Cynasibirolide A, One New Humulanolide Sesquiterpene from Cynanchum acutum subsp. sibiricum.

Cynasibirolide A (1), one new humulanolide sesquiterpene, together with four known analogs, asteriscanolide (2), (1S,8S)-8-hydroxyhumula-2Z,6E,9E-trien-1,12-olide (3), (1S,7R)-8-oxohumula-2Z,9E-dien-1,12-olide (4), and (+)-6,7,9,10-tetrahydroasteriscunolide (5) were isolated from the roots and rhizomes of Cynanchum acutum subsp. sibiricum. Their structures and configurations were elucidated by spectroscopic methods, including 2D-NMR techniques, and the structure of 1 was confirmed by single-crystal X-ray diffraction. All compounds were evaluated for their anti-complementary activity in vitro, and compound 3 exhibited anti-complement effect with CH50 value of 0.45 mM.

Oplopane Sesquiterpenes from Ligularia knorringiana and Their Anti-Complementary Activity.

Three new oplopane sesquiterpenes, knorringianalarins D - F (1 - 3, respectively), and five known analogues (4 - 8, respectively), were isolated from the roots and rhizomes of Ligularia knorringiana. The structures of three new compounds were identified as 4-acetoxy-11α,12-epoxy-2ß-hydroxy-3ß-(2-methylbutyryloxy)-9α-(4-methylsenecioyloxy)oplop-10(14)-ene (1), 3ß,4-diacetoxy-9α-(4-acetoxy-4-methylsenecioyloxy)-11α,12-epoxy-8α-(2-methylbutyryloxy)oplop-10(14)-ene (2), and (1R,5R,6R,7R,9R)-5,9,11-trihydroxy-4,15-dinoroplop-10(14)-en-3-one (3) based on spectroscopic methods including 1D- and 2D-NMR, mass spectrometry, and CD spectroscopy techniques. All compounds were evaluated for their anti-complementary activity on the classical pathway of the complement system in vitro. Among which, three oplopane sesquiterpenes (3, 7, and 8) exhibited better anti-complementary effects with CH50 values ranging from 0.33 to 0.89 mm, which are plausible candidates for developing potent anti-complementary agents.