Less is more: Hormetic and selective antimicrobial activity of a thymoquinone-standardized black seed oil ThymoQuin ® in gut microbiota models

Abstract The gut microbiome plays a central role in host metabolism, immune function, and overall health, with disruptions in microbial composition (dysbiosis) being associated with a range of metabolic, inflammatory, and infectious conditions [1,2]. Consequently, strategies aiming to modulate the microbiome require selective activity that preserves beneficial commensals while limiting pathogenic organisms [3]. In this context, ThymoQuin®—a cold-pressed, standardized black cumin (Nigella sativa) seed oil developed by TriNutra Ltd. and defined by ≥3% thymoquinone (TQ), controlled p-cymene levels, and low free fatty acids (≤1.25%)—was evaluated for its microbiome-relevant activity. In vitro minimum bactericidal concentration (MBC) assays across three independent batches demonstrated a biphasic, dose-dependent response. At intermediate concentrations (0.25–0.5%), Streptococcus thermophilus was strongly stimulated (up to 53-fold) and Lactiplantibacillus plantarum fully preserved, while Klebsiella pneumoniae was effectively reduced (>94%). Akkermansia muciniphila exhibited stable viability at concentrations below 1%, with reductions only observed at 1%. This is notable given its role as a mucin-degrading commensal that has been linked to metabolic health, but whose abundance may vary across physiological and disease contexts [4,5]. At concentrations ≥1%, selective effects diminished, resulting in broader antimicrobial activity and reduced specificity. These findings indicate a defined concentration range in which selective microbiome modulation is maintained, whereas higher thymoquinone levels may increase the risk of non-selective detrimental effect on microbes. Competing Interest Statement The authors have declared no competing interest.