Interaction between Gut Microbiota and Curcumin: A New Key of Understanding for the Health Effects of Curcumin

Abstract

Curcumin, a lipophilic polyphenol contained in the rhizome of Curcuma longa (turmeric), has been used for centuries in traditional Asian medicine, and nowadays it is widely used in food as dietary spice worldwide. It has received considerable attention for its pharmacological activities, which appear to act primarily through anti-inflammatory and antioxidant mechanisms. For this reason, it has been proposed as a tool for the management of many diseases, among which are gastrointestinal and neurological diseases, diabetes, and several types of cancer. However, the pharmacology of curcumin remains to be elucidated; indeed, a discrepancy exists between the well-documented in vitro and in vivo activities of curcumin and its poor bioavailability and chemical instability that should limit any therapeutic effect. Recently, it has been hypothesized that curcumin could exert direct regulative effects primarily in the gastrointestinal tract, where high concentrations of this polyphenol have been detected after oral administration. Consequently, it might be hypothesized that curcumin directly exerts its regulatory effects on the gut microbiota, thus explaining the paradox between its low systemic bioavailability and its wide pharmacological activities. It is well known that the microbiota has several important roles in human physiology, and its composition can be influenced by a multitude of environmental and lifestyle factors. Accordingly, any perturbations in gut microbiome profile or dysbiosis can have a key role in human disease progression. Interestingly, curcumin and its metabolites have been shown to influence the microbiota. It is worth noting that from the interaction between curcumin and microbiota two different phenomena arise: the regulation of intestinal microflora by curcumin and the biotransformation of curcumin by gut microbiota, both of them potentially crucial for curcumin activity. This review summarizes the most recent studies on this topic, highlighting the strong connection between curcumin and gut microbiota, with the final aim of adding new insight into the potential mechanisms by which curcumin exerts its effects.

The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota

“…It is supposed that curcumin passes through the stomach without any chemical modifications and reaches the large intestine, where it undergoes extensive phase I and II metabolism. The reductive pathways of metabolism by phase I enzymes lead to the formation of dihydrocurcumin, tetrahydrocurcumin, and hexahydrocurcumin ( Figure 20 ) [ 325 ].…”

“…All these metabolites can undergo phase II metabolism by glucuronidases and sulfotransferases that are capable of conjugating glucuronic acid or sulfate molecule, respectively, to produce the corresponding glucuronide and sulfate O-conjugated metabolites. Furthermore, gut microbiota may deconjugate the phase II metabolites and convert them back to the corresponding phase I metabolites or to fission products such as ferulic acid and dihydroferulic acid in the colon [ 325 ].…”

Curcumin, Quercetin, Catechins and Metabolic Diseases: The Role of Gut Microbiota

“…Transformation not only occurs through enzymes produced by hepatocytes or enterocytes, but also by the enzymes of GM residing in the colon, which can generate many active metabolites [ 104 ]. Curcumin metabolites have properties and potency similar to curcumin and exhibit the same physiological and pharmacological properties [ 105 ]. It has been stated that curcumin and GM have bidirectional interactions such as GM regulation by curcumin and biotransformation of curcumin by GM [ 101 , 105 , 106 ].…”

“…Curcumin metabolites have properties and potency similar to curcumin and exhibit the same physiological and pharmacological properties [ 105 ]. It has been stated that curcumin and GM have bidirectional interactions such as GM regulation by curcumin and biotransformation of curcumin by GM [ 101 , 105 , 106 ]. The reciprocal interaction between curcumin and GM is illustrated in Figure 3 .…”

Experimental Therapeutics for the Treatment of Osteoarthritis

“…LPS might accumulate in response to microbiome imbalance (dysbiosis) and present a link by mediating low-grade inflammation between obesity and metabolic syndrome. 55 In this regard, the biotransformation of curcumin, for example, by gut microbiota might explain its beneficial health effects 138 and this important mechanism might also influence other compounds. Therefore, this interrelation has to be addressed in more detail in future.…”