Aporphine and phenanthrene alkaloids with antioxidant activity from the roots of Stephania tetrandra.

Five new alkaloids (1–5), including three new aporphine alkaloids and two new phenanthrene alkaloids, together with 10 known compounds (6–15) were obtained from the roots of Stephania tetrandra. Their structures were elucidated by spectroscopic methods, single-crystal X-ray diffraction, and electronic circular dichroism analyses. Compounds 7–10, and 13 showed antioxidant activities with malondialdehyde (MDA) inhibitory rates of 62.50 ± 1.91 to 98.44 ± 0.34% at the concentration of 10 μM.