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 calycinum. The absolute configurations of compounds 1–4 were assigned using Marfey’s method. The structure of compound 5 was revised from cyclo(Pro1–Phe2–Leu3–Ala4–Thr5–Pro6–Ala7–Gly8) to cyclo(Pro1–Pro2–Ala3–Gly4–Leu5–Ala6–Thr7–Phe8) 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 (O2•–) production, and cell viability in mesangial cells, and on nitric oxide (NO) production in macrophage cells.

从 Brachystemma calycinum 的地上部分中分离得到四种新的环状肽，即 brachystemins F–I (1–4)，以及十一条已知化合物。通过 Marfey 方法确定了化合物 1–4 的绝对构型。利用 QTOF/MS 和 X射线衍射分析，将化合物 5 的结构从 cyclo(Pro1–Phe2–Leu3–Ala4–Thr5–Pro6–Ala7–Gly8) 修订为 cyclo(Pro1–Pro2–Ala3–Gly4–Leu5–Ala6–Thr7–Phe8)。针对含氮化合物，评估了其在抑制单核细胞趋化因子配体 2 (CCL-2)、白细胞介素 6 (IL-6) 和 IV 型胶原分泌于高糖刺激的肾小球细胞中的抑制作用。化合物 5 的作用被评估于肾小球细胞中胶原蛋白 I、活性氧 (ROS)、超氧阴离子 (O2•–) 的产生以及细胞活力，以及在巨噬细胞中一氧化氮 (NO) 的产生。