In vitro growth-inhibitory effect of plant extracts and alkaloids against diarrheal and probiotic bacteria

Bc. Anna Wildová

Master's thesis

Abstract:

Although symptom diarrhoea is treatable and preventable, every year more than 1.5 million people die from diarrhoeal diseases. The most common bacteria causing-diarrhoea are Shigella (low and middle-income countries) and Salmonella (developed countries). When the bacterial diarrhoea is diagnosed, generally causal treatment in form of antibiotics is applicated. The widespread misuse of antibiotics has contributed to the development of resistance in bacterial strains to the drugs. According to ethnobotanical, chemotaxonomic and structure-activity relationships (SARs) data, five alkaloids and six plant extracts were selected and tested for their antimicrobial effects by broth microdilution method. Two of five alkaloids chelerythrine and 6,6’-dihydroxythiobinupharidine produced growth-inhibitory activity against various pathogenic diarrhoeal bacteria. MIC values of chelerythrine against B. cereus, C. perfringens, E. coli, L. monocytogenes and Y. enterocollica were 8, 64, 128, 32 and 128 μg/mL, respectively. 6,6´-Dihydroxythiobinupharidine inhibited B. cereus, C. perfringens, E. faecalis and Y. enterocollica with slightly higher respective MICs of 64, 128, 256 and 256 μg/mL than chelerythrine. Of the six plant extracts tested, only M. pteleifolia showed antibacterial activity against C. perfringens with MIC = 512 μg/mL. Nevertheless, both chelerythrine and 6,6´-dihydroxythiobinupharidine were more toxic to beneficial than to diarrheal bacteria. Antibiotic ciprofloxacin produced selective antibacterial effect and inhibited growth of all pathogenic strains. To the best of our knowledge, the activity of tested plant extracts and alkaloids against various diarrhoeal and probiotic bacteria have been tested for the first time.

Keywords

alkaloids, plant extracts, growth-inhibitory effects, chemotaxonomy, diarrheal bacteria, probiotic bacteria

Language used: English

Date on which the thesis was submitted / produced: 28. 4. 2024

Thesis defence

• Date of defence: 3. 6. 2024
• Supervisor: prof. Ing. Ladislav Kokoška, Ph.D.
• Reader: Yaakov Gopes, externi

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme:
Tropical Crop Management and Ecology