Paralemnanoids A–K, new norsesquiterpenoids and sesquiterpenoids with hepatoprotective activity from the soft coral Paralemnalia sp.

Abstract

Eleven nardosinane-type compounds, including a norsesquiterpenoid featuring a novel carbon skeleton designated as paralemnanoid A (1), and ten additional norsesquiterpenoids identified as paralemnanoids B − K (2 − 11), were isolated from the South China Sea soft coral Paralemnalia sp.. Comprehensive structural elucidation of compounds 1 − 11 was achieved through an integrated analytical approach, combining including NMR spectroscopy, HRESIMS, single-crystal X-ray diffraction analysis, DP4 + probability assessments, ECD calculations, and literature comparisons. Furthermore, we proposed that the novel poly-isoprenoid scaffold paralemnanoid A (1) originates from paralemnanoid B (2) through sequential oxidative modifications followed by non-enzymatic skeletal rearrangements. The hepatoprotective effects of compounds 1 − 11 were assessed through bioassays, revealing that paralemnanoids A (1) and E (5) exhibited moderate hepatoprotective activity at a concentration of 20 μmol/L in the zebrafish model. This study expands the chemical diversity of marine-derived nardosinane-type terpenoids and provides new insights into their potential therapeutic applications.

Keywords

Soft coral / Paralemnalia sp. / Nardosinanes / Configuration determination / Hepatoprotective activity / X-ray diffraction

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