Antioxidation and immune-stimulatory actions of cold alkali extracted polysaccharide fraction from Macrocybe lobayensis , a wild edible mushroom.

Mushroom β-glucans are presently gaining widespread attention, being one of the promising healthy compounds with excellent antioxidative and immunomodulatory activities. Conventionally, hot water extraction procedure is followed to isolate the polymers where the residue is discarded after filtration. However, the remnants still contain plenty of bioactive components that could provide a unique opportunity for the discovery of novel therapeutic agents. In this backdrop, the present study was aimed to expand utilization of a popularly edible mushroom, Macrocybe lobayensis , by re-cycling left-over material that has passed through traditional aqueous process. For that, the residue was immersed in alkaline solution followed by ethanol precipitation and repeated washing resulting preparation of a water soluble and partially purified polysaccharidic fraction (ML-CAP). Chemical and molecular characterization by FT-IR, HPTLC, GC-MS, GPC and spectroscopy unveiled that ML-CAP was consisted of a homo-polymer with Mw of ~ 122 kDa. The backbone was mainly composed of β-glucan where galactose was identified as the second most abundant unit. Subsequently, the fraction exhibited potent antioxidant activity in terms of radical scavenging, chelating ability and reducing power. Furthermore, strong immune enhancing property was also recorded as the polymer, particularly at the concentration of 100 µg/ml, triggered murine macrophage functionality in terms of cell proliferation, phagocytosis, pseudopods formation and nitric oxide production. The study thus advocates for potential application and further extraction of hot water extracted mushroom residue in drug development and nutraceutical industries, as the example of ML-CAP showed promising biological effects.