Assessment of the potential health-promoting effects of oat flour and husks on gut microbiota

Introduction: Oats are gluten-free grains abundant in dietary fiber, β-glucans, phenolic acids, flavonoids, carotenoids, vitamin E, and phytosterols. Traditional medicine has used them for millennia to treat hyperacidity, severe pancreatitis, burns, and dermal irritation. Oat β-glucans are a type of soluble fiber that gut bacteria break down in the colon, leading to the production of short-chain fatty acids. Additionally, oat β-glucans act as a prebiotic that helps balance gut microbiota and supports the control of diarrhea and related issues by keeping energy levels stable, thanks to its properties such as solubility, thickening, and ability to form gels. Human digestive enzymes and stomach acid break down only small portions of oat β-glucan; instead, it moves to the large intestine, where gut bacteria break it down. Phenolic acids offer prospective health benefits and enhance gut health by promoting the proliferation of beneficial bacteria and inhibiting pathogens, thereby supporting overall digestive health. Experimental: This study investigated the nutritional and phenolic content of oat flour (OF) and powdered oat husks (OHs) from different oat genotypes—white, brown, and black—as well as their antioxidant capacity. Standard laboratory, spectrophotometric and HPLC methods were applied. Antimicrobial activity evaluation was conducted on oat extracts prepared according to a recipe from traditional Serbian medicine and by conventional alkaline hydrolysis and extraction. The antimicrobial effect of oat samples was tested on six important pathogens of the gastrointestinal tract, namely Listeria monocytogenes, Staphylococcus haemolyticus, Salmonella typhimurium, Enterococcus faecalis, Escherichia coli, and Shigella flexneri. The minimal bactericidal concentration (MBC) of hydrolyzed and traditionally prepared oat extracts was determined and expressed in microliters of the preparation. Key findings: OF samples exhibited, on average, high protein content (15.83%), fat content (6.27%), and β-glucan content (4.69%), whereas OH samples were abundant in dietary fiber. OHs exhibited total insoluble-bound phenolic compound levels that were 13 to 25 times higher than in the OFs. These bioactive compounds may enhance the pronounced antioxidant and antibacterial activity detected in the extracts. Ferulic acid was the most prevalent in all samples, succeeded by p-coumaric, isoferulic, vanillic, and syringic acid. The samples obtained by hydrolysis showed a higher bactericidal activity, which can be associated with a higher content of polyphenols. The traditionally prepared OH extracts had the highest bactericidal effect on Listeria monocytogenes, Escherichia coli, and Staphylococcus haemolyticus, while Salmonella typhimurium was the least affected by the bactericidal effects of all the samples tested. These findings underscore the potential of both OF and powdered OHs for application as functional food ingredients and nutraceuticals due to their beneficial nutritional composition and potential health effects, which could offer numerous health benefits, such as better gut health, less oxidative stress, and stronger immunity. More studies are needed to fully understand how these benefits work and to improve the ways we extract and create oat-based products.