Black turmeric <i>(Curcuma caesia)</i> derived biogenic carbon nanodots: green synthesis, characterization, <i>in vitro</i> antioxidant potential, bio-evaluation studies, and photocatalytic degradation of Rhodamine-B

Black turmeric (kali-haldi), known for its potent bioactive phytoconstituents, possesses significant therapeutic potential with antioxidant and anti-inflammatory properties. A green synthesis approach was employed to develop carbon nanodots (CNDs) from it, aiming to enhance their bioactivity and to explore their applications as sustainable bioactive agents and in photocatalytic strategies. Optimized CNDs were synthesized via calcination at 180 °C and further analyzed using a field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), UV–visible spectroscopy, and surface zeta potential. Comparative evaluations demonstrated that the extract exhibited notable antioxidant (IC50 = 30.02 ± 0.71 µg/mL) and anti-inflammatory (IC50 = 58.61 ± 0.35 µg/mL) activities. In comparison, CNDs showed enhanced performance with lower IC50 values for antioxidant (21.98 ± 0.78 µg/mL) and anti-inflammatory (52.16 ± 0.59 µg/mL) activities. CNDs displayed a strong anticoagulant effect, prolonging coagulation time to 1247 s at 500 µg/mL. Structural characterization confirmed the nanoscale, crystalline nature of the CNDs and attributed the enhanced bioactivity to increased surface area and nanoconfinement effects. Overall, this work highlights the transformative potential of black turmeric (Curcuma caesia)-derived CNDs for the development of future eco-friendly, sustainable nanotherapeutics and environmental remediation agents, subject to in vivo studies, clinical validation, and commercial scale-up.