Polarity-driven extraction revealed potent bioactivities in rhizomes and leaves of Curcuma caesia Roxb.

The increasing demand for plant-based bioactive compounds has fueled interest in exploring natural antioxidants and antimicrobial agents. Curcuma caesia Roxb., commonly known as black turmeric, holds significant potential as a source of natural antioxidants and antimicrobial agents. This study investigated the antioxidant and antimicrobial potential of sequential extracts from C. caesia rhizomes and leaves, utilizing solvents of varying polarity (n-hexane, chloroform, ethyl acetate, methanol and water). The extraction yields varied between 1.69% and 6.34%, with n-hexane providing the highest yield of 6.34% for leaf extracts and 5.9% for rhizome extracts. Chloroform extracts were particularly rich in phenolics (total phenolic content: 95.17 ± 0.15 mg GAE/g for leaves and 84.16 ± 0.20 mg GAE/g for rhizome) and flavonoids (total flavonoids content: up to 75.98 ± 2.00 mg quercetin/g for leaves and 56.89 ± 0.15 mg quercetin/g for rhizomes). Antioxidant activity, determined through 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, showed the strongest results in chloroform extracts, with IC50 values as low as 0.75 ± 0.02 microgram/mL for leaves. Additionally, nonpolar solvent extracts (n-hexane and chloroform) demonstrated significant antimicrobial activity against multidrug-resistant strains like Klebsiella pneumoniae and Staphylococcus aureus, with minimum inhibitory concentration (MIC) values as low as 3.12 microgram/mL, comparable to standard antibiotics. These findings highlight C. caesia as a promising source of bioactive compounds for future phytopharmaceutical applications.