Abstract
A novel polysaccharide (LCP50S-2) with antioxidant activity was isolated from Litchi chinensis Sonn. The structure of LCP50S-2 was elucidated on the basis of physicochemical and instrumental analyses, and its average molecular weight was determined by gel permeation chromatography to be 2.19 × 10(2) kDa. The backbone of LCP50S-2 was composed of (1→3)-linked β-L-rhamnopyranosyl residues, (1→4)-linked α-D-xylopyranosyl residues, (1→4)-linked β-D-glucopyranosyl residues, and (1→4)-linked α-D-glucopyranosyl residues which branched at O-6. The two branches consisted of α-L-arabinopyranosyl residues and (1→6)-linked β-D-galactopyranosyl residues terminated with α-L-arabinopyranosyl residues, respectively. In the in vitro antioxidant assay, LCP50S-2 was found to possess DPPH radical-scavenging activity and hydroxyl radical-scavenging activity with IC(50) values of 220 and 266 μg/mL, respectively.
Introduction
Oxidation is an essential process for all living organisms for the production of energy necessary for biological processes.(1, 2) However, the uncontrolled production of oxygen-derived free radicals is responsible for many diseases such as cancer, rheumatoid arthritis, and atherosclerosis, as well as degenerative processes associated with aging.(3) It has also been reported that reactive oxygen species (ROS) are capable of damaging DNA, which has been associated with cancer, coronary heart diseases, and many other age-related health problems.(4) Thus, there has been increasing interest in finding natural, effective, and safe antioxidants to protect the human body from free radicals and prevent the onset of chronic diseases.(5, 6) Pharmacological antioxidant activities are generally achieved in two ways, one by scavenging ROS and the other by inhibiting the generation of ROS. Synthetic antioxidants are currently being used for industrial processing to preserve food quality. Published data indicate that some plant polysaccharides have strong antioxidant activities and could be developed into drugs.(7-9) The antioxidants present in plants are of great interest as potential protective agents against oxidative damage. For instance, polysaccharides extracted from fruit bodies of Auricularia auricular were shown to possess antioxidant properties by their free radical-scavenging abilities and could be developed into health food.(10)
Litchi (Litchi chinensis Sonn.), a tropical fruit native to China, is cultivated in many parts of the world having a warm climate.(11-16) Litchi fruit pericarp tissues contain a large number of polysaccharides and proteins. Kong et al. reported that three fractions of water-soluble polysaccharide fractions, coded LFP1, LFP2, and LFP3, were isolated and purified from litchi pulp. The antioxidant activities of these fractions were investigated using various in vitro assay systems. Results indicated that LFP3 showed the highest antioxidant activity among the three fractions of polysaccharides and could be explored as a novel potential antioxidant.(2, 12) However, to date, little is known about the fine structural elucidation and antioxidant activities of litchi pulp polysaccharides.
Detailed characterizations of these polysaccharides are critical to a better understanding of the structural and functional properties of these substances for future nutritional and therapeutic applications. Here, we present the first detailed study of the polysaccharide structure of L. chinensis pulp tissues. In this study, we report the extraction, purification, and detailed structures of a novel polysaccharide (LCP50S-2) from the pulp tissues of L. chinensis using DEAE-52 cellulose column chromatography and DEAE-Sepharose Fast Flow column chromatography, as well as physicochemical properties and instrumental analyses. In particular, the in vitro antioxidant activity of LCP50S-2 was also assayed and established.
