Extraction and in vitro antioxidant activity of polysaccharides from Rubus cochinchinensis

Abstract

Rubus cochinchinensis Tratt. is a traditional medicinal plant in Vietnam and has long been used in folk medicine to treat rheumatism, hematoma, hepatitis, and jaundice. However, studies on this plant’s antioxidant activity and polysaccharide extraction procedures remain limited. This study aims to determine the optimal conditions for polysaccharide extraction from R. cochinchinensis and evaluate its antioxidant potential. The optimal extraction conditions were found to be as follows: a temperature of 100 °C, an extraction time of 3 hours, water as the extraction solvent at a solvent-to-material ratio of 50:1 (v/w), three extraction cycles, and an ethanol-to-extract ratio of 4:1 (v/v) for polysaccharide precipitation. The structural characterisation of the extracted polysaccharides was conducted by using Fourier-transform infrared spectroscopy (FT-IR) and gel permeation chromatography. The polysaccharides exhibited an average molecular weight of approximately 510.87 kDa, with a polydispersity index (Mw/Mn) of 27.66. FT-IR analysis revealed characteristic absorption bands corresponding to glucose and galactose residues. In vitro antioxidant assays demonstrated significant activity, with a total antioxidant capacity reaching 0.2793 ± 0.0019 mg GAE/g or 0.1811 ± 0.0009 mg ASE/g. The IC₅₀ values for DPPH and ABTS radical scavenging were 0.87 mg/mL and 3.26 mg/mL, respectively. These findings suggest that polysaccharides extracted from R. cochinchinensis possess promising antioxidant properties and warrant further investigation for potential applications.