The anti-oxidative effect of Lingzhi protein hydrolysates on lipopolysaccharide-stimulated A549 cells

Abstract

Lingzhi (Ganoderma lucidum) is an oriental fungus used as a traditional Chinese medicine. To study the distribution of protein of Lingzhi, synchrotron radiation based FTIR was chosen to identify a rich-protein region. Lingzhi was subsequently hydrolyzed with pepsin followed by trypsin to obtain hydrolysates and purified using an ultrafiltration (3 kDa cut-off) and a C18-SPE column. The hydrolysates were chosen to study in vitro antioxidative ability and the protective effect against oxidative stress, as well as label-free quantification proteomics in A549 cells induced with LPS. FTIR showed protein content in the cap was higher than the stem. The antioxidative abilities of the cap hydrolysates were measured using DPPH, ABTS, and FRAP had 0.14 ± 0.02 mg ascorbic acid, 0.11 ± 0.03 mg gallic acid, and 3.25 mM FeSO4, respectively. The protective effect of the hydrolysates showed the reduction of lipid peroxidation by 54 ± 2% compared to the control. Proteomics analysis identified 262 proteins. Among these proteins, 4 proteins were only found in the treatment group. These proteins were in protein transport, glycolysis, plasminogen activation, transcription regulation, keratinocyte development, and angiogenesis. In addition, proteins at ~2 fold greater amounts than the control were associated with RNA helicase. Western blot analysis of SOD1, a detoxification enzyme for oxidative stress, implied a slightly elevated SOD1 expression in LPS-stimulated A549 cells. This information could lead to a better understanding of the anti-oxidative effect of Lingzhi protein hydrolysates and supported their potential use as a functional food ingredient with anti-oxidative stress activities.