Optimization of callus cultures at Echinacea purpurea L. for the amount of caffeic acid derivatives

BACKGROUND: In order to produce an effective callus in Echinacea purpurea L.; determination of the explant type and growth regulators that best respond to callus induction and the optimization of the culture conditions to increase the amount of caffeic acid derivatives (CADs) in the obtained callus. CADs contents of callus cultures of E. purpurea were evaluated by establishing an effective callus induction system in vitro. RESULTS: Various medium containing different growth regulators were tested using leaf, petiole, cotyledon and root as the explants. The best callus development was achieved in MS medium with 1.0 mg l 1 2,4- D + 2.0 mg l 1 BAP in leaf, 1.0 mg l 1 NAA + 0.5 mg l 1 TDZ in petiole, 2.0 mg l 1 NAA + 1.0 mg l 1 TDZ in cotyledon and 0.5 mg l 1 NAA + 0.5 mg l 1 BAP in roots. Upon optimisation of callus growth, each type of explant was cultured for 4, 6, 8 and 10 weeks in medium for the analyses of caftaric acid, chlorogenic acid, caffeic acid and chicoric acid contents. The highest amounts of caftaric acid (4.11 mg/g) and chicoric acid (57.89 mg/g) were found from petiole explants and chlorogenic acid (8.83 mg/g) from root explants at the end of the 10-week culture time. CONCLUSIONS: As a result of the present study, the production of caffeic acid derivatives was performed by providing the optimization of E. purpurea L. callus cultures. Effective and repeatable protocols established in this study may offer help for further studies investigating the production of caffeic acid derivatives in vitro.

In vitro evaluation of caffeic acid derivatives as efflux pump inhibitor in Pseudomonas aeruginosa and Burkholderia pseudomallei

Aims: Bacterial pathogens such as Pseudomonas aeruginosa and Burkholderia pseudomallei are intrinsically resistant to many classes of antibiotics. This is not only due to the poor permeability of their outer membrane but also because of expression of multiple efflux pumps. A promising strategy to minimize the efflux of drugs by these pumps is the use of efflux pump inhibitors (EPIs). In this study, the potential of caffeic acid derivatives as EPIs in P. aeruginosa and B. pseudomallei were evaluated. Methodology and results: The potential of caffeic acid and its derivatives, i.e. chlorogenic acid, caffeic acid phenethyl ester (CAPE) and caffeic acid phenethyl amide (CAPA) to act as EPIs in P. aeruginosa and B. pseudomallei were assessed using the ethidium bromide (EtBr) accumulation and minimum inhibitory concentration (MIC) validation assays. Among the four test compounds, CAPE was found to significantly increased intracellular accumulation of EtBr in both P. aeruginosa and B. pseudomallei. An increase of 21.4% and 16.8% in cell fluorescence, over a 5-min time frame was observed in P. aeruginosa and B. pseudomallei respectively. Combination of CAPE with kanamycin significantly reduced MICs of this aminoglycoside by a factor of 8-fold in P. aeruginosa and 2-fold in B. pseudomallei. Combination of CAPE with gentamicin also led to a reduction of 4-fold MIC value of this antibiotic in B. pseudomallei. Conclusion, significance and impact of study: The in-vitro results suggest that CAPE has the potential to act as an EPI in P. aeruginosa and B. pseudomallei, thus improving the efficacy of aminoglycosides as antimicrobial agents.