Xiao, HangMcclements, DavidGibbons, JohnLiu, ZhenhuaLuo, Minna2025-04-072025-04-072025-0210.7275/56011https://hdl.handle.net/20.500.14394/56011Curcumin, derived from the rhizome of turmeric plant (Curcuma longa) rhizome, has been used in traditional Asian medicine for its therapeutic benefits for centuries. Extensive research has shown that curcumin acts on various cellular signaling pathways, and this has been related to its potential to treat a range of disorders. Early clinical trials have demonstrated its promising role in preventing colon, oral cavity, and liver cancers. However, the plasma concentrations of curcumin required for effectiveness are much higher than what can be achieved in current settings. This is due to the hydrophobic nature of curcumin, which results in low plasma levels and poor bioavailability. Therefore, there is a paradox between the high bioavailability and low bioavailability of curcumin. To explain, recent studies noticed that curcumin could affect gut microbiota composition, increasing gut microbiota diversity and beneficial commensal bacteria, and decreasing potentially pathogenic bacteria. Therefore, it was hypothesized that gut microbiota might be the potential target for curcumin’s therapeutic effects. However, the interaction between gut microbiota and curcumin is not sufficient and requires more studies. Therefore, the goal of this research is to enhance our understanding of the interactions between curcumin and gut microbiota and to discover and identify gut microbiota capable of metabolizing curcumin and gut microbiota-derived metabolites. First, the role of gut microbiota in curcumin metabolism in vivo remains poorly understood. To address this, we used antibiotics to deplete gut microbiota and compared curcumin metabolism in control and antibiotic-treated mice. Using Q-TOF and triple quadrupole mass spectrometry, we identified and quantified curcumin metabolites, revealing distinct metabolic pathways in these two mice groups. The novel metabolites, hexahydro-dimethyl-curcumin and hexahydro-didemethyl-curcumin were exclusively derived from gut microbiota. Additionally, gut bacteria deconjugated curcumin metabolites back into their bioactive forms. Moreover, control mice exhibited significantly lower curcumin degradation, suggesting a protective role of gut microbiota against degradation. In conclusion, these results indicated that gut microbiota might enhance the effectiveness of curcumin by deconjugation, production of active metabolites, and protection against degradation in the large intestine. Second, interindividual variation in this process remains unexplored. In this study, we anaerobically fermented curcumin with gut microbiota from seven donors in vitro. Curcumin metabolites were qualified and quantified using UPLC-orbitrap fusion tribrid mass spectrometer and LC-MS, respectively. Sixteen metabolites were identified, with methylated and acetylated metabolites being reported for the first time. Tautomers of five compounds were also identified, predominantly in enol forms. Quantification of these metabolites in different human fecal samples over time revealed significant variations in the types and levels of curcumin metabolites produced among individuals. These differences are attributed to variations in gut microbial profiles based on 16S rRNA sequencing results. Significant correlations were found between specific bacterial taxa and curcumin metabolites. In summary, our study identified new metabolites of curcumin and highlighted significant interindividual differences in the capacity of gut bacteria to metabolize curcumin. Lastly, although curcumin is widely recognized for its health benefits, the role of gut microbiota in its metabolic transformation was not well-studied. In this study, bacterial strains capable of metabolizing curcumin were isolated from human stool samples. Using 16S rRNA and whole-genome sequencing, two novel strains (Clostridium butyricum UMA_cur1 and Escherichia coli UMA_cur2) were identified. In addition, the metabolic products were analyzed using liquid chromatography-mass spectrometry (LC-MS). These strains efficiently converted curcumin into dihydro-curcumin (DHC) and tetrahydro-curcumin (THC). Notably, E. coli UMA_cur2 also produced hexahydro-curcumin (HHC) and octahydro-curcumin (OHC), marking the first identification of a strain capable of such transformations. The absence of the YncB gene (typically involved in curcumin conversion) in C. butyricum UMA_cur1 suggests an alternative metabolic pathway. Curcumin metabolism begins during the stationary growth phase, indicating that it is not crucial for primary growth functions. Furthermore, E. coli UMA_cur2 produced these metabolites sequentially, starting with DHC and THC and progressing to HHC and OHC. These findings identified two novel strains that can metabolize curcumin to hydrogenated metabolites. In conclusion, these studies improve our understanding of the interactions between curcumin and gut microbiota.en-USAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/Curcumingut microbiotademethylationantibioticshydrogenated metabolitesmass spectracorrelationtautomerinterindividual variationcurcuminoidsconversiongut bacteriaClostridium butyricumEscherichia coli.Dissertation (Open Access)https://orcid.org/0009-0006-9610-3937