Isolation of chemical compositions as dietary antioxidant supplements and neuroprotectants from Chaga mushroom (Inonotus obliquus)

Excessive free radicals can cause oxidative stress (OS), which lead to neurodegenerative diseases (ND) are harmful to the human body. Therefore, it is necessary to explore dietary antioxidants and neuroprotectants from nutrient foods. Chaga mushroom (Inonotus obliquus) has been used as an important functional food in many countries for centuries. This present study was carried out to discover active compounds from I. obliquus and investigate the in vitro antioxidant activity and neuroprotective activity. Sixteen natural products including two new isocoumarins (1–2), a new 8-O-4′-neolignan (3), a new cyclic diarylheptanoid (4), and twelve known compounds (5–16) were separated from I. obliquus. Their structures were elucidated by extensive spectroscopic analyses of high resolution electrospray mass spectrometry (HRESIMS), ultra violet (UV), and nuclear magnetic resonance (NMR). Among them, compounds 1 and 2 revealed remarkable antioxidant activities through the comprehensive analysis of DPPH, ABTS, and ferric reducing antioxidant power (FRAP) methods. Meanwhile, compound 1 demonstrated significant neuroprotective activity by increasing SH-SY5Y cells viability and preventing mitochondrial damage. Apart from that, electronic analyses were performed using the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) to analyze compound 1. These results indicated that compound 1 had a significant implication for the search of natural raw material to prevent OS and nerve damage in the field of functional foods, and the isocoumarin fragment as well as an oxygenated cis double-bond might be the active sites to play prominent parts in antioxidant and neuroprotective activities of compound 1.