Studies on Physiologically Active Substances in Citrus Fruit Peel. Part XXI. Structures of New Cyclic Peptides in Young Unshiu (Citrus unshiu MARCOV.), Orange (Citrus sinensis OSBECK.) and Amanatsu (Citrus natsudaidai) Peelings.

Four cyclic peptides were isolated from young unshiu (unripe fruit), orange and amanatsu peelings, and their structures were established on the basis of FAB-MS (CID method) and 2D-NMR spectroscopic data, and by chemical evidence. They were each found to consist of seven or eight amino acids. In the present study, compounds 1-4 are shown to be new cyclic Peptides.