Abstract
Hipposponlachnins A (1) and B (2), possessing an unprecedented tetracyclo [9.3.0.02,8.03,7] tetradecane ring system, and the probable biogenetic precursor [3, (1R*,2E,4R*,7E,10S*,11S*,12R*)-10, 18-diacetoxydolabella-2,7-dien-6-one] of 1‒2 were isolated from the South China Sea marine sponge Hippospongia lachne. The structures of the novel compounds were determined using integrated spectroscopic methods in combination with single-crystal X-ray diffraction analysis. Compounds 1‒2 showed potent inhibitory activity on the release of β-hexosaminidase, a biomarker for degranulation, as well as the production of pro-inflammatory cytokine IL-4 and lipid mediator LTB4 in DNP-IgE-stimulated RBL-2H3 cells.
Highlights
Allergy is an abnormal adaptive immune response against allergens, such as pollen, food, dust mites, cosmetics, mold spores, and animal hairs1,2. β-Hexosaminidase, typically released in addition to histamine by mast cells after stimulation with antigen, has been used as a biomarker for antigen-induced degranulation in rat basophilic leukemia (RBL-2H3) cells[3]
Only a few natural compounds with anti-allergic activity have been isolated to date[5]
As part of our searching for anti-allergic secondary metabolites from marine sponges, we investigated the sponge Hippospongia lachne, collected from the Xisha Islands of China in March 2013
Summary
The planar structure of 1 was elucidated via a detailed analysis of 2D NMR data (Fig. 2). The overall appearance of the NMR spectrum of 2 revealed close structural similarity between 1 and 2, indicating the presence of the same tetracyclo [9.3.0.02,8.03,7]. Detailed analysis of the single-crystal X-ray diffraction patterns of 2 confirmed this hypothesis and established the absolute configuration of 2 as 1R,2R,3S,4R,7S,8S,10S,11S,12R (Fig. 3). Only one diterpenoid with a similar skeleton, namely vulgarisin A, derived from the Chinese Medicinal Plant Prunella vulgaris, has been reported to date[19] These two novel compounds represented an unprecedented tetracyclo [9.3.0.02,8.03,7] tetradecane ring system from marine source for the first time. The potent inhibitory activity on the release of β-hexosaminidase for 1‒2 suggested that these two bioactive diterpenoids can be the potential therapeutic agents for the treatment of allergy
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