Amino acid analysis
The dried ground samples (100 mg) were hydrolyzed with 6 N HCl (10 ml) in a sealed tube at 110°C for 24 h. The excess of HCl was then freed from 1 ml hydrolyzed under vacuum with occasionally addition of distilled water, then evaporated to dryness. The HCl free residue was dissolved in 2 ml of diluting buffer (0.2M, pH 2.2). Amino acid quantities were determined by using automatic amino acid analyzer AAA 400 INGOS Ltd (Block et al., 1958)