Effect of Tween 80 and Acetone on the Secretion, Structure and Antioxidant Activities of Exopolysaccharides from Lentinus tigrinus

Abstract

In this study, the effects of the addition of Tween 80 and acetone on secretion, structure and antioxidant activities of Lentinus tigrinus exopolysaccharides (EPS) were investigated. It was found that Tween 80 and acetone displayed a stimulatory effect on EPS secretion. The EPS obtained by the addition of Tween 80 (EPS-T), acetone (EPS-A) and control (EPS--C) were purified by Sepharose CL-6B gel filtration chromatography and molecular mass of purified fractions was estimated to be 22.1, 137 and 12 kDa, respectively. Monosaccharide composition analysis indicated that EPS-T, EPS-A and EPS-C were mainly composed of glucose and mannose. Congo Red test indicated that EPS-T and EPS-A had a highly ordered conformation of triple helix, while EPS-C had a random coil conformation. Furthermore, EPS-A exhibited higher DPPH scavenging and antiproliferative activities than EPS--C and EPS-T, which might be attributed to the molecular mass.

Keywords: Lentinus tigrinus; antiproliferative activity; exopolysaccharides; molecular conformation; molecular mass.

Fig. 1

The results of: a) size-exclusion chromatography in Sepharose CL-6B column, and b) the FTIR spectra of the exopolysaccharides (EPS) produced by submerged culture of Lentinus tigrinus using Tween 80 (EPS-T) and acetone (EPS-A), in comparison with control (EPS-C). V(sample)=5 mL

Fig. 2

Molecular mass of the purified exopolysaccharides (EPS, closed circles) produced by submerged culture of Lentinus tigrinus using Tween 80 (EPS-T) and acetone (EPS-A), in comparison with control without the addition of stimulating agents (EPS-C), on Sepharose CL-6B column. Elutes were analyzed by measuring the absorbance at 490 nm (A_{490 nm}). Open circles represent different dextrans used as control. K_av=partition coefficient

Fig. 3

The results of Congo Red test of exopolysaccharides (EPS, closed circles) produced by submerged culture of L. tigrinus using: a) Tween 80 (EPS-T), b) acetone (EPS-A), and c) control without the addition of stimulating agents (EPS-C), presented as wavelength of absorption maxima of the complex of Congo Red with polysaccharide at various concentrations of NaOH. Congo Red in NaOH and dextran served as standards (open circles)

Fig. 4

Bioactivity of exopolysaccharides (EPS) produced by submerged culture of Lentinus tigrinus using Tween 80 (EPS-T, triangle) and acetone (EPS-A, closed circle). The results represent mean value± S.D. (N=3): a) OH and b) DPPH radical scavenging activity and antiproliferative activity against: c) Hep G2, and d) MG-63 cells, in comparison with control (EPS-C, open circle). Cells were grown on 96--well plates and allowed to attach for 16 h, and cell viability was determined by MTT assay