{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T18:24:09Z","timestamp":1787595849899,"version":"build-2736575974"},"reference-count":42,"publisher":"Public Library of Science (PLoS)","issue":"8","license":[{"start":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T00:00:00Z","timestamp":1787529600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Swiss Federal Office for Civil Protection, Spiez Laboratory","award":["353013581"],"award-info":[{"award-number":["353013581"]}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:p>\n                    The emergence of SARS-CoV-2 has intensified the search for novel antiviral agents, with plants representing a promising source due to the documented antiviral properties. Pheophorbides, chlorophyll breakdown products, have been demonstrated to impede viral entry of enveloped viruses. However, the frequent occurrence of pheophorbide A in plant extracts presents a challenge for antiviral screening, as it may obscure the discovery of novel antiviral compounds. The objective of this study was therefore leveling out the influence of pheophorbide A in an\n                    <jats:italic>in vitro<\/jats:italic>\n                    virus pretreatment assay, to prioritize extracts and fractions and support the identification of additional antiviral compounds in plant extracts. Using different experimental derived examples, the limitations and advantages of the strategy presented are discussed. Assay-derived protective effects were interpreted in relation to pheophorbide A quantification, allowing six out of 15 plant species to be prioritized for further investigations. Qualitative comparison of metabolite profiles of fractions with the extent of protective effect supported the prioritization process and led to the identification of candidate compounds potentially contributing to the observed protective effect in\n                    <jats:italic>Primula veris<\/jats:italic>\n                    L. beyond pheophorbide A. Overall, the results highlight the potential value of the proposed strategy for revealing bioactivity beyond known predominant effectors and suggest an applicability in natural product\u2013based screening approaches.\n                  <\/jats:p>","DOI":"10.1371\/journal.pone.0355466","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T17:30:33Z","timestamp":1787592633000},"page":"e0355466","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["A bioactivity-leveling approach for component-specific evaluation in natural product extracts: Optimizing SARS-CoV-2 antiviral screening by controlling for pheophorbide A"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8895-9416","authenticated-orcid":true,"given":"Corinna","family":"Urmann","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yvonne","family":"Gmach","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-1429-6865","authenticated-orcid":true,"given":"Niklas","family":"Hofer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nina","family":"Vahekeni","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonas","family":"Stehlin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yannick","family":"Geissmann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas","family":"Lardos","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Olivier","family":"Engler","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Evelyn","family":"Wolfram","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2026,8,24]]},"reference":[{"issue":"10","key":"pone.0355466.ref001","doi-asserted-by":"crossref","first-page":"659","DOI":"10.1055\/a-1177-4396","article-title":"Challenges at the time of COVID-19: opportunities and innovations in antivirals from nature","volume":"86","author":"A Hensel","year":"2020","journal-title":"Planta Med"},{"key":"pone.0355466.ref002","doi-asserted-by":"crossref","first-page":"109125","DOI":"10.1016\/j.cbi.2020.109125","article-title":"Plants derived therapeutic strategies targeting chronic respiratory diseases: chemical and immunological perspective","volume":"325","author":"P Prasher","year":"2020","journal-title":"Chem Biol Interact"},{"issue":"3","key":"pone.0355466.ref003","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1111\/lam.13637","article-title":"Antiviral plant-derived natural products to combat RNA viruses: targets throughout the viral life cycle","volume":"75","author":"L Owen","year":"2022","journal-title":"Lett Appl Microbiol"},{"issue":"20","key":"pone.0355466.ref004","doi-asserted-by":"crossref","first-page":"6197","DOI":"10.3390\/molecules26206197","article-title":"Plant-based natural products and extracts: potential source to develop new antiviral drug candidates","volume":"26","author":"E Thomas","year":"2021","journal-title":"Molecules"},{"key":"pone.0355466.ref005","unstructured":"Pubmed. National Library of Medicine (US), National Center for Biotechnology Information. http:\/\/www.ncbi.nlm.nih.gov\/pubmed"},{"key":"pone.0355466.ref006","first-page":"363","article-title":"Enveloped viruses","volume-title":"Advances in protein chemistry","author":"RJ Kuhn","year":"2003"},{"issue":"1","key":"pone.0355466.ref007","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.coviro.2012.12.004","article-title":"Uncoating of non-enveloped viruses","volume":"3","author":"M Suomalainen","year":"2013","journal-title":"Curr Opin Virol"},{"issue":"9267","key":"pone.0355466.ref008","doi-asserted-by":"crossref","first-page":"1513","DOI":"10.1016\/S0140-6736(00)04638-9","article-title":"Herpes simplex virus infections","volume":"357","author":"RJ Whitley","year":"2001","journal-title":"Lancet"},{"key":"pone.0355466.ref009","article-title":"The biology of influenza viruses","author":"NM Bouvier","year":"2008","journal-title":"Vaccine"},{"issue":"4","key":"pone.0355466.ref010","doi-asserted-by":"crossref","first-page":"396","DOI":"10.14789\/jmj.61.396","article-title":"An overview of ebola virus disease: history, pathogenesis, and treatment","volume":"61","author":"N Yamamoto","year":"2015","journal-title":"Juntendo Med Jl"},{"issue":"1","key":"pone.0355466.ref011","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1213\/ANE.0000000000004845","article-title":"Coronaviruses and SARS-CoV-2: a brief overview","volume":"131","author":"S Ludwig","year":"2020","journal-title":"Anesth Analg"},{"issue":"1","key":"pone.0355466.ref012","doi-asserted-by":"crossref","first-page":"41","DOI":"10.3390\/molecules28010041","article-title":"Antiviral activities of ethyl pheophorbides a and b isolated from aster pseudoglehnii against influenza viruses","volume":"28","author":"S Park","year":"2022","journal-title":"Molecules"},{"issue":"3","key":"pone.0355466.ref013","doi-asserted-by":"crossref","first-page":"557","DOI":"10.1016\/j.biotechadv.2017.12.016","article-title":"In vitro methods for testing antiviral drugs","volume":"36","author":"M Rumlov\u00e1","year":"2018","journal-title":"Biotechnol Adv"},{"key":"pone.0355466.ref014","doi-asserted-by":"crossref","first-page":"727","DOI":"10.3390\/molecules26030727","article-title":"COVID-19 prophylaxis efforts based on natural antiviral plant extracts and their compounds","volume":"26","author":"O Sytar","year":"2021","journal-title":"Molecules"},{"issue":"3","key":"pone.0355466.ref015","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1111\/1348-0421.12133","article-title":"Antiviral activity of extracts from Morinda citrifolia leaves and chlorophyll catabolites, pheophorbide a and pyropheophorbide a, against hepatitis C virus","volume":"58","author":"SL Ratnoglik","year":"2014","journal-title":"Microbiol Immunol"},{"issue":"10","key":"pone.0355466.ref016","doi-asserted-by":"crossref","first-page":"1048","DOI":"10.3390\/ph14101048","article-title":"SARS-CoV-2 fears green: the chlorophyll catabolite pheophorbide A is a potent antiviral","volume":"14","author":"GH Jimenez-Aleman","year":"2021","journal-title":"Pharmaceuticals (Basel)"},{"issue":"2","key":"pone.0355466.ref017","doi-asserted-by":"crossref","DOI":"10.1128\/AAC.01581-21","article-title":"A photoactivable natural product with broad antiviral activity against enveloped viruses, including highly pathogenic coronaviruses","volume":"66","author":"T Meunier","year":"2022","journal-title":"Antimicrob Agents Chemother"},{"issue":"10","key":"pone.0355466.ref018","doi-asserted-by":"crossref","first-page":"426","DOI":"10.1016\/S1360-1385(00)01735-0","article-title":"Degradation pathway(s) of chlorophyll: what has gene cloning revealed?","volume":"5","author":"K Takamiya","year":"2000","journal-title":"Trends in Plant Science"},{"key":"pone.0355466.ref019","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1055\/a-1955-4624","article-title":"Phyllobilins - bioactive natural products derived from chlorophyll - plant origins, structures, absorption spectra, and biomedical properties","volume":"89","author":"CA Karg","year":"2023","journal-title":"Planta Med"},{"issue":"3","key":"pone.0355466.ref020","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1105\/tpc.108.064089","article-title":"Pheophytin pheophorbide hydrolase (pheophytinase) is involved in chlorophyll breakdown during leaf senescence in Arabidopsis","volume":"21","author":"S Schelbert","year":"2009","journal-title":"Plant Cell"},{"issue":"3","key":"pone.0355466.ref021","doi-asserted-by":"crossref","first-page":"700","DOI":"10.1105\/tpc.109.210313","article-title":"A new chlorophyll degradation pathway","volume":"21","author":"NA Eckardt","year":"2009","journal-title":"Plant Cell"},{"key":"pone.0355466.ref022","doi-asserted-by":"crossref","first-page":"257","DOI":"10.3390\/md18050257","article-title":"Pheophorbide a: State of the Art","volume":"18","author":"A Saide","year":"2020","journal-title":"Mar Drugs"},{"key":"pone.0355466.ref023","doi-asserted-by":"crossref","first-page":"308","DOI":"10.3390\/md21050308","article-title":"Advanced methods for natural products discovery: bioactivity screening, dereplication, metabolomics profiling, genomic sequencing, databases and informatic tools, and structure elucidation","volume":"21","author":"SP Gaud\u00eancio","year":"2023","journal-title":"Mar Drugs"},{"key":"pone.0355466.ref024","doi-asserted-by":"crossref","first-page":"1731629","DOI":"10.3389\/fphar.2025.1731629","article-title":"Historical texts as a potential resource for plant-based antiviral agents against SARS-CoV-2: the example of the Receptarium of Burkhard III von Hallwyl from 16th-century Switzerland","volume":"16","author":"N Vahekeni","year":"2026","journal-title":"Front Pharmacol"},{"key":"pone.0355466.ref025","doi-asserted-by":"crossref","first-page":"104179","DOI":"10.1016\/j.phytol.2026.104179","article-title":"Shedding light on an active principle from the aerial parts of Echinacea purpurea against SARS-CoV-2 in vitro","volume":"74","author":"N Hofer","year":"2026","journal-title":"Phytochem Lett"},{"issue":"7","key":"pone.0355466.ref026","doi-asserted-by":"crossref","first-page":"893","DOI":"10.1039\/C9NP00068B","article-title":"Creating and screening natural product libraries","volume":"37","author":"BAP Wilson","year":"2020","journal-title":"Nat Prod Rep"},{"issue":"2","key":"pone.0355466.ref027","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1002\/pst.426","article-title":"Guidelines for accurate EC50\/IC50 estimation","volume":"10","author":"JL Sebaugh","year":"2011","journal-title":"Pharm Stat"},{"issue":"1","key":"pone.0355466.ref028","doi-asserted-by":"crossref","first-page":"1","DOI":"10.5812\/rijm.38369","article-title":"Anti-cancer activity of methanol extracts of cichorium intybus on human breast cancer SKBR3 cell line","volume":"5","author":"R Mehrandish","year":"2016","journal-title":"Razavi Int J Med"},{"issue":"1","key":"pone.0355466.ref029","doi-asserted-by":"crossref","first-page":"198","DOI":"10.3390\/molecules30010198","article-title":"Artemisinin stimulates neuronal cell viability and possess a neuroprotective effect in vitro","volume":"30","author":"SA Pukhov","year":"2025","journal-title":"Molecules"},{"issue":"10","key":"pone.0355466.ref030","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.3390\/ph16101491","article-title":"In vitro synergistic inhibitory effects of plant extract combinations on bacterial growth of methicillin-resistant Staphylococcus aureus","volume":"16","author":"J-Y Jeong","year":"2023","journal-title":"Pharmaceuticals (Basel)"},{"issue":"1","key":"pone.0355466.ref031","doi-asserted-by":"crossref","first-page":"2509657","DOI":"10.1080\/14756366.2025.2509657","article-title":"Chalcones inhibit firefly bioluminescence dependent on A and B-ring substitution pattern - a structure-activity study combined with molecular docking","volume":"40","author":"C Urmann","year":"2025","journal-title":"J Enzyme Inhib Med Chem"},{"issue":"12","key":"pone.0355466.ref032","doi-asserted-by":"crossref","first-page":"1513","DOI":"10.3390\/ph15121513","article-title":"In vitro anti-influenza virus activity of non-polar Primula veris subsp. veris Extract","volume":"15","author":"AG Eliopoulos","year":"2022","journal-title":"Pharmaceuticals"},{"issue":"1","key":"pone.0355466.ref033","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1039\/C4NP00085D","article-title":"Antiviral drug discovery: broad-spectrum drugs from nature","volume":"32","author":"JP Martinez","year":"2015","journal-title":"Nat Prod Rep"},{"issue":"4","key":"pone.0355466.ref034","doi-asserted-by":"crossref","first-page":"546","DOI":"10.1039\/c3np20094a","article-title":"Concepts and technologies for tracking bioactive compounds in natural product extracts: generation of libraries, and hyphenation of analytical processes with bioassays","volume":"30","author":"O Potterat","year":"2013","journal-title":"Nat Prod Rep"},{"issue":"11","key":"pone.0355466.ref035","doi-asserted-by":"crossref","first-page":"5035","DOI":"10.1021\/ac300698c","article-title":"XCMS Online: a web-based platform to process untargeted metabolomic data","volume":"84","author":"R Tautenhahn","year":"2012","journal-title":"Anal Chem"},{"key":"pone.0355466.ref036","doi-asserted-by":"crossref","DOI":"10.7554\/eLife.70780","article-title":"The LOTUS initiative for open knowledge management in natural products research","volume":"11","author":"A Rutz","year":"2022","journal-title":"Elife"},{"key":"pone.0355466.ref037","doi-asserted-by":"crossref","first-page":"113719","DOI":"10.1016\/j.phytochem.2023.113719","article-title":"Bisbibenzyls from Serbian Primula veris subsp. columnae (Ten.) L\u0215di and P. acaulis (L.) L","volume":"212","author":"M Novakovic","year":"2023","journal-title":"Phytochemistry"},{"issue":"9","key":"pone.0355466.ref038","doi-asserted-by":"crossref","first-page":"1033","DOI":"10.1016\/j.phytochem.2005.03.024","article-title":"Lipophilic flavones of Primula veris L. from field cultivation and in vitro cultures","volume":"66","author":"J Budzianowski","year":"2005","journal-title":"Phytochemistry"},{"issue":"12","key":"pone.0355466.ref039","doi-asserted-by":"crossref","first-page":"3137","DOI":"10.1002\/ptr.6781","article-title":"Naringenin, a flavanone with antiviral and anti-inflammatory effects: a promising treatment strategy against COVID-19","volume":"34","author":"H Tutunchi","year":"2020","journal-title":"Phytother Res"},{"issue":"12","key":"pone.0355466.ref040","doi-asserted-by":"crossref","DOI":"10.1177\/1934578X211066723","article-title":"Naringenin as a possible candidate against SARS-CoV-2 infection and in the pathogenesis of COVID-19","volume":"16","author":"PK Agrawal","year":"2021","journal-title":"Natural Product Commun"},{"key":"pone.0355466.ref041","doi-asserted-by":"crossref","first-page":"570919","DOI":"10.3389\/fimmu.2020.570919","article-title":"Perspective: the potential effects of naringenin in COVID-19","volume":"11","author":"RW Alberca","year":"2020","journal-title":"Front Immunol"},{"issue":"10","key":"pone.0355466.ref042","doi-asserted-by":"crossref","first-page":"2182","DOI":"10.1021\/jf404310y","article-title":"Antiviral activity of polymethoxylated flavones from \u201cGuangchenpi\u201d, the edible and medicinal pericarps of citrus reticulata \u2018Chachi\u2019","volume":"62","author":"J-J Xu","year":"2014","journal-title":"J Agric Food Chem"}],"container-title":["PLOS One"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0355466","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T17:30:43Z","timestamp":1787592643000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0355466"}},"subtitle":[],"editor":[{"given":"Armel Jackson","family":"Seukep","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2026,8,24]]},"references-count":42,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,8,24]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0355466","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,24]]}}}