{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,14]],"date-time":"2026-03-14T05:16:34Z","timestamp":1773465394073,"version":"3.50.1"},"reference-count":28,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,6,5]],"date-time":"2025-06-05T00:00:00Z","timestamp":1749081600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"PRIN_2022PNRR_P2022KCW3L_002","award":["CUP J53D23014810001"],"award-info":[{"award-number":["CUP J53D23014810001"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceuticals"],"abstract":"<jats:p>Background\/Objectives: Rhodesain is a cysteine protease crucial for the life cycle of Trypanosoma brucei rhodesiense, a parasite that causes the lethal form of human African trypanosomiasis. For these reasons, rhodesain is considered an important target for the drug discovery process of novel antitrypanosomal agents. Methods: In the present work, we carried out a combination study of two novel synthetic nitriles, Nitrile 1 and Nitrile 2, with curcumin, the golden multitarget nutraceutical obtained from Curcuma longa L., which we demonstrated to inhibit rhodesain in a non-competitive manner. We calculated the combination index (CI) in both the combination studies by using the Chou and Talalay method. Results: Comparing the CI values of the combinations Nitrile 1 + curcumin and Nitrile 2 + curcumin, we assessed that the inhibitory effect of the combination Nitrile 2 + curcumin against rhodesain was much more potent than that of the other combination. At the IC50 value, in the case of the combination Nitrile 1 + curcumin an additive effect occurred, while in the case of Nitrile 2 + curcumin, we observed a moderate synergism: at 99% of the effect, the synergism induced by the combination Nitrile 2 + curcumin was much stronger than the synergism promoted by the combination Nitrile 1 + curcumin (CI = 0.3843 vs 0.6622, respectively). Conclusions: The co-administration of dipeptide nitriles with curcumin enhances rhodesain inhibition through synergistic effects. Notably, Nitrile 2 + curcumin exhibits a stronger synergy at higher inhibition levels, indicating a greater therapeutic potential.<\/jats:p>","DOI":"10.3390\/ph18060847","type":"journal-article","created":{"date-parts":[[2025,6,6]],"date-time":"2025-06-06T03:52:28Z","timestamp":1749181948000},"page":"847","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Synthesis and Combination Studies of Novel Dipeptide Nitriles with Curcumin for a Potent Synergistic Action Against Rhodesain, Cysteine Protease of Trypanosoma brucei rhodesiense"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3191-3932","authenticated-orcid":false,"given":"Carla","family":"Di Chio","sequence":"first","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-9875-7383","authenticated-orcid":false,"given":"Jos\u00e8","family":"Starvaggi","sequence":"additional","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8473-3321","authenticated-orcid":false,"given":"Santo","family":"Previti","sequence":"additional","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-3431-9421","authenticated-orcid":false,"given":"Fabiola","family":"De Luca","sequence":"additional","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-2065-2535","authenticated-orcid":false,"given":"Benito","family":"Natale","sequence":"additional","affiliation":[{"name":"Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania Luigi Vanvitelli, Via A. Vivaldi 43, 81100 Caserta, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8900-0968","authenticated-orcid":false,"given":"Sandro","family":"Cosconati","sequence":"additional","affiliation":[{"name":"Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania Luigi Vanvitelli, Via A. Vivaldi 43, 81100 Caserta, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tanja","family":"Schirmeister","sequence":"additional","affiliation":[{"name":"Institute of Pharmacy and Biochemistry, University of Mainz, Staudingerweg 5, DE 55128 Mainz, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8942-797X","authenticated-orcid":false,"given":"Maria","family":"Zappal\u00e0","sequence":"additional","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9020-2068","authenticated-orcid":false,"given":"Roberta","family":"Ettari","sequence":"additional","affiliation":[{"name":"Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d\u2019Alcontres 31, 98166 Messina, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,5]]},"reference":[{"key":"ref_1","unstructured":"(2025, April 04). Neglected Tropical Diseases. Available online: https:\/\/www.who.int\/health-topics\/neglected-tropical-diseases#tab=tab_1."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2397","DOI":"10.1016\/S0140-6736(17)31510-6","article-title":"Human African Trypanosomiasis","volume":"390","author":"Cecchi","year":"2017","journal-title":"Lancet"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"MacLean, L., Reiber, H., Kennedy, P.G., and Sternberg, J.M. (2012). Stage Progression and Neurological Symptoms in Trypanosoma Brucei Rhodesiense Sleeping Sickness: Role of the CNS Inflammatory Response. PLoS Neglect. Trop. Dis., 6.","DOI":"10.1371\/journal.pntd.0001857"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Kennedy, P.G.E., and Rodgers, J. (2019). Clinical and neuropathogenetic aspects of human african trypanosomiasis. Front. Immunol., 10.","DOI":"10.3389\/fimmu.2019.00039"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Papagni, R., Novara, R., Minardi, M.L., Frallonardo, L., Panico, G.G., Pallara, E., Cotugno, S., Ascoli Bartoli, T., Guido, G., and De Vita, E. (2023). Human african trypanosomiasis (sleeping sickness): Current knowledge and future challenges. Front. Trop. Dis., 4.","DOI":"10.3389\/fitd.2023.1087003"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Barrett, M.P. (2025). Transforming the chemotherapy of human African trypanosomiasis. Clin. Microbiol. Rev., 38.","DOI":"10.1128\/cmr.00153-23"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"e77","DOI":"10.1016\/S1473-3099(24)00581-4","article-title":"New WHO guidelines for treating rhodesiense human African trypanosomiasis: Expanded indications for fexinidazole and pentamidine","volume":"25","author":"Lindner","year":"2025","journal-title":"Lancet Infect. Dis."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e900","DOI":"10.1016\/S2214-109X(24)00526-6","article-title":"Effectiveness and safety of fexinidazole for gambiense human African trypanosomiasis and exploration of adherence in outpatients: A phase 3b, prospective, open-label, non-randomised, cohort study","volume":"13","author":"Kumeso","year":"2025","journal-title":"Lancet Glob. Health"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2952","DOI":"10.2174\/0929867328666210810125309","article-title":"Dual Inhibition of Parasitic Targets: A Valuable Strategy to Treat Malaria and Neglected Tropical Diseases","volume":"29","author":"Previti","year":"2022","journal-title":"Curr. Med. Chem."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"de Jesus Marinho, W.P., de Oliveira Rios, \u00c9., de Moura, R.O., and Nascimento, I.J.D.S. Target Selectivity of Cysteine Protease Inhibitors: A Strategy to Address Neglected Tropical Diseases. Curr. Med. Chem., 2025.","DOI":"10.2174\/0109298673359768250317055418"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0166-6851(01)00438-8","article-title":"Cysteine proteases of parasitic organisms","volume":"120","author":"Sajid","year":"2002","journal-title":"Mol. Biochem. Parasitol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2739","DOI":"10.1172\/JCI27798.","article-title":"Blood-brain barrier traversal by African trypanosomes requires calcium signaling induced by parasite cysteine protease","volume":"116","author":"Nikolskaia","year":"2006","journal-title":"J. Clin. Investig."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0065-308X(01)49037-3","article-title":"Antigenic variation in trypanosomes: Enhanced phenotypic variation in a eukaryotic parasite","volume":"49","author":"Barry","year":"2001","journal-title":"Adv. Parasitol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"739","DOI":"10.1515\/BC.2002.077","article-title":"Congopain from Trypanosoma congolense: Drug target and vaccine candidate","volume":"383","author":"Lalmanach","year":"2002","journal-title":"Biol. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1016\/S0166-6851(01)00368-1","article-title":"Active site mapping, biochemical properties and subcellular localization of rhodesain, the major cysteine protease of Trypanosoma brucei rhodesiense","volume":"118","author":"Caffrey","year":"2001","journal-title":"Mol. Biochem. Parasitol."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Previti, S., Ettari, R., Di Chio, C., Ravichandran, R., Bogacz, M., Hellmich, U.A., Schirmeister, T., Cosconati, S., and Zappal\u00e0, M. (2022). Development of Reduced Peptide Bond Pseudopeptide Michael Acceptors for the Treatment of Human African Trypanosomiasis. Molecules, 27.","DOI":"10.3390\/molecules27123765"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"114328","DOI":"10.1016\/j.ejmech.2022.114328","article-title":"Development of novel dipeptide nitriles as inhibitors of rhodesain of Trypanosoma brucei rhodesiense","volume":"236","author":"Previti","year":"2022","journal-title":"Eur. J. Med. Chem."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Swenson, C.E., Hunt, W.R., Manfredi, C., Beltran, D.J., Hong, J.S., Davis, B.R., Suzuki, S., Barill\u00e1, C., Rab, A., and Chico, C. (2025). Evaluating elexacaftor\/tezacaftor\/ivacaftor (ETI Trikafta\u2122) for treatment of patients with non-cystic fibrosis bronchiectasis (NCFBE): A clinical study protocol. PLoS ONE, 20.","DOI":"10.1371\/journal.pone.0316721"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Porcel-Pastrana, F., Montero-Hidalgo, A.J., G-Garc\u00eda, M.E., Gil-Duque, I., Prats-Escribano, A., Gahete, M.D., Sarmento-Cabral, A., Luque, R.M., and Le\u00f3n-Gonz\u00e1lez, A.J. (2025). Cellular and Molecular Evidence of the Synergistic Antitumour Effects of Hydroxytyrosol and Metformin in Prostate Cancer. Int. J. Mol. Sci., 26.","DOI":"10.3390\/ijms26031341"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"101947","DOI":"10.1016\/j.xcrm.2025.101947","article-title":"Estimating the treatment effects of multiple drug combinations on multiple outcomes in hypertension","volume":"6","author":"Liu","year":"2025","journal-title":"Cell Rep. Med."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"e240183","DOI":"10.1590\/0074-02760240183","article-title":"Looking for ap-proved-medicines to be repositioned as anti-Trypanosoma cruzi agents. Identification of new chemo-types with good individual- or in combination-biological behaviours","volume":"120","author":"Veira","year":"2025","journal-title":"Mem. Inst. Oswaldo Cruz."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2456890","DOI":"10.1080\/25787489.2025.2456890","article-title":"Bictegravir\/emtricitabine\/tenofovir alafenamide in clinical practice for people with HIV: Final 24-month effectiveness and safety outcomes in key populations in the observational BICSTaR cohort","volume":"26","author":"Trottier","year":"2025","journal-title":"HIV Res. Clin. Pract."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"806","DOI":"10.1021\/acsmedchemlett.9b00635","article-title":"Drug synergism: Studies of combination of RK-52 and curcumin against rhodesain of Trypanosoma brucei rhodesiense","volume":"11","author":"Ettari","year":"2020","journal-title":"ACS Med. Chem. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Jacob, S., Kather, F.S., Morsy, M.A., Boddu, S.H.S., Attimarad, M., Shah, J., Shinu, P., and Nair, A.B. (2024). Advances in Nanocarrier Systems for Overcoming Formulation Challenges of Curcumin: Current Insights. Nanomaterials, 14.","DOI":"10.3390\/nano14080672"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Yakubu, J., and Pandey, A.V. (2024). Innovative Delivery Systems for Curcumin: Exploring Nanosized and Conventional Formulations. Pharmaceutics, 16.","DOI":"10.3390\/pharmaceutics16050637"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"440","DOI":"10.1158\/0008-5472.CAN-09-1947","article-title":"Drug Combination Studies and Their Synergy Quantification Using the Chou-Talalay Method","volume":"70","author":"Chou","year":"2010","journal-title":"Cancer Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/0065-2571(84)90007-4","article-title":"Quantitative Analysis of Dose-Effect Relationships: The Combined Effects of Multiple Drugs or Enzyme Inhibitors","volume":"22","author":"Chou","year":"1984","journal-title":"Adv. Enzyme Regul."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"8332","DOI":"10.1021\/jacs.6b03052","article-title":"Quantum chemical-based protocol for the rational design of covalent inhibitors","volume":"138","author":"Schirmeister","year":"2016","journal-title":"J. Am. Chem. Soc."}],"container-title":["Pharmaceuticals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8247\/18\/6\/847\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:47:22Z","timestamp":1760032042000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8247\/18\/6\/847"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,6,5]]},"references-count":28,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2025,6]]}},"alternative-id":["ph18060847"],"URL":"https:\/\/doi.org\/10.3390\/ph18060847","relation":{},"ISSN":["1424-8247"],"issn-type":[{"value":"1424-8247","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,5]]}}}