Constituents of the Stem of Nauclea orientalis

A new α-pinene derivative (1) was isolated from the stem of Nauclea orientalis (L.) L. (Rubiaceae), together with twelve known compounds, including four terpenoids, loganetin (2), loganin (3), sweroside (4), grandifloroside (5), four simple phenols, methyl protocatechuate (6), trans-p-coumaric acid (7), 3-(2,4- dihydroxylphenyl)propanoic acid (8), methyl 3-(2,4-dihydroxylphenyl)propanoate (9), two coumarin glucosides, skimmin (10), adicardin (11), an anthraquinone, aloe emodin (12), and a lignan, (+)-pinoresinol (13). Their structures were elucidated on the basis of spectroscopic data. All compounds were tested for DPPH free radical scavenging and lipid peroxidation inhibitory activities. Among them, compounds 5 and 6 displayed strong antioxidant activity with IC50 values of 6.6 and 67.9 µM, 12.4 and 813.0 µM, respectively.