Novel 2-arylbenzofuran dimers and polyisoprenylated flavanones from Sophora tonkinensis

Two novel 2-arylbenzofuran dimers, shandougenines A (1) and B (2), and two new polyisoprenylated flavanones 3 (shandougenine C) and 4 (shandougenine D) were isolated from the 95% EtOH extract of Sophora tonkinensis, together with 18 known compounds. Their structures were determined on the basis of spectral data interpretation and by comparing the spectral data with that reported previously for known compounds. Shandougenine A (1) is a unique dimeric 2-arylbenzofuran with a C-3C-5‴ bond linkage. Shandougenine B (2) is the first naturally occurring dimeric 2-arylbenzofuran with a novel C-3C-3″ bond linkage. Compound 1 showed moderate DPPH free radical scavenging capacity, whereas 2 has stronger DPPH free radical and ABTS cation radical scavenging capacity than Vc. Compounds 12, 19, and 20 showed parallel DPPH free radical scavenging capacity with Vc. Compounds 1, 3, 4, 19, 20, and 22 have parallel ABTS cation radical scavenging capacity to Vc. Compounds 1, 3, 4, and 18 showed slightly stronger superoxide anion radical scavenging capacity than the known flavanone luteolin. The antioxidant activities of shandougenines A (1) and B (2) indicated that compounds 1 and 2 may represent novel scaffolds for the development of new antioxidants.