Insight Into the Secondary Metabolites of Geum Urbanum L. and Geum Rivale L
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plants Article Insight into the Secondary Metabolites of Geum urbanum L. and Geum rivale L. Seeds (Rosaceae) Marek Bunse 1,2, Peter Lorenz 1 , Florian C. Stintzing 1 and Dietmar R. Kammerer 1,* 1 Department of Analytical Development & Research, Section Phytochemical Research, WALA Heilmittel GmbH, Dorfstr. 1, DE-73087 Bad Boll/Eckwälden, Germany; [email protected] (M.B.); [email protected] (P.L.); [email protected] (F.C.S.) 2 Department of Plant Systems Biology, Hohenheim University, Garbenstraße 30, DE-70599 Stuttgart, Germany * Correspondence: [email protected] Abstract: The present study aimed at the identification and quantitation of phenolic compounds, fatty acids, and further characteristic substances in the seeds of Geum urbanum L. and Geum rivale L. For this purpose, individual components of extracts recovered with MeOH, CH2Cl2, and by cold- pressing, respectively, were characterized by HPLC-DAD/ESI-MSn and GC/MS and compared with reference compounds. For both Geum species, phenolic compounds, such as flavonoids and gallic acid derivatives, and triterpenes, such as saponins and their aglycones, were detected. Surprisingly, both Geum species revealed the presence of derivatives of the triterpenoid aglycons asiatic acid and madecassic acid, which were characterized for the first time in the genus Geum. Furthermore, the fatty acids of both species were characterized by GC–MS after derivatization. Both species showed a promising fatty-acid profile in terms of nutritional properties because of high proportions of unsat- urated fatty acids. Linoleic acid and linolenic acid were most abundant, among other compounds Citation: Bunse, M.; Lorenz, P.; such as palmitic acid and stearic acid. In summary, the present study demonstrates the seeds of Stintzing, F.C.; Kammerer, D.R. G. urbanum and G. rivale to be a valuable source of unsaturated fatty acids and bioactive phenolics, Insight into the Secondary which might be exploited for nutritional and cosmetic products and for phytotherapeutic purposes. Metabolites of Geum urbanum L. and Geum rivale L. Seeds (Rosaceae). Keywords: avens; seeds; specialty oils; phenolics; triterpenes; asiatic acid; fatty acids; γ-linolenic Plants 2021, 10, 1219. https:// acid; RP-HPLC-DAD/ESI-MSn; GC/MS doi.org/10.3390/plants10061219 Academic Editors: Laura Grat,iela Vicas, and Mariana Eugenia Mures, an 1. Introduction Geum L., commonly called avens, is a genus in the Rosaceae family, subfamily Received: 20 May 2021 Rosoideae, which comprises about 55 species of rhizome forming perennial herbaceous Accepted: 9 June 2021 plants. The genus Geum is widespread across Eurasia, North and South America, and Published: 15 June 2021 Africa. Avens species are found in exposed vegetation and forests and sometimes also as “weeds”. The species G. montanum L. (alpine avens), G. reptans L. (creeping avens), Publisher’s Note: MDPI stays neutral G. urbanum L. (wood avens), and G. rivale L. (water avens) are found as part of the Central with regard to jurisdictional claims in published maps and institutional affil- European flora. G. urbanum and G. rivale are among the best-known European species, iations. which are also used in pharmaceutical applications, especially in complementary medicine such as phytotherapy. For this purpose, mainly the roots and rhizomes (in the following text summarized as roots), but also aerial parts of the two species are processed. G. urbanum and G. rivale have long been used in traditional European medicine for the treatment of diarrhea, stomach complaints, febrile diseases, gingivitis, and inflammation of mucous Copyright: © 2021 by the authors. membranes [1]. In addition, the roots of wood avens and water avens have been used as a Licensee MDPI, Basel, Switzerland. substitute for clove because of their eugenol content, as an additive to spirits and liqueurs This article is an open access article distributed under the terms and in the food industry, and as cosmetic ingredients of toothpastes and mouthwashes [1]. conditions of the Creative Commons The main secondary metabolites of the roots and herbal parts reported so far are gallo- Attribution (CC BY) license (https:// and ellagitannins, procyanidins and other polyphenolics, ascorbic acid, and essential oil creativecommons.org/licenses/by/ components, such as eugenol [2]. The high tannin content is typical for the Rosaceae 4.0/). family. More recent studies, especially on G. urbanum, have reported anti-inflammatory, Plants 2021, 10, 1219. https://doi.org/10.3390/plants10061219 https://www.mdpi.com/journal/plants Plants 2021, 10, x FOR PEER REVIEW 2 of 17 and essential oil components, such as eugenol [2]. The high tannin content is typical for the Rosaceae family. More recent studies, especially on G. urbanum, have reported anti- Plants 2021, 10, 1219 2 of 17 inflammatory, antimicrobial, antioxidant, neuroprotective, and hypotensive effects [2]. It is, therefore, surprising that the phenolic compound and fatty-acid profiles of the seeds of these two species have neither been studied nor used for pharmaceutical, nutritional, or antimicrobial,culinary purposes. antioxidant, Therefore, neuroprotective, this study ai andmed hypotensiveat a profound effects characterization [2]. It is, therefore, of the surprisingsecondary thatmetabolite the phenolic profile compound of the seeds and of G. fatty-acid urbanum profilesand G. rivale of the, focusing seeds of particularly these two specieson phenolic have neithercompounds, been studiedsuch as normonophenol used for pharmaceutical,structures and ellagitannins, nutritional, or as culinary well as purposes.triterpenes Therefore, and their thisderivatives. study aimed Furthermor at a profounde, the fatty-acid characterization profile was of the analyzed secondary and metabolitecompared profilebetween of the the two seeds Geum of G. species. urbanum In andaddition,G. rivale two, focusing extraction particularly methods, i.e., on pheno-solvent licextraction compounds, and cold-pressing, such as monophenol should structuresbe assessed and with ellagitannins, regard to seed as welloil yields as triterpenes and their andcompound their derivatives. profiles. Although Furthermore, Geum is the known fatty-acid to be profilerich in phenolics, was analyzed and extracts and compared derived betweentherefrom the exert two Geumvariousspecies. pharmaceutical In addition, activities two extraction to treat methods, several diseases, i.e., solvent there extraction is still a andlack cold-pressing, of comprehensive should knowledge be assessed concerni with regardng the to seedphytochemical oil yields and composition their compound of the profiles.seeds. The Although latter Geumare expectedis known to to be be potentia rich in phenolics,l sources andof secondary extracts derived metabolites, therefrom thus exertrendering various them pharmaceutical promising candidates activities to for treat applications several diseases, in the there food, is cosmetic, still a lack and of comprehensive knowledge concerning the phytochemical composition of the seeds. The pharmaceutical sectors. latter are expected to be potential sources of secondary metabolites, thus rendering them promising2. Results candidatesand Discussion for applications in the food, cosmetic, and pharmaceutical sectors. 2.2.1. Results GC/MS and Analyses Discussion of Fatty Acids 2.1. GC/MSThe diaspores Analyses (fruit) of Fatty of Acids G. urbanum and G. rivale (Figure 1) are randomly spread by animals.The diasporesFor this reason, (fruit) they of G. have urbanum someand morphologicG. rivale (Figure adaptations1) are randomlysuch as spikes, spread hooks, by animals.barbed projections, For this reason, or theyawns have [3]. someFurthermore, morphologic seeds adaptations store proteins, such as carbohydrates, spikes, hooks, barbedphosphates, projections, and lipids or awns that [3 ].act Furthermore, as the carbon seeds skeleton store proteins, and energy carbohydrates, source, e.g., phos- for phates,germination and lipids [4]. To that analyze act as the the carbon fatty-acid skeleton compositions, and energy seeds source, were e.g., defatted for germination with CH [24Cl].2 Toor analyzecold-pressed, the fatty-acid and compositions,the oils obtained seeds were defattedanalyzed with by CH chromatographic2Cl2 or cold-pressed, and andspectrometric the oils obtained methods. were analyzed by chromatographic and spectrometric methods. FigureFigure 1.1. SeedsSeeds of of GeumGeum urbanum urbanum L.L. (A ()A and) and GeumGeum rivale rivale L. (L.B) (withB) with their their typical typical morphologic morphologic adaptations (spikes, hooks, or barbed projections ()). The scale bar shown corresponds to 1 mm. adaptations (spikes, hooks, or barbed projections (I). The scale bar shown corresponds to 1 mm. TheThe fatty-acidfatty-acid compositioncomposition ofof thethe twotwo speciesspecies revealedrevealed thethe presencepresence ofof palmiticpalmitic acid,acid, linoleiclinoleic acid, acid,α α-linolenic-linolenic acid, acid, and and stearic stearic acid acid as as major major components, components, which which were were assigned assigned onon thethe basisbasis ofof their their mass mass spectra spectra and and a a comparison comparison with with those those of of reference reference compounds compounds andand withwith thethe NIST NIST database.database. TheThe relativerelative proportionsproportions ofof individualindividual fattyfatty acidsacids (Figure(Figure2 )2) ofof thethe two two species species were were almost almost identical identical for for palmitic