Amino Acids from Ganoderma lucidum: Extraction Optimization, Composition Analysis, Hypoglycemic and Antioxidant Activities

Background: Ganoderma lucidum is a well-known edible mushroom and traditional Chinese medicine, but there were no comprehensive reports on the extraction, analysis and activities test of Ganoderma lucidum Amino Acids (GLAA). Objective: The present study was aimed to optimize the extraction process of GLAA and analyze the amino acid composition of GLAA, combined with preliminary activity evaluation. Methods: The hydrochloric acid-hydrolysis method for extraction of GLAA was optimized by Response Surface Methodology (RSM) with Box-Behnken Design (BBD). The amino acid composition of GLAA was analyzed by PITC pre-column derivation with HPLC method and amino acid automatic analyzer. The hypoglycemic and antioxidant activities of GLAA were assayed by inhibitory rate of α- glucosidase and DPPH radical scavenging rate, respectively. Results: The optimal extraction conditions were obtained: liquid-to-solid ratio 20:1 mL/g, extraction time 9.5 h, hydrochloric acid concentration 7.0 mol/L, and the yield of GLAA was 4.78 ± 0.21 %. The result of amino acid automatic analyzer showed that the content of total amino acids in GLAA was 2.94 %, including 18 kinds of amino acids, and the most abundant amino acid was leucine (0.37 %). The results of activity tests in vitro showed that GLAA exhibited high α-glucosidase inhibitory rate with IC50 value of 380.62 μg/mL and a certain scavenging DPPH activity with IC50 of 484.54 μg/mL. Conclusion: The RSM with BBD was successfully implemented for optimization of the extraction parameters of GLAA. The GLAA was rich in 18 kinds of amino acids and possessed strong hypoglycemic and antioxidant activities.