<p>Hepatocellular carcinoma (HCC) continues to be a significant cancer in India, exhibiting a yearly incidence of about 1.6%. The limitations of conventional chemotherapy, such as systemic toxicity and drug resistance, highlight the need of natural chemosensitizers in improving therapeutic outcomes. This study assesses the chemosensitizing ability of Black Grape Anthocyanins (BGA) derived from the Manjari Medika (MM) grape variety to improve the efficacy of low-dose 5-Fluorouracil (5-FU) in HepG2 cells. MM grapes are high in polyphenols and contains 12 different anthocyanin derivatives, as determined by Liquid Chromatography-Mass spectrometry (LC-MS) analysis. HepG2 cells were treated with varying concentrations of 5-FU and BGA, both alone and in combination, and their viability, ROS generation, mitochondrial integrity, calcium influx, apoptosis, and autophagy indicators were measured using biochemical and imaging methods. Co-treatment with 5-FU (50 µM) and BGA (80&#xa0;µg/ml) significantly increased cytotoxicity compared to individual therapies. The combination caused significant cytosolic calcium influx as well as enhanced intracellular and mitochondrial reactive oxygen species (ROS), resulting in mitochondrial depolarisation and structural disintegration. These changes stimulated intrinsic apoptotic signalling, as evidenced by higher Bax and cleaved Caspase-3 expression and lower Bcl-2 levels. Autophagic flux increased concurrently, as demonstrated by overexpression of LC3A/B and Beclin 1 (2.36 and 1.27-fold, respectively). ROS scavenging with NAC reduced these effects, establishing ROS as an important upstream mediator. Importantly, BGA showed little cytotoxicity in primary hepatocytes. Overall, BGA works as a strong, selective chemosensitiser that improves 5-FU efficacy via ROS-mediated regulation of calcium signalling, apoptosis, and autophagy in HCC cells.</p>