Studies on Biological Activity of Wood Extractives (XVII) - Components and Antioxidant activity of Alnus firma -

This study is to isolate bio-active compounds from Alnus firma and evaluate their antioxidant activity. Dried wood powder of A. firma was extracted by organic solvents and fractionated in the sequential extraction steps. The isolated compounds were characterized by EI-MS, $^{13}C-$ and $^1H-NMR$ including COSY, DEFT, HMQC, and HMBC. Antioxidant activities of the isolated compounds were evaluated by DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging effect. From the wood of A. firma, three kinds of diarylheptanoids, alnusodiol (1), alnusonol (2) and alnusone (3), and gallic acid (4) were isolated. Among these four compounds, compound 1, 2, and 3 are isolated from A. firma for the first time. The antioxidant activity of gallic acid was 93.5% at the concentration of 100 ppm. This compound showed stronger antioxidant activity than those of other isolated compounds and the reference BHT (butylated hydroxytoluene).