{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,9]],"date-time":"2025-11-09T17:56:15Z","timestamp":1762710975247,"version":"build-2065373602"},"reference-count":33,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2020,4,7]],"date-time":"2020-04-07T00:00:00Z","timestamp":1586217600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004329","name":"Javna Agencija za Raziskovalno Dejavnost RS","doi-asserted-by":"publisher","award":["No. P1-0005","No. P1-0242"],"award-info":[{"award-number":["No. P1-0005","No. P1-0242"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Slovenian Ministry of Education Science and Sport &amp; EU \u2013 European Regional Development Fund","award":["C3330-17-529013"],"award-info":[{"award-number":["C3330-17-529013"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>d-cycloserine is a broad-spectrum antibiotic that is currently being used as a secondary choice in the treatment of tuberculosis. In recent years, it has become more popular, due to its effect on the nervous system. In this current study, we provide evidence that The International Pharmacopoeia HPLC\u2013UV method for d-cycloserine impurity profiling is not repeatable due to the variable response of cycloserine dimer, one of d-cycloserine impurities. Therefore, we introduced the DOSY (diffusion ordered spectroscopy) NMR (nuclear magnetic resonance) technique to determine the levels of d-cycloserine impurities in pharmaceutical dosage forms. The DOSY NMR technique allowed separation of d-cycloserine, its degradation products, and key process impurities in concentrations below pharmacopoeial specification limits. The proposed DOSY NMR method allowed accurate identification and quantification of the cycloserine dimer, which was not possible through the use of the pharmacopoeial HPLC method. The current method has the potential for practical use in analytical laboratories of the pharmaceutical industry.<\/jats:p>","DOI":"10.3390\/molecules25071684","type":"journal-article","created":{"date-parts":[[2020,4,10]],"date-time":"2020-04-10T05:31:16Z","timestamp":1586496676000},"page":"1684","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Determination of d-Cycloserine Impurities in Pharmaceutical Dosage Forms: Comparison of the International Pharmacopoeia HPLC\u2013UV Method and the DOSY NMR Method"],"prefix":"10.3390","volume":"25","author":[{"given":"Damjan","family":"Makuc","sequence":"first","affiliation":[{"name":"Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1616-5101","authenticated-orcid":false,"given":"\u017diva","family":"\u0160vab","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ve\u010dna pot 113, SI-1001 Ljubljana, Slovenia"},{"name":"Lek Pharmaceuticals d.d., Sandoz Development Center Slovenia, Verov\u0161kova ulica 57, SI-1526 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1087-0694","authenticated-orcid":false,"given":"Katerina","family":"Naumoska","sequence":"additional","affiliation":[{"name":"Department of Food Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1570-8602","authenticated-orcid":false,"given":"Janez","family":"Plavec","sequence":"additional","affiliation":[{"name":"Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia"},{"name":"Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ve\u010dna pot 113, SI-1001 Ljubljana, Slovenia"},{"name":"EN-FIST Centre of Excellence, Trg Osvobodilne fronte 13, SI-1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6689-3353","authenticated-orcid":false,"given":"Zdenko","family":"\u010casar","sequence":"additional","affiliation":[{"name":"Lek Pharmaceuticals d.d., Sandoz Development Center Slovenia, Verov\u0161kova ulica 57, SI-1526 Ljubljana, Slovenia"},{"name":"University of Ljubljana, Faculty of Pharmacy, A\u0161ker\u010deva cesta 7, SI-1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"691","DOI":"10.1517\/14728222.2014.902937","article-title":"Molecular basis underlying Mycobacterium tuberculosis d-cycloserine resistance. 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