Guarana powder polysaccharides: characterisation and evaluation of the antioxidant activity of a pectic fraction.

Guarana is a fruit from the Amazon whose seeds are used to produce guarana powder. Guarana powder is consumed by the population mainly for its stimulant activity. It has been shown that guarana seeds contain low-molar-mass compounds; however, no data have been reported concerning the polysaccharides. In this work, the polysaccharides present in guarana powder were investigated. A pectic fraction and a xylan were isolated and characterised. Antioxidant activity tests were performed with a methanolic extract and the pectic fraction at concentrations of 0.1-10 mg/ml. The methanolic extract exhibited a strong capacity for scavenging DPPH radicals (90.9% at 10 mg/ml). At the same concentration, the polysaccharide showed a DPPH(·)-scavenging activity of 68.4%. At a higher concentration, the methanolic extract and the polysaccharide exhibited similar hydroxyl radical-scavenging effects (~70%). The results suggest that the polysaccharides present in guarana can contribute to the possible biological effects of guarana powder.