Research background. Breast cancer is one of the most common cancers and remains a major cause of morbidity and mortality among women worldwide. In developed countries, breast cancer as a multifactorial disease is a major health concern, and its incidence is constantly rising in low and middle-income countries. Numerous studies have demonstrated that phytochemicals such as carotenoids inhibit breast cancer growth and induce apoptosis. We recently enhanced the solubility of capsanthin in water by encapsulating it in diosgenin polyethylene glycol succinate, a novel non-ionic surfactant. Thus, this study aims to evaluate the cytotoxicity of water-soluble capsanthin-loaded micelles in MDA-MB-231 cells in vitro through tetrazolium dye MTT assay. Experimental approach. In the current study, capsanthin, a hydrophobic carotenoid, is extracted from sweet red pepper (Capsicum annuum). Capsanthin-loaded diosgenin polyethylene glycol succinate 1000 (cap-DPGS-1000) micelles were prepared from capsanthin extract (cap) and diosgenin polyethylene glycol succinate 1000 (DPGS-1000) using the solid dispersion method. The capsanthin extract and cap-DPGS-1000 micelles were characterized by UV-visible spectroscopy, high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size distribution, polydispersity, and scanning electron microscopy (SEM). The effects of capsanthin extract and cap-DPGS-1000 micelles on a human triple-negative breast cancer cell line (MDA-MB-231) were tested to check the cell viability, proliferation and cytotoxicity of the micelles. Results and conclusions. The solubility of encapsulated cap-DPGS-1000 micelles in water is greatly enhanced and leads to an increased scope for localized drug delivery, a better delivery option for treating residual cancerous tumours. The encapsulated capsanthin showed a sustained release in simulated intestinal fluid (pH=6.8). Our research proposes a sustained drug delivery system that ensures effective and controlled release to the affected site. The characterization data revealed no change in the structure and functional groups in the encapsulated capsanthin. The IC50 value of the cap-DPGS-1000 micelles against MDA-MB-231 breast cancer cells was (3.10±1.09) μg/mL, which is much lower than of capsanthin extract ((81.1±1.5) μg/mL). Capsanthin extract and capsanthin-loaded micelles are promising drug candidates to induce apoptosis and increase reactive oxygen species (ROS) in cancer cells. Novelty and scientific contribution. The result shows the cytotoxic effect of capsanthin and capsanthin-loaded micelles on MDA-MB-231 cell line for the first time. Capsanthin from sweet red pepper (Capsicum annuum) showed remarkable cytotoxic effect on the triple-negative MDA-MB-231 cell line., Pozadina istraživanja. Karcinom dojke jedan je od najčešćih tipova tumora te je još uvijek glavni uzročnik morbiditeta i mortaliteta među ženama diljem svijeta. U razvijenim zemljama ova multifaktorska bolest predstavlja primarni zdravstveni problem, a u stalnom je porastu u srednje i nisko razvijenim zemljama. Mnoga istraživanja pokazuju da fitokemikalije poput karotenoida suzbijaju rast i potiču apoptozu stanica karcinoma dojke. Nedavno smo poboljšali topljivost kapsantina u vodi postupkom inkapsulacije u novom neionskom surfaktantu, diosgenin polietilenglikol sukcinatu. Stoga je svrha ovoga rada bila pomoću MTT testa ispitati in vitro citotoksičnost micela punjenih kapsantinom, topljivih u vodi, na stanice raka MDA-MB-231. Eksperimentalni pristup. U radu je iz ekstrakta slatke crvene paprike (Capsicum annuum) izoliran hidrofobni karotenoid kapsantin. Iz čvrste disperzije ekstrakta i diosgenin polietilenglikol sukcinata 1000 pripremljene su micele. Ekstrakt kapsantina i micele su okarakterizirani pomoću UV-Vis spektroskopije, visokodjelotvorne tekućinske kromatografije, infracrvene spektroskopije s Fourierovom transformacijom, difrakcije X-zraka, raspodjele veličine čestica, polidisperzije i pretražne elektronske mikroskopije. Ispitali smo učinak ekstrakta kapsantina i micela na preživljavanje i rast trostruko negativnih stanica raka dojke (MDA-MB-231) te citotoksičnost micela. Rezultati i zaključci. Bitno se povećala topljivost kapsantina u inkapsuliranim micelama i time proširila mogućnost njegove primjene za ciljanu isporuku, čime se postižu bolji rezultati u liječenju rezidualnih tumora. Inkapsulirani se kapsantin kontrolirano otpuštao pri simulaciji probave u crijevima (pH=6,8). Predloženi sustav za ciljanu isporuku lijeka s produljenim djelovanjem omogućuje učinkovito i kontrolirano otpuštanje aktivne tvari na mjestu djelovanja. Rezultati pokazuju da se pri inkapsulaciji kapsantina nije promijenila njegova struktura, a niti sastav funkcionalnih skupina. Citotoksičnost micela na stanice MDA-MB-231 (IC50=(3,10±1,09) μg/mL) bila je bitno veća od one ekstrakta kapsantina (IC50=(81,1±1,5) μg/mL). Ekstrakt kapsantina i micele s kapsantinom mogu se upotrijebiti za poticanje apoptoze i povećanje količine reaktivnih kisikovih spojeva u stanicama raka. Novina i znanstveni doprinos. Rezultati prvi put prikazuju citotoksični učinak kapsantina i micela s kapsantinom na stanice raka MDA-MB-231. Kapsantin izoliran iz slatke crvene paprike (Capsicum annuum) imao je izniman citotoksični učinak na trostruko negativne stanice raka MDA-MB-231.