Three new Diels-Alder type adducts from the stem bark of Morus cathayana

Three new Diels-Alder type adducts cathayanons C (1), D (2), and E (3), together with one known compound sanggenon C (4), were isolated from the stem bark of Morus cathayana. Their structures were fully elucidated by spectroscopic and chemical methods. Compound 2 showed good anti-oxidation activity with the inhibitory rate of malondialdehyde being 88% at a concentration of 10-6mol/l.