Effects of extraction temperature on efficacy of lingzhi or reishi medicinal mushroom, ganoderma lucidum (Agaricomycetes), aqueous extract against oxidative stress

This study was designed to understand the effect of extraction temperature, i.e., room temperature (GL_RT), 50°C (GL₅₀), 100°C (hot water; GL₁₀₀), and 200°C (GL₂₀₀) on antioxidant and biological activity of G. lucidum. The % yield obtained was 5.3%, 7.6%, 10.7%, and 13.2% at various extraction temperatures; room temperature, 50°C, 100°C and 200°C, respectively. Similarly, phenolic content (51.6, 57.9, 82.9, and 93.1 mg/g extract) and flavonoid content (18.8, 23.2, 34.3, and 36.3 mg/g extract) were observed to be increased with rise in extraction temperature. However, extraction temperature resulted in loss of antioxidant activities above 100°C as evident by chemical assays such as DPPH, FRAP, ABTS, and TRP conducted on extracts. In contrast, three bioactive compounds, i.e., adenine (3.26, 3.48, 2.16, and 1.45 mg/g extract), uracil (3.99, 3.21, 2.51, and 1.47 mg/g extract), and adenosine (5.92, 5.62, 2.22 and 0.7 mg/g extract), quantified by high performance thin layer chromatography showed decrease in their content with increasing extraction temperature. Extract prepared at room temperature and 50°C prevented loss of cell viability and generation of reactive oxygen species resulted after hydrogen peroxide exposure; however, cytoprotective efficacy was not significant at 100°C and 200°C_. The order of cytoprotective effects observed by these extract were in the following order: room temperature ≥ 50°C > 100°C > 200°C. Overall, the optimal temperature conditions for the efficient extraction of G. lucidum with water retaining bioactive compounds and biological activity was found to be below 100°C.