Abstract
A first phenalenon derivative with an acetyl side chain at C-8, 8-acetyl-9-hydroxy-3-methoxy-7-methyl-1-phenalenon (compound 1), and a pair of new sesquilignan epimers at C-7″ of hedyotol C and hedyotol D analogs, hedyotol C 7″-O-β-d-glucopyranoside (compound 2) and hedyotol D 7″-O-β-d-glucopyranoside (compound 3) were isolated from the aerial parts of Helicteres angustifolia together with nine known compounds (4–12). Their structures were elucidated on the basis of spectroscopic methods, including mass spectroscopy, and 1D and 2D nuclear magnetic resonance. Eleven isolates exhibited anti-complementary activity. In particular, compounds 4 and 5 exhibited potent anti-complementary activities against the classical and alternative pathways with CH50 values of 0.040 ± 0.009 and 0.009 ± 0.002 mM, and AP50 values of 0.105 ± 0.015 and 0.021 ± 0.003 mM, respectively. The targets of compounds 4 and 5 in the complement activation cascade were also identified. In conclusion, the anti-complementary components of H. angustifolia possessed chemical diversity and consisted mostly of flavonoids and lignans in this study.
Highlights
The complement system, as a chief component of innate immunity, plays a significant role in host immune defense against infection and in the clearance of antigen-antibody complexes from the bloodstream
In our search for anti-complementary activity compounds from plants, the 95% ethanolic extract of H. angustifolia possessed a potent anti-complementary activity
The EtOAc-soluble fraction was concentrated under reduced pressure to produce a residue that was subjected to multiple chromatographies
Summary
The complement system, as a chief component of innate immunity, plays a significant role in host immune defense against infection and in the clearance of antigen-antibody complexes from the bloodstream. It can be activated by a cascade mechanism through the classical pathway (CP), alternative pathway (AP) or the lectin pathway [1]. In our effort to search for anti-complementary agents from Chinese herb medicines and to clarify their anti-complementary constituents [3,15,16], an ethanolic extract of the aerial parts of H. angustifolia was found to show a potent anti-complementary activity, which encouraged us to investigate its anti-complementary constituents systematically. The target identification in the complement activation cascade has been investigated for anti-complementary constituents
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