Effect of Cortex Periplocae lupane acetate on immunoregulation of human peripheral blood lymphocytes Determination of 4-methoxysalicylaldehyde in Cortex Periplocae from various habitats and at different collecting times Inductive effect of Cortex Periplocae extract on apoptosis of human gastric cancer cells BGC-823 Re—assessment of main habitats of Cortex Periplocae and original plant Periploca sepium