Human gut health relevant antibacterial activity of blessed thistle (Cnicus benedictus)

The most common chronic bacterial infection in the human gut is due to Helicobacter pylori, a Gram-negative microaerophilic organism. Infection of H. pylori is commonly associated with many stomach related diseases such as chronic atrophic gastritis, peptic ulceration, and mucosa-associated lymphoid tissue lymphomas. Currently, common synthetic antibiotic treatments for gastritis and peptic ulcer have many harmful side effects and often lead to the development of antibiotic resistance. In this context, extracts of medicinal plants with antimicrobial properties are safe and can be targeted against H pylori infection. Blessed thistle (Cnicus benedictus) is an annual hairy thistle-like plant from the family Asteraceae, and native to the Mediterranean region. Blessed thistle contains lignans, essential oils, tannins, and other bioactive compounds and is used widely in traditional medicines. The objective of this study was to determine anti-bacterial property of aqueous extracts of blessed thistle from three different soil conditions (silty clay loam, sandy loam soil, and slightly saline sandy loam soil) and different maturity stages (H1 = rosette stage, H2 = elongation stage, H3 = 50% flowering stage, H4 = 100% flowering stage and H5 = full mature stage) against pathogenic H. pylori using agar diffusion assay. Furthermore, the one harmful side effect of common synthetic antibiotic drug treatments is the inhibitory activity against beneficial probiotic gut bacteria which leads to diarrhea and other gastrointestinal discomforts. Therefore, the activity of blessed thistle aqueous extracts to support potential proliferation of probiotic gut bacteria such as Bifidobacterium longum was also investigated. Overall, high inhibitory activity (2-5 mm zone inhibition) of aqueous extract of blessed thistle against H. pylori was observed in this study. However, same extract did not have any inhibitory activity against B. longum. Therefore, the findings of this study indicated that blessed thistle is a promising medicinal plant that can be targeted against H. pylori infection and for the potential remedy of related stomach diseases without having any harmful side effects against beneficial gut bacteria.