From Phenolic Profile to Gut Function: Comparative Effects of Region-Specific Shilajit on Selected Culturable Intestinal Microbial Groups and β-Glucuronidase Activity—A Preliminary Study

Shilajit is a complex natural phytomineral substance whose composition and biological activity may vary depending on geographical origin. This study compared three commercially available Shilajit samples from Russia (S1), Nepal (S2), and Iran (S3) in terms of phenolic acid profile, antimicrobial activity, and their effects on selected intestinal microorganisms and β-glucuronidase activity after simulated gastrointestinal digestion. The samples differed markedly in their phenolic composition, with S3 showing the highest total content of the quantified phenolic acids. All samples exhibited antimicrobial activity, although their intensity depended on the microorganism tested. The in vitro digestion model revealed clear sample-dependent effects: S2 showed the lowest net β-glucuronidase activity and the most beneficial modulation of Lactobacillus and Bifidobacterium, whereas S1 exerted the strongest suppressive effect on Escherichia coli. In contrast, S3, despite the richest phenolic profile, showed the highest β-glucuronidase activity. These findings indicate that the biological activity of Shilajit depends not only on the quantified phenolic acids but also on the broader, region-specific chemical matrix of the material.