Evaluation of antimicrobial activity of Curcuma longa L. against beneficial and pathogenic human gastrointestinal microorganisms

Tran, Hoang; Adukwu, Emmanuel; Mackonochie, Marion; Rolfe, Vivien

Abstract

Introduction: Curcuma longa L. (turmeric) is very popular worldwide as a spice, food preservative, and colouring material. Curcuminoids and turmerones are two major chemical components of turmeric. Many studies have been conducted to test the antimicrobial activity of turmeric powder and extracts. Their antimicrobial activities, however, vary widely, depending on the microorganism (Lawhavinit, 2010).

Aims: The aim of this study was to investigate the in vitro antimicrobial activity of turmeric whole powder, curcumin extracts, turmerone extracts and turmeric essential oil against both beneficial and pathogenic gastrointestinal microorganisms.

Methods: Eight microorganisms were used in this study which included seven strains of common gut bacteria; Escherichia coli B, E. coli O157 pLITE, Bacillus subtilis SASP, B. subtilis NPCT 10400, Lactobacillus rhamnosus GG, L. casei Shirota and Staphylococcus aureus and one strain of fungi; Candida albicans ATCC 10231. The disc diffusion and broth microdilution method was used to determine antimicrobial activity of turmeric compounds against the test microorganisms. The viability of bacterial and fungal cells in human gastrointestinal tract after exposure to turmeric was determined using the simulated gastric fluid assay.

Results: All tested strains resisted to turmeric whole powder. All inhibitory zones observed after exposure to a 6-mm paper disc impregnated with 10 μL of dissolved turmeric whole powder were approximately 6.5 mm in diameter. Amongst all tested organisms, C. albicans and S. aureus showed the greatest susceptibility to curcumin with inhibitory zones approximate 8.2 mm and 7.6 mm, respectively. In the broth micro dilution test, the minimum inhibitory concentration (MIC) and minimum fungicidal concentrations (MFC) of curcumin for C. albicans was 10-20 mg/ml and 20 mg/ml, respectively. For all other bacterial strains, the MICs of curcumin was over 20 mg/ml but not excess 80 mg/ml. In the simulation gastric fluid assay, turmeric whole powder and curcumin decreased the viability of C. albicans, B. subtilis SASP and E. coli pLITE by 0.87 to 3.38 log, after 90 mins exposure to acidic gastric fluid (pH=2). Under the neutral pH condition (pH = 7), the viable count of E. coli pLITE after turmeric whole powder and curcumin treatment was 1.74 log and 0.2 log higher than that at acidic pH.

Conclusion: Turmeric whole powder, turmeric essential oil and turmerones have no antimicrobial effect against 8 selected gut microorganisms. Curcumin showed very weak antifungal activity against C. albicans. However, turmeric whole powder might reduce the viable count of some pathogenic organisms, especially C. albicans in human gastrointestinal tract.

• Presentation Conference Type: Poster
• Conference Name: American Biomedical Research Conference for Minority Students
• Start Date: Nov 9, 2020
• End Date: Nov 13, 2020
• Deposit Date: May 18, 2021
• Public URL: https://uwe-repository.worktribe.com/output/7406317