Objective: The main study was to evaluate the anti- inflammatory, anti-oxidant, and the gastro-protective properties of extracts of Stevia rebaudiana. In addition the purpose of the study was to investigate new, natural inhibition of urease and xanthine oxidase enzymes, as well as to find the sugar contents of extracts from the plants.
Method: The polyphenolic contents of methanol extracted samples were evaluated in three different ways: total phenolic contents, total flavonoid content and condensed tannin. The antioxidant activity was determined using ferric reducing antioxidant power and using the free radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl radicals and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) tests. Phenolic compounds were determined by high-performance liquid chromatography.
Results: Results of antioxidant activity gave a total pheneolic content of 12.303-8.477 mg/g gallic acid equivalent, total flavonoid content of 2.378-1.518 mg/g quercetin equivalent and condense tanin of 3.435-0.713 mg/g catechin equivalent in leaf and flower extracts. Ferric reducing antioxidant power values of the Stevia rebaudiana leaf and flower were discovered to be 202.499-116.826 M FeSO47H2O/g respectively. The radical scavenging activity values of the 2,2- diphenyl-1-picrylhydrazyl radical and the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) tests ranged between 0.533-0.398 and 6.637-17.382 mg/mL respectively. The inhibitory effect of the Stevia leaf extract on xanthine oxidase and urease was also investigated and the concentrations that gave 50% inhibition of maximal activity were found to be 23.51g/mL and 9.45g/mL respectively. Glucose and fructose were determined to be the sugars in the Stevia leaf.
Conclusion: The results indicate that the Stevia rebaudiana plant is not only rich in steviol glycosides, but is also a powerful natural antioxidant and anti-inflammatory with gastro-protective properties.
Keywords: Antioxidant, radical, phenolics compound, xanthine oxidase, urease.