Phytochemical investigation and antibacterial activity of Curcuma longa against multi-drug resistant bacteria

Abstract

Emergence of antibiotic resistance in bacterial species is increasing at an alarming rate. This calls for an urge to search for new antimicrobial agents from natural sources. Curcuma longa rhizome is used in traditional medicine as a remedy for many infectious diseases. The rhizome extracted in different solvents is tested against hospital isolates of multidrug-resistant bacteria (Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa) using agar well diffusion and broth microdilution assays. Antioxidant activity was determined using DPPH radical scavenging and superoxide anion scavenging methods. GC–MS analysis was performed to identify biologically active compounds present in the plant. All the plant samples inhibited bacterial growth with varying degree of inhibition observed for different bacterial strains. In general MRSA was more sensitive to most of the extracts with larger zones of inhibition and high percentage inhibition while A. baumannii was the most resistant with smaller zones of inhibition and low percentage inhibition observed for different plant samples. n-Hexane fraction of C. longa was the most effective in inhibiting bacterial growth with lowest MIC values (2.5 mg/mL). Antioxidant activity assays indicated strong antioxidant potential of n-hexane fraction in DPPH assay and of methanol fraction in superoxide scavenging assay. GC–MS analysis indicated ar-turmerone as the most abundant component of the plant (34.63 %). The non-polar fractions of the plant were particularly more effective against multidrug-resistant bacteria. Further purification and characterization of bioactive compounds, from active fractions of this plant, for their applications as antibacterial leads in pharmaceutical industries is recommended.