Synergistic antibacterial activity of Curcuma longa L. and Urtica dioica L. extracts and preservatives

Marina Stanković,Jelena Terzić,Olgica Stefanović

doi:10.5937/kgjsci1941107s

Abstract

Curcuma longa L. (turmeric) and Urtica dioica L. (common nettle) are well-known medicinal plants. In recent decades, due to its excellent biological activity and low toxicity, significant efforts have been made to research the potential application of these plants. Accordingly, the aim of this study was to investigate the combined effects of preservatives (potassium nitrite and sodium nitrite) and ethanol, acetone, and ethyl acetate extracts of C. longa and U. dioica emphasizing their join, synergistic effects. The eight isolates of foodborne pathogenic bacteria and two reference strains were used. The interactions were tested by the checkerboard method and expressed as fractional inhibitory concentration (FIC) index. FIC index was ranged in intervals from 0.25 to 2.0. The extracts of C. longa showed better synergistic effect with preservatives than U. dioica extracts. Synergism was observed in relation to Staphylococcus aureus ATCC 25923, S. aureus, Bacillus subtilis, and Salmonella typhimurium. In the presence of subinhibitory concentrations (1/4 MIC, 1/8 MIC) of the extracts, the MICs of preservatives have decreased up to 8-fold. In addition, the contents of phenolic compounds (total phenols, flavonoids, tannins, and proanthocyanidins) were determined spectrophotometrically. The higher concentration of phenolic compounds was detected in C. longa extracts than in U. dioica extracts.

Highlights

The great need for high-quality and safe food requires new, natural methods of longterm storage of food
It can be seen that the higher concentration of phenolic compounds was detected in C. longa extracts than in U. dioica extracts
C. longa ethyl acetate extract contented the highest quantity of phenolic compounds, ethyl acetate could be a solvent of choice for extraction of bioactive compounds from C. longa plant material

Summary

Introduction

The great need for high-quality and safe food requires new, natural methods of longterm storage of food This presents significant challenges, especially because there is growing disagreement regarding the use of chemical preservatives and artificial antimicrobial agents. In recent years, the natural antimicrobial compounds isolated from plants have been gaining in importance These compounds control the microbial contamination of food inhibiting the growth of microorganisms, increase the duration of canned food, and they are recognized as safe for human health (TAJKARIMI et al, 2010). Plants produce bioactive substances which arise as a secondary metabolism products which exhibit antimicrobial, antioxidant, antiinflammatory, anticancer and other biological properties. Thanks to their bioactive metabolites, some plants have been used for a long time in traditional medicine, the effect of which has been confirmed by scientific researches. The bioactive substances isolated from the plants are classified in the three groups: phenolic compounds (phenols, flavonoids, tannins, coumarins, proanthocyanidins), alkaloids and terpenoids (COWAN et al, 2010)

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