2.4. Soluble sugar and polyols assay
Soluble sugar and polyols in button mushroom were extracted
as described by Tsai et al. (2008). Different dried samples were weighed, ground thoroughly, extracted with 80 mL 50% aqueous
ethanol at 45 C for 40 min, and then filtered through Whatman
No. 4 filter paper. The residues were washed three times, and the
combined filtrates were dried by rotary evaporation and dissolved
in 50% acetonitrile solution to a final volume of 25 mL. The extract
was filtered using a 0.45-lm micro-pore filter membrane prior to
analysis. Each sugar or polyol was identified using a reference compound
(Aladdin Reagent (Shanghai) Co., Ltd, Shanghai, China) and
quantified by the calibration curve of the authentic compound relative
to external standards. The HPLC chromatograms of soluble
sugar and polyols from fresh button mushroom are shown in
Fig. 1A.