Antioxidant Response Element Induction and Anti-skeletal Muscle Atrophic Activity of Isocoumarins from Eupolyphaga sinensis

Eupolyphaga sinensis Walker, belonging to the family Corydiidae (Blattodea), is common in Southeast Asia. Due to its richness in nutrients, E. sinensis is usually used in traditional Oriental medicine as a basic component of anticoagulant and immune-enhancing remedies. Isolation from ethanol extract of E. sinensis yielded seven compounds, two isocoumarins (1 and 2) and four phenolic compounds 3-6. Their chemical structures were elucidated as (R)-6,8-dihydroxy-3,7-dimethyl-3,4-dihydroisochromen-1-one (monaschromone) (1), (R)-3-ethyl-6,8-dihydroxy-7-methyl-3,4-dihydroisochromen-1-one (2), 3-methoxytyramine (3), hydroxyphenyl acetic acid (4), dihydroferulic acid (5), and protocatechuic acid (6), by spectroscopic analysis. Among them, compounds 3-6 were first found in E. sinensis. Additionally, the two isocoumarins, 1 and 2, exhibited biological activity such as enhancing antioxidant response element and preventing dexamethasone-induced skeletal muscle atrophy in C2C12 myotubes.