Comprehensive characterization of shilajit from varied provenance: elemental profile, urolithin A content, and antimicrobial activity

Shilajit is an exudate rich in humic substances that collected from rocks in several mountain ranges and has been used for centuries in traditional medicine for fatigue, physical performance, and general vitality. Ten shilajit samples from five mountain regions (Himalayas, Andes, Altai, Caucasus, and Carpathians) were assessed by differential scanning calorimetry (DSC), elemental composition by inductively coupled plasma mass spectrometry (ICP-MS), urolithin A (Uro-A) content by liquid chromatography–tandem mass spectrometry (LC-MS/MS), and antimicrobial activity by broth microdilution against five bacterial and five fungal species. DSC identified two distinct thermal groups: seven samples showed only melting transitions between 100–159 °C, while three samples exhibited low-temperature crystallization and sub-zero melting. ICP-MS revealed potassium as the dominant macroelement (up to ~95,600 ppm), with essential trace elements (selenium, zinc and iron) and toxic elements [arsenic (0.14–1.34 ppm), cadmium (0.01–0.10 ppm) and lead (0.35–3.01 ppm)] all present at levels well within FDA/WHO tolerable intake thresholds, comparable to background levels reported in common foods such as dark chocolate. Uro-A content was strongly solvent-dependent, ranging from 0.07 to 1.63 ppm in methanol to 3.46–58.46 ppm in a methanol/ethyl acetate mixture. Antimicrobial activity was species-dependent (MIC 3.12–25 mg/mL), limited to Bacillus subtilis and Staphylococcus aureus and only two fungal strains ( Mucor mucedo and Geotrichum candidum ), with no activity against the Escherichia coli and Proteus mirabilis . These findings support shilajit’s compositional diversity and highlight Uro-A as its most promising bioactive component, warranting further standardization and origin-based sourcing studies for future bioavailability studies for the potential use as a functional food ingredient.