Cyclopeptide Alkaloids from Ziziphus apetala.

Six novel Ia₃-type cyclopeptide alkaloids (1-6) were isolated from stems of Ziziphus apetala. Compound 5 and the known compounds mauritine A (7) and mauritine F (8) were isolated from the roots. Their structures were determined by spectroscopic analyses and chemical methods. The total alkaloids from the roots and the isolated cyclopeptide alkaloids were tested for antidepressant behavior on mice, cytotoxicity, and 11β-hydroxysteroid dehydrogenase (11β-HSD) inhibition in vitro. Only mauritine A (7) showed inhibitory activity on 11β-HSD1, with IC₅₀ values of 52.0 (human) and 31.2 μg/mL (mouse).