Abstract
The use of food additives with xanthine oxidase (XO) inhibitory activity offers an alternative approach to hyperuricemic and gout disease treatment, and provides an example of antioxidant nutraceutics. The in vitro and in silico XO inhibitory activity of polyphenols from Uruguayan Tannat grape pomaces and propolis extracts was evaluated as well as the scavenging capacity of said compounds. When comparing propolis and grape pomace samples, the in vitro studies demonstrated that polyphenols extracted from propolis are more active as free radical scavengers than those from Tannat grape pomace. Both natural products effectively inhibited XO but the capacity of phenols present in GP is higher than the one present in P. The high content of anthocyanins in GP, absent in P, could account for this observation. In silico assays allowed us to determine relevant ligand-receptor interactions between polyphenols, from a database built with previously reported polyphenols from both natural products, and the active site of XO. The in silico results showed that compound (E)-isoprenylcaffeate from propolis was the best potential XO inhibitor displaying hydrophobic aromatic interaction between the conjugated ring of the caffeate moiety and polar interactions between hydroxyl groups from caffeate with the active site polar residues. Among grape pomaces, the Cyanidin-3-O-(6-(E)-p-coumaroyl)-glucoside was the best XO inhibitor; its moiety oxychromenyl being relevant to the docking stabilization. All these results lead us to propose Uruguayan propolis and Tannat grape pomace extracts as food additives as well as phytopharmaceuticals to decrease the uric acid levels in gout disease and to act against oxidative stress.
Highlights
Xanthine oxidase (XO) participates in purine catabolism, generating uric acid as a final product and the release of reactive oxygen species (ROS) such as O 2− and H2O2
We studied the total phenolic contents, the scavenging activity and, for the first time, the in vitro xanthine oxidase (XO) inhibitory activity of polyphenolic rich extracts from Uruguayan propolis and Tannat grape pomace
We were able to prove that the Uruguayan P and Tannat Grape pomaces (GP) extracts can act as free radical scavengers, with samples of propolis being significantly more active than those of grape pomaces
Summary
Xanthine oxidase (XO) participates in purine catabolism, generating uric acid as a final product and the release of reactive oxygen species (ROS) such as O 2− and H2O2. Current gout treatments are palliative at the level of pain and chronic inflammation, and treatments involving xanthine oxidase inhibitors are available, serious adverse effects have been reported [8]. In this context, natural products represent an important alternative. Antioxidant, antimicrobial, antimutagenic, anticarcinogenic and antilipogenic activities have been reported for GP [17] [18] Both P and GP, have been described as important sources of bioactive compounds, most of them polyphenols [17] [19] [20] [21] [22]. In silico assays were performed in an attempt to account for the molecular basis of the interaction between the enzyme and polyphenols-like compounds, present in the extracts according to previous reports [23] [24]
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