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.
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