Bioactive Compounds from the Aerial Parts of Brachystemma calycinum and Structural Revision of an Octacyclopeptide

Four new cyclic peptides, brachystemins F-I (1-4), and 11 known compounds were isolated from the aerial parts of Brachystemma calycinim. The absolute configurations of compounds 1-4 were assigned using Marfey's method. The structure of compound 5 was revised from cyclo-(Pro(1)-Phe(2)-Leu(3)-Ala(4)-Thr(5)-Pro(6)-Ala(7)-Gly(8)) to cyclo-(Pro(1)-Pro(2)-Ala(3)-Gly(4)-Leu(5)-Ala(6)-Thr(7)-Phe(8)) with QTOF/MS and X-ray diffraction analysis. The N-containing compounds were assessed for their inhibitory effects on the secretion of monocyte chemokine ligand 2 (CCL-2), interleukin 6 (IL-6), and collagen IV against high-glucose-stimulated mesangial cells. Compound 5 was evaluated for its effects on collagen I, reactive oxygen species (ROS), superoxide anion (O(2)(center dot-)) production, and cell viability in mesangial cells, and on nitric oxide (NO) production in macrophage cells.