{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:02:19Z","timestamp":1760234539981,"version":"build-2065373602"},"reference-count":33,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2021,5,31]],"date-time":"2021-05-31T00:00:00Z","timestamp":1622419200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT, ERDF, COMPETE, PORTUGAL2020","award":["UIDB\/04423\/2020, UIDP\/04423\/2020, PTDC\/SAU-PUB\/28736\/2017 (POCI-01-0145-FEDER-028736)"],"award-info":[{"award-number":["UIDB\/04423\/2020, UIDP\/04423\/2020, PTDC\/SAU-PUB\/28736\/2017 (POCI-01-0145-FEDER-028736)"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Thioxanthones are bioisosteres of the naturally occurring xanthones. They have been described for multiple activities, including antitumor. As such, the synthesis of a library of thioxanthones was pursued, but unexpectedly, four tetracyclic thioxanthenes with a quinazoline\u2013chromene scaffold were obtained. These compounds were studied for their human tumor cell growth inhibition activity, in the cell lines A375-C5, MCF-7 and NCI-H460. Photophysical studies were also performed. Two of the compounds displayed GI50 values below 10 \u00b5M for the three tested cell lines, and structure\u2013activity relationship studies were established. Three compounds presented similar wavelengths of absorption and emission, characteristic of dyes with a push-pull character. The structures of two compounds were elucidated by X-ray crystallography. Two tetracyclic thioxanthenes emerged as hit compounds. One of the two compounds accumulated intracellularly as a bright fluorescent dye in the green channel, as analyzed by both fluorescence microscopy and flow cytometry, making it a promising theranostic cancer drug candidate.<\/jats:p>","DOI":"10.3390\/molecules26113315","type":"journal-article","created":{"date-parts":[[2021,5,31]],"date-time":"2021-05-31T21:42:06Z","timestamp":1622497326000},"page":"3315","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Tetracyclic Thioxanthene Derivatives: Studies on Fluorescence and Antitumor Activity"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4201-2774","authenticated-orcid":false,"given":"Fernando","family":"Dur\u00e3es","sequence":"first","affiliation":[{"name":"Laboratory of Organic and Pharmaceutical Chemistry, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal"},{"name":"CIIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Novo Edif\u00edcio do Terminal de Cruzeiros do Porto de Leix\u00f5es, Avenida General Norton de Matos s\/n, 4450-208 Matosinhos, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0694-7321","authenticated-orcid":false,"given":"Patr\u00edcia M. A.","family":"Silva","sequence":"additional","affiliation":[{"name":"CESPU, Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS), Rua Central de Gandra, 1317, 4585-116 Gandra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6483-9807","authenticated-orcid":false,"given":"Pedro","family":"Novais","sequence":"additional","affiliation":[{"name":"CESPU, Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS), Rua Central de Gandra, 1317, 4585-116 Gandra, Portugal"},{"name":"Department of Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"given":"Isabel","family":"Amorim","sequence":"additional","affiliation":[{"name":"GreenUPorto (Sustainable Agrifood Production) Research Center, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8352-6539","authenticated-orcid":false,"given":"Lu\u00eds","family":"Gales","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, ICBAS-Instituto de Ci\u00eancias Biom\u00e9dicas Abel Salazar, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal"},{"name":"Bioengineering & Synthetic Microbiology, I3S\u2013Instituto de Investiga\u00e7\u00e3o e Inova\u00e7\u00e3o em Sa\u00fade, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal"}]},{"given":"C\u00e1tia I. C.","family":"Esteves","sequence":"additional","affiliation":[{"name":"LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7439-209X","authenticated-orcid":false,"given":"Samuel","family":"Guieu","sequence":"additional","affiliation":[{"name":"LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4006-5779","authenticated-orcid":false,"given":"Hassan","family":"Bousbaa","sequence":"additional","affiliation":[{"name":"CESPU, Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS), Rua Central de Gandra, 1317, 4585-116 Gandra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4676-1409","authenticated-orcid":false,"given":"Madalena","family":"Pinto","sequence":"additional","affiliation":[{"name":"Laboratory of Organic and Pharmaceutical Chemistry, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal"},{"name":"CIIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Novo Edif\u00edcio do Terminal de Cruzeiros do Porto de Leix\u00f5es, Avenida General Norton de Matos s\/n, 4450-208 Matosinhos, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5397-4672","authenticated-orcid":false,"given":"Em\u00edlia","family":"Sousa","sequence":"additional","affiliation":[{"name":"Laboratory of Organic and Pharmaceutical Chemistry, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal"},{"name":"CIIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Novo Edif\u00edcio do Terminal de Cruzeiros do Porto de Leix\u00f5es, Avenida General Norton de Matos s\/n, 4450-208 Matosinhos, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2438","DOI":"10.2174\/0929867311320190004","article-title":"A century of thioxanthones: Through synthesis and biological applications","volume":"20","author":"Paiva","year":"2013","journal-title":"Curr. 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