Bioactivity Screening of Thirty Black Turmeric (Curcuma caesia Roxb.) Essential Oils Against Free Radicals and MDR Isolates

Background Curcuma caesia Roxb. (Black turmeric) is a perennial medicinal herb belonging to the Zingiberaceae family that is endangered in Southeast Asia. It is treasured for its high-quality essential oil with tremendous medicinal and aromatic properties. In the present scenario, C. caesia Roxb. is an unexplored plant for drug discovery. Objectives The present study was undertaken to compare the bioactivities of Thirty C. caesia rhizomes and leaf oils collected from various eco-regions of Eastern India. Materials and Methods The comparative antioxidant and antimicrobial activities of leaf and rhizome essential oils from different eco-regions of Eastern India were assessed. The antioxidant activities were evaluated against standards like butylated hydroxytoluene (BHT) and ascorbic acid by the 2,2-diphenyl-1-picrylhydrazyl and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assays. Moreover, the essential oils were also evaluated for their antimicrobial activity using the broth micro-dilution assay for minimum inhibitory concentrations (MIC) against multidrug resistant strains. Results Leaf essential oils exhibited a considerable level of antioxidant potential as compared to rhizome essential oils and standard BHT. Furthermore, the essential oils also possessed a significant level of inhibitory activity against three multidrug-resistant (MDR) strains, such as Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae. The rhizome essential oils had shown the most effective antimicrobial activity against A. baumannii (MIC: 0.09 to 6.25 µg/mL) when compared with the positive control, ampicillin (MIC: 25 µg/mL). Conclusion The variability in bioactivities was greatly influenced by geographical origin. The identified accessions of C. caesia, that is, Cc 26 with better bioactivity potential, might be useful for formulating drugs in the future.