Chicory Extracts and Sesquiterpene Lactones Show Potent Activity against Bacterial and Fungal Pathogens

Abstract

Chicory (Cichorium intybus L.) is an important industrial crop cultivated mainly to extract the dietary fiber inulin. However, chicory also contains bioactive compounds such as sesquiterpene lactones and certain polyphenols, which are currently discarded as waste. Plants are an important source of active pharmaceutical ingredients, including novel antimicrobials that are urgently needed due to the global spread of drug-resistant bacteria and fungi. Here, we tested different extracts of chicory for a range of bioactivities, including antimicrobial, antifungal and cytotoxicity assays. Antibacterial and antifungal activities were generally more potent in ethyl acetate extracts compared to water extracts, whereas supercritical fluid extracts showed the broadest range of bioactivities in our assays. Remarkably, the chicory supercritical fluid extract and a purified fraction thereof inhibited both methicillin-resistant Staphylococcus aureus (MRSA) and ampicillin-resistant Pseudomonas aeruginosa IBRS P001. Chicory extracts also showed higher antibiofilm activity against the yeast Candida albicans than standard sesquiterpene lactone compounds. The cytotoxicity of the extracts was generally low. Our results may thus lead to the development of novel antibacterial and antifungal preparations that are both effective and safe for human use.

Keywords: antifungal; antimicrobial; bioactivity; biofilm; chicory; cytotoxicity.

Figure 1

Growth inhibition by Ci_SFE_opt and Ci_SFE_pur at a concentration of 5 mg/mL against (A) S. aureus, and (B) S. aureus MRSA. Green, Ci_SFE_pur; orange, Ci_SFE_opt, black, microbial control.

Figure 2

Bioautographic assay of Ci_SFE_opt and Ci_SFE_pur developed in 85:15 (v/v) dichloromethane:methanol as the solvent. (A) Antibacterial activity against Staphylococcus aureus (oral isolate), S. aureus ATCC (left); and Pseudomonas aeruginosa (right). (B) Antifungal activity against Candida albicans (left) and C. krusei (right). Spots on different Rf values: 1. Rf = 0.18 (activity only against S. aureus ATCC); 2. Rf = 0.20 (activity only against P. aeruginosa); 3. Rf = 0.65 (activity against S. aureus ATCC and C. albicans); 4. Rf = 0.71 (activity against all tested bacteria and fungi); 5. Rf = 0.76 (activity against all tested bacteria and fungi, except C. krusei); 6. Rf = 0.82 (activity against all tested microorganisms, except P. aeruginosa and C. krusei); 7. Rf = 0.88 (activity against all tested bacteria and fungi, except C. krusei).

Figure 3

Percentage inhibition of biofilm formation in (A) C. albicans 475/15 and (B) P. aeruginosa IBRS P001 after treatment with chicory extracts and pure compounds. Results are presented as a mean (± stdev) of triplicates.

Figure 4

Modes of antibiofilm activity against P. aeruginosa IBRS P001 expressed as percentage inhibition compared to the untreated control. (A) Inhibition of biofilm cell viability determined by MTT assay. (B) Inhibition of biofilm exopolysaccharide content. (C) Inhibition of biofilm eDNA. (D) Inhibition of biofilm CFU formed on urinary catheters. Results are expressed as mean (±stdev) of triplicates.

Figure 5

Cytotoxic profile of chicory extracts in Caco-2 cells after incubation for 4 h. (A) Wit_EtOAc. (B) Wit_H₂O. (C) Ci_EtOAc. (D) Ci_SFE_opt. (E) Ci_SFE_pur. Results are presented as mean (±stdev) of three independent experiments.