Co-solvent assisted supercritical fluid extraction of Curcuma caesia Roxb. (black turmeric) as a green and sustainable technology: Its bioactivity and anti-cancer properties

• C. caesia (black turmeric) was extracted by supercritical fluid extraction (SFE). • SFE at 350 bar/65 °C/150 min/30 % v/v ethanol yielded 10 g oleoresin/100 g. • BTO had high flavonoid content, antioxidant activity and anti-inflammatory properties. • BTO showed antimicrobial activity against Gram-positive and Gram-negative bacteria. • BTO showed cytotoxicity against HPAC (IC 50 5 µL/mL) and HepG2 (IC 50 6 µL/mL). This study investigates a green method to extract black turmeric oleoresin (BTO) using supercritical fluid extraction (SFE) with ethanol as co-solvent. The optimized parameters of SFE were 350 bar/65 °C/150 min, yielding 6.56 g oleoresin/100 g dwb and 134 μg total curcuminoids/ g dwb (dry weight basis). The conventional ethanol extraction gave 13.94 g/100 g oleoresin, and the total curcuminoids in the oleoresin was 128 µg/g dwb. Hence ethanol was used as a co-solvent and this approach increased the yield of the oleoresin to 12.53 g/100 g and curcuminoids (223 µg/g) among all the methods. The SFE+ co-solvent extracted BTO showed significant antioxidant activity. Phytochemicals present in extracted oleoresin were quantified using HPLC, LC HRMS, GCMS, and FTIR. Similarly, a comparatively higher (84 %) anti-inflammatory activity compared to diclofenac and bactericidal effects against Salmonella typhi, Pseudomonas aeruginosa and Listeria monocytogenes have been observed. The remarkable in vitro anticancer activity of the extract in HepG2 (IC 50 : 6 µL/mL) and HPAC (IC 50 : 5 µL/mL) cell lines indicated the potency of the extract.