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Background and Aim: Bacillus cereus and Staphylococcus aureus cause foodborne intoxication in humans and animals. Pathogens can produce biofilms controlled by the quorum sensing system. The study aimed to investigate the antibacterial, antibiofilm, and anti-quorum sensing activities of Coffea canephora P. ex Fr. (Robusta coffee) extracts against B. cereus and S. aureus. Materials and Methods: Ethanol extracts of fruit peels and seeds of Robusta coffee were tested for antibacterial activity against B. cereus and S. aureus using a broth microdilution assay. Reduction of the biofilm formation and elimination of the viability of mature biofilm-grown cells of B. cereus and S. aureus were determined. Inhibition of quorum sensing activity in Chromobacterium violaceum by the extracts was investigated using the disk diffusion method and flask incubation assay. Results: Fresh fruit peel extract showed the strongest antibacterial activity against B. cereus and S. aureus with minimum inhibitory concentration (MIC) values of 2 and 4 mg/mL, respectively. However, the extracts did not inhibit Escherichia coli, avian pathogenic E. coli, and Pseudomonas aeruginosa at 8 mg/mL. Significant inhibition of biofilm formation at 1/2 × MIC of the fresh peel extract was detected in B. cereus (56.37%) and S. aureus (39.69 %), respectively. At 8 × MIC of the fresh peel extract, a significant elimination of the mature biofilm viability was detected in B. cereus (92.48%) and S. aureus (74.49%), respectively. The results showed that fresh and dried peel fruit extracts at 1/2 × MIC significantly reduced violacein production with the highest percentage inhibition ranging from 44.53 to 47.48% at 24 h (p ≤ 0.05). Conclusion: The results of the present study suggest the potential therapeutic benefits of Robusta coffee extracts in inhibiting the growth, biofilm, and quorum sensing of both B. cereus and S. aureus. The results put forward an alternative strategy to control the foodborne intoxications caused by both pathogens.
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OBJECTIVE: To evaluate the cytotoxic, apoptotic, mutagenic and immunomodulatory activities of Kaempferia galanga Linn. (KG) extract and ethyl-p-methoxycinnamate (EPMC) in vitro. METHODS: The present study investigated the cytotoxic [using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide test], apoptotic (using a mitochondrial membrane potential assay), mutagenic (using a micronucleus test) and immunomodulatory (using flow cytometry) activities of the ethanolic extract of KG and its bioactive component, EPMC, against two cholangiocarcinoma (CCA) cell lines, CL-6 and HuCCT1, and one normal human cell line, OUMS-36T-1F. RESULTS: Both KG extract and EPMC exhibited moderate cytotoxic activity against both CCA cells. The cytotoxic activity was supported by their concentration-dependent induction of apoptosis. CL-6 was most sensitive (3-4 fold) and selective to 5-fluorouracil (5-FU), compared with KG extract and EPMC [median half inhibiting concentration (IC50) and selectivity index (SI) were 23.01 µg/mL and 17.32; 78.41 µg/mL and 4.44; 100.76 µg/mL and 2.20, respectively for 5-FU vs. KG extract vs. EPMC]. HuCCT1 was relatively more sensitive and selective to 5-FU and EPMC than KG extract [median IC50 and SI were 66.03 µg/mL and 6.04; 60.90 µg/mL and 3.65; 156.60 µg/mL and 2.23, respectively for 5-FU vs. EPMC vs. KG extract]. EPMC produced relatively potent cytotoxic activity against polymorphonuclear cells (IC50 = 92.20 µg/mL). KG extract and EPMC exhibited concentration-dependent mutagenic activity, as well as inhibition of tumor necrosis factor-α and interleukin-6. CONCLUSION: Considering cytotoxic, apoptotic, immunomodulatory and mutagenic activities, further development of KG as a drug candidate is likely to focus on the oral pharmaceutical formulation of a standardized KG extract rather than isolated compounds.
