{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T10:48:00Z","timestamp":1772016480797,"version":"3.50.1"},"reference-count":43,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2022,1,17]],"date-time":"2022-01-17T00:00:00Z","timestamp":1642377600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Wilhelm-Doerenkamp Foundation","award":["NATVANTAGE Grant 2018"],"award-info":[{"award-number":["NATVANTAGE Grant 2018"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Metabolites"],"abstract":"<jats:p>Arnica tincture is a herbal medicinal preparation with anti-inflammatory activity which is used traditionally for the topical treatment of blunt injuries as well as rheumatic muscle and joint complaints. Its main bioactive constituents are sesquiterpene lactones (STLs) of the helenalin and 11\u03b1,13-dihydrohelenalin types. Besides the mentioned activity, the tincture and its isolated STLs have antileishmanial activity. In a recent in vivo study, a treatment with Arnica tincture cured cutaneous Leishmaniasis (CL) in a golden hamster model. CL is a neglected tropical disease affecting more than two million people every year, for which new treatments are urgently needed. In order to use Arnica tincture on open CL lesions of human patients, it is important to know how the constituents are metabolized. Therefore, in vitro metabolism experiments with liver microsomes of different species (rat, pig and human) were performed with the Arnica STLs helenalin acetate and 11\u03b1,13-dihydrohelenalin acetate. Phase I and phase II metabolism experiments were performed, as well as a combination of both. Glutathione conjugation plays a major role in the metabolism of these STLs, as could be expected based on previous reports on their reactivity. Besides glutathione conjugates, several other metabolites were formed, e.g., water conjugates and hydroxides. Our results show for the first time a detailed picture of the metabolism of Arnica STLs. The fast and extensive formation of glutathione conjugates makes it unlikely that low absorbed levels of these compounds, as expected after dermal absorption from Arnica tincture, could be of toxicological concern.<\/jats:p>","DOI":"10.3390\/metabo12010088","type":"journal-article","created":{"date-parts":[[2022,1,17]],"date-time":"2022-01-17T20:46:03Z","timestamp":1642452363000},"page":"88","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["In Vitro Metabolism of Helenalin Acetate and 11\u03b1,13-Dihydrohelenalin Acetate: Natural Sesquiterpene Lactones from Arnica"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4980-6227","authenticated-orcid":false,"given":"Franziska M.","family":"J\u00fcrgens","sequence":"first","affiliation":[{"name":"Institute of Pharmaceutical Biology and Phytochemistry, University of M\u00fcnster, Corrensstrasse 48, D-48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matthias","family":"Behrens","sequence":"additional","affiliation":[{"name":"Institute of Food Chemistry, University of M\u00fcnster, Corrensstra\u00dfe 45, D-48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3296-3058","authenticated-orcid":false,"given":"Hans-Ulrich","family":"Humpf","sequence":"additional","affiliation":[{"name":"Institute of Food Chemistry, University of M\u00fcnster, Corrensstra\u00dfe 45, D-48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2752-4931","authenticated-orcid":false,"given":"Sara M.","family":"Robledo","sequence":"additional","affiliation":[{"name":"PECET-School of Medicine, University of Antioquia, Calle 70 N\u00b0 52-21, Medellin 0500100, Colombia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2634-9705","authenticated-orcid":false,"given":"Thomas J.","family":"Schmidt","sequence":"additional","affiliation":[{"name":"Institute of Pharmaceutical Biology and Phytochemistry, University of M\u00fcnster, Corrensstrasse 48, D-48149 M\u00fcnster, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"588","DOI":"10.3855\/jidc.6833","article-title":"Recent updates and perspectives on leishmaniasis","volume":"9","author":"Savoia","year":"2015","journal-title":"J. Infect. Dev. Ctries."},{"key":"ref_2","unstructured":"(2020, April 15). Leishmaniasis. Available online: https:\/\/www.who.int\/news-room\/fact-sheets\/detail\/leishmaniasis."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Tamiru, H.F., Mashalla, Y.J., Mohammed, R., and Tshweneagae, G.T. (2019). Cutaneous leishmaniasis a neglected tropical disease: Community knowledge, attitude and practices in an endemic area, Northwest Ethiopia. BMC Infect. Dis., 19.","DOI":"10.1186\/s12879-019-4506-1"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1093\/qjmed\/hct116","article-title":"Leishmaniasis: Clinical syndromes and treatment","volume":"107","author":"McGwire","year":"2014","journal-title":"QJM Int. J. Med."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Azim, M., Khan, S.A., Ullah, S., Ullah, S., and Anjum, S.I. (2021). Therapeutic advances in the topical treatment of cutaneous leishmaniasis: A review. PLoS Negl. Trop. Dis., 15.","DOI":"10.1371\/journal.pntd.0009099"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2062","DOI":"10.3390\/molecules14062062","article-title":"Quantitative Structure\u2014Antiprotozoal Activity Relationships of Sesquiterpene Lactones","volume":"14","author":"Schmidt","year":"2009","journal-title":"Molecules"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"14118","DOI":"10.3390\/molecules200814118","article-title":"Search for Antiprotozoal Activity in Herbal Medicinal Preparations; New Natural Leads against Neglected Tropical Diseases","volume":"20","author":"Kaiser","year":"2015","journal-title":"Molecules"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Robledo, S.M., V\u00e9lez, I.D., and Schmidt, T.J. (2018). Arnica Tincture Cures Cutaneous Leishmaniasis in Golden Hamsters. Molecules, 23.","DOI":"10.3390\/molecules23010150"},{"key":"ref_9","unstructured":"European Directorate for the Quality of Medicines & HealthCare (EDQM) (2020). Arnicae flos. European Pharmacopoeia, Council of Europe. [10th ed.]."},{"key":"ref_10","unstructured":"European Medicines Agency (EMA) (2021, November 09). Assessment Report on Arnica montana L., Flos. Available online: https:\/\/www.ema.europa.eu\/en\/medicines\/herbal\/arnicae-flos."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"660","DOI":"10.1055\/s-0029-1185362","article-title":"Sesquiterpene Lactones in Arnica montana: Helenalin and Dihydrohelenalin Chemotypes in Spain","volume":"75","author":"Perry","year":"2009","journal-title":"Planta Med."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"678","DOI":"10.1055\/s-2000-8635","article-title":"On the Stability of Sesquiterpene Lactones in the Officinal Arnica Tincture of the German Pharmacopoeia1","volume":"66","author":"Schmidt","year":"2000","journal-title":"Planta Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1111\/j.1096-0031.2008.00244.x","article-title":"Secondary chemistry and ribosomal DNA data congruencies in Arnica (Asteraceae)","volume":"25","author":"Wagner","year":"2009","journal-title":"Cladistics"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Tosun, F., Beutler, J.A., Ransom, T.T., and Miski, M. (2019). Anatolicin, a Highly Potent and Selective Cytotoxic Sesquiterpene Coumarin from the Root Extract of Heptaptera anatolica. Molecules, 24.","DOI":"10.3390\/molecules24061153"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"6622894","DOI":"10.1155\/2021\/6622894","article-title":"Antiprotozoal Compounds from Urolepis hecatantha (Asteraceae)","volume":"2021","author":"Elso","year":"2021","journal-title":"Evid.-Based Complementary Altern. Med."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2849","DOI":"10.1016\/S0968-0896(99)00234-5","article-title":"Helenanolide type sesquiterpene lactones. Part 5: The role of glutathione addition under physiological conditions","volume":"7","author":"Schmidt","year":"1999","journal-title":"Bioorg. Med. Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"103","DOI":"10.5507\/bp.2010.017","article-title":"Phase II drug metabolizing enzymes","volume":"154","author":"Jancova","year":"2010","journal-title":"Biomed. Pap."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"106","DOI":"10.1055\/s-2000-11123","article-title":"Glutathione Adducts of Helenalin and 11\u03b1,13-Dihydrohelenalin Acetate Inhibit Glutathione S-Transferase from Horse Liver","volume":"66","author":"Schmidt","year":"2000","journal-title":"Planta Med."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1055\/s-2000-8566","article-title":"Effect of Sesquiterpene Lactones on Antioxidant Enzymes and Some Drug-Metabolizing Enzymes in Rat Liver and Kidney","volume":"66","author":"Murias","year":"2000","journal-title":"Planta Med."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3913","DOI":"10.1016\/0006-2952(89)90668-0","article-title":"In vitro inhibition of mouse hepatic mixed-function oxidase enzymes by helenalin and alantolactone","volume":"38","author":"Chapman","year":"1989","journal-title":"Biochem. Pharmacol."},{"key":"ref_21","first-page":"577","article-title":"Toxic Activities of Sesquiterpene Lactones: Structural and Biochemical Aspects","volume":"3","author":"Schmidt","year":"1999","journal-title":"Curr. Org. Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1167","DOI":"10.1211\/jpp.58.9.0002","article-title":"Permeation of bioactive constituents from Arnica montana preparations through human skin in-vitro","volume":"58","author":"Tekko","year":"2006","journal-title":"J. Pharm. Pharmacol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1016\/j.bcp.2013.09.007","article-title":"Pharmacokinetics","volume":"87","author":"Fan","year":"2014","journal-title":"Biochem. Pharmacol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1699","DOI":"10.1007\/s12010-009-8689-6","article-title":"Role of Human Liver Microsomes in In Vitro Metabolism of Drugs\u2014A Review","volume":"160","author":"Asha","year":"2010","journal-title":"Appl. Biochem. Biotechnol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1252","DOI":"10.1038\/nprot.2009.122","article-title":"Chromatographic assays of drug oxidation by human cytochrome P450 3A4","volume":"4","author":"Sohl","year":"2009","journal-title":"Nat. Protoc."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1002\/qua.560480709","article-title":"Electrostatic properties of glutathione: A quantum molecular study","volume":"48","author":"Broch","year":"1993","journal-title":"Int. J. Quantum Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"309","DOI":"10.4103\/0974-8490.188873","article-title":"Effects of Curcuma xanthorrhiza extracts and their constituents on phase II drug-metabolizing enzymes activity","volume":"8","author":"Salleh","year":"2016","journal-title":"Pharmacogn. Res."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"645","DOI":"10.1016\/S0968-0896(97)00003-5","article-title":"Helenanolide-type sesquiterpene lactones\u2014III. Rates and stereochemistry in the reaction of helenalin and related helenanolides with sulfhydryl containing biomolecules","volume":"5","author":"Schmidt","year":"1997","journal-title":"Bioorg. Med. Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"933","DOI":"10.1126\/science.1193478","article-title":"Cytochrome P450 Compound I: Capture, Characterization, and C-H Bond Activation Kinetics","volume":"330","author":"Rittle","year":"2010","journal-title":"Science"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"932","DOI":"10.1021\/cr9002193","article-title":"Hydrocarbon Hydroxylation by Cytochrome P450 Enzymes","volume":"110","year":"2010","journal-title":"Chem. Rev."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"7697","DOI":"10.1002\/ejoc.201301230","article-title":"On the Michael Addition of Water to \u03b1,\u03b2-Unsaturated Ketones Using Amino Acids","volume":"2013","author":"Resch","year":"2013","journal-title":"Eur. J. Org. Chem."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"6868","DOI":"10.1021\/jo400258w","article-title":"Mechanisms of Lactone Hydrolysis in Neutral and Alkaline Conditions","volume":"78","author":"Calle","year":"2013","journal-title":"J. Org. Chem."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"250","DOI":"10.1016\/j.jchromb.2016.08.034","article-title":"Identification of in vitro and in vivo metabolites of alantolactone by UPLC-TOF-MS\/MS","volume":"1033\u20131034","author":"Yao","year":"2016","journal-title":"J. Chromatogr. B"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2189","DOI":"10.1016\/S0968-0896(01)00131-6","article-title":"The influence of glutathione and cysteine levels on the cytotoxicity of helenanolide type sesquiterpene lactones against KB cells","volume":"9","author":"Heilmann","year":"2001","journal-title":"Bioorg. Med. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1080\/135475098231101","article-title":"Mercapturic acids as biomarkers of exposure to electrophilic chemicals:applications to environmental and industrial chemicals","volume":"3","author":"Commandeur","year":"1998","journal-title":"Biomarkers"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1325","DOI":"10.1002\/bmc.3167","article-title":"Study on the pharmacokinetics and metabolism of costunolide and dehydrocostus lactone in rats by HPLC-UV and UPLC-Q-TOF\/MS","volume":"28","author":"Peng","year":"2014","journal-title":"Biomed. Chromatogr."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"370","DOI":"10.1016\/j.jchromb.2017.11.039","article-title":"Metabolism and pharmacokinetics of alantolactone and isoalantolactone in rats: Thiol conjugation as a potential metabolic pathway","volume":"1072","author":"Zhou","year":"2018","journal-title":"J. Chromatogr. B"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1080\/03602532.2020.1853151","article-title":"What dominates the changeable pharmacokinetics of natural sesquiterpene lactones and diterpene lactones: A review focusing on absorption and metabolism","volume":"53","author":"Yu","year":"2021","journal-title":"Drug Metab. Rev."},{"key":"ref_39","unstructured":"Lake, B.G. (1987). Preparation and Characterization of Microsomal Fractions for Studies on Xenobiotic Metabolism, IRL Press."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/0003-2697(76)90527-3","article-title":"A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding","volume":"72","author":"Bradford","year":"1976","journal-title":"Anal. Biochem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1060","DOI":"10.1016\/j.jnutbio.2009.09.001","article-title":"In vitro and in vivo conjugation of dietary hydroxycinnamic acids by UDP-glucuronosyltransferases and sulfotransferases in humans","volume":"21","author":"Wong","year":"2010","journal-title":"J. Nutr. Biochem."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1846","DOI":"10.1016\/j.fct.2007.03.018","article-title":"Synthesis and characterization of deoxynivalenol glucuronide: Its comparative immunotoxicity with deoxynivalenol","volume":"45","author":"Wu","year":"2007","journal-title":"Food Chem. Toxicol."},{"key":"ref_43","unstructured":"European Medicines Agency (EMA) (2021, November 09). ICH Guideline M3(R2) on Non-Clinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorisation for Pharmaceuticals. Available online: https:\/\/www.ema.europa.eu\/en\/ich-m3-r2-non-clinical-safety-studies-conduct-human-clinical-trials-pharmaceuticals."}],"container-title":["Metabolites"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2218-1989\/12\/1\/88\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:02:57Z","timestamp":1760133777000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2218-1989\/12\/1\/88"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,1,17]]},"references-count":43,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2022,1]]}},"alternative-id":["metabo12010088"],"URL":"https:\/\/doi.org\/10.3390\/metabo12010088","relation":{},"ISSN":["2218-1989"],"issn-type":[{"value":"2218-1989","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,1,17]]}}}