In vitro growth-inhibitory effects of phytochemicals and their synthetic analogs against intestinal bacteria associated with colorectal cancer

Colorectal cancer (CRC), defined as an adenocarcinoma of large intestine, is the second most deadly cancer that caused 0.9 million deaths in 2020 worldwide [1]. China and the United States have the highest estimated number of new cases [2]. Gut dysbiosis is one of the factors associated with an increased risk of developing intestinal cancer. Various phytochemicals and their synthetic analogs (e.g., quinoline derivates) have been found to inhibit gut pathogenic microorganisms [3], however, their effect on CRC associated microorganisms has not been determined yet. Therefore, the aim of this study was to test in vitro growth-inhibitory effects of ten substances (berberine, bismuth subsalicylate, ferron, 8-hydroxyquinoline, chloroxine, nitroxoline, salicylic acid, sanguinarine, tannic acid, and zinc pyrithione), together with six conventional antibiotics (ceftriaxone, ciprofloxacin, chloramphenicol, metronidazole, tetracycline, and vancomycin) against CRC-causing pathogens (Clostridium septicum, Esherichia coli, Fusobacterium necrophorum, Fusobacterium nucleatum, Peptostretococcus anaerobius and Streptococcus bovis) using broth-microdilution method assessing minimum inhibitory concentrations (MIC) [4], [5]. Nitroxoline (MICs = 8 – 16 µg/ml), zinc pyrithione (MICs = 4 – 32 µg/ml) and chloroxine (MICs = 4 – 64 µg/ml) have been found to be the most active substances. E. coli and S. bovis were the most susceptible bacteria with MICs ≥ 4 µg/ml. These findings indicate that 8-hydroxyquinoline alkaloids and coordination complexes of zinc are chemical structures with potential to inhibit growth of pathogenic gut microorganisms associated with CRC development. We declare no conflict of interest.

Publication History

Article published online:
12 December 2022

• References

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