted in an almost two times higher extraction yield than the use of hexane
Using High performance thin-layer chromatography (HPTLC)-MS/MS method we tentatively identified two phenolic acids and six glycosylated flavonoids in Canadian and two phenolic acids and five glycosylated flavonoids in giant goldenrod

Summary

Introduction

Canadian goldenrod (Solidago canadensis L.) and giant goldenrod (Solidago giganteaAiton) are two highly variable plant species that belong to the genus Solidago and familyAsteraceae [1,2]. They are herbaceous perennial plants that originate from North America where they are found from Florida to Alaska in the US as well as in Canada [3] Both goldenrods are aggressive plants that thrive in ruderal habitats, meadows, pastures, fields, forests, on road sides, riversides, trenches, etc. Its presence in England originates from 1645 [3] Both Canadian and giant goldenrod were popular in botanical gardens and nurseries due to attractive looks with characteristic golden flowers and easy growth [3].

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