Two new phenolic compounds from the leaves of Alnus sibirica Fisch. ex Turcz.

Two new phenolic compounds, 4-O-glucopyranosyl-5-O-caffeoylshikimic acid (1) and 2,3-digalloyl oregonin (2), were isolated along with eight known phenolic compounds (3-10) from an 80% acetone extract of Alnus sibirica leaves. The chemical structures of these compounds were elucidated using 1D/2D nuclear magnetic resonance and high resolution-MS. The anti-oxidative activities of these compounds were determined by assaying their 1,1-diphenyl-2-picrylhydrazyl radical and nitroblue tetrazolium superoxide anion scavenging activity. All of the isolated phenolic compounds (1-10) exhibited potent anti-oxidative activities. In particular, 2 and 4, which are diarylheptanoids, and 10 which is ellagitannin exhibited excellent anti-oxidative activities with almost the same potency as that of the positive controls L-ascorbic acid and allopurinol.