Optimized Extraction of Bioactive Polysaccharides from Wild Mushrooms: Toward Enhanced Yield and Antioxidant Activity

The aqueous extraction of bioactive compounds from wild mushroom fruiting bodies, focusing on carbohydrates, has been systematically examined. This study includes three mushroom species common in the northern hemisphere: <i>Suillus luteus</i>, <i>Tricholoma equestre</i>, and <i>Hydnum repandum</i>. These species were selected for their potential as cost-effective sources of bioactive compounds. For each species, the optimization of liquid-to-solid (LS) ratio (50:1 <i>v</i>/<i>w</i> to 150:1 <i>v</i>/<i>w</i>), temperature (70-90 °C), and processing time (3 to 5 h) was conducted to determine optimal parameters for total carbohydrate content (TCC), while minimizing reducing sugars to favor higher molecular weight polysaccharides. The bioactive properties were explored and optimized based on the antioxidant properties of extracts. The data were compared with previous studies on commonly cultivated mushrooms, such as <i>Agaricus bisporus</i>. Results show that the high LS ratio has the most significant influence on TCC content, though optimal values for other parameters (temperature and time) vary by species. The optimal LS ratios were 150:1 for <i>Suillus luteus</i>, 149.89 for <i>Tricholoma equestre</i>, and 149.76 for <i>Hydnum repandum</i>. Temperature and duration varied among species, with <i>Suillus luteus</i> requiring 5 h at 89.92 °C, <i>Tricholoma equestre</i> needing 3.98 h at 70.07 °C, and <i>Hydnum repandum</i> requiring 3.00 h at 70.01 °C. A similar trend was observed in minimizing reducing sugars, confirming the high LS ratio may support extracting longer polysaccharide chains. Studies on antioxidant activity revealed that bioactive molecules in the extract are water-soluble molecules; however, the optimal values for antioxidant activity are strongly mushroom-species-dependent. The optimal conditions for enhancing antioxidant activity of aqueous extracts, measured by ABTS method, were: for <i>Suillus luteus</i>, an LS ratio of 123.68, 5 h, and 86.63 °C; for <i>Tricholoma equestre</i>, an LS ratio of 95.27, 4.05 h, and 73.87 °C; and for <i>Hydnum repandum</i>, an LS ratio of 50.01, 5 h, and 89.98 °C. The aqueous extraction method proved efficient for recovering bioactive polysaccharide fractions from wild mushrooms.