Preparation of substrates from SCG was done according to Chaa
et al. (2008), it involves five steps. The first step consists to treat
20 g of SCG in a mixture of chloroform and methanol (150/150 v/
v) for 14 h, then in pure ethanol for 2 h and finally in boiling ethanol
for 2 h. In the second step, the obtained insoluble residue was
treated in boiling distilled water for 4 h, and finally in 1% EDTA pH
6.8 at 80 C for 4 h. The next step, the insoluble residue was treated
in 1% NaOH prepared in 70% ethanol at 80 C for 2 h. Finally the last
step consisted to treat the insoluble residue with 14% KOH for 14 h
at room temperature. After each step, the insoluble residue was
washed several times with distilled water, dried at 70 C and a
sample (1 g) was conserved for further analysis. The collected substrates
received codes from S1 to S5.