Ilimaquinone and 5-epi-Ilimaquinone : beyond a simple diastereomeric ratio, biosynthetic considerations from NMR-based analysis Boufridi, A. Lachkar, D. Erpenbeck, D. Beniddir, M.A. Evanno, L. /Petek, Sylvain /Debitus, Cécile Poupon, E. Dactylospongia metachromia and Dactylospongia elegans collected from French Polynesia were studied with a particular focus on the variation of the diastereomeric ratio between ilimaquinone (4) and 5-epi-ilimaquinone (5). More than 100 samples, covering an area of 4100km2, were studied to try to clarify this intriguing issue. Nuclear magnetic resonance appeared as the non-destructive, straightforward technique of choice for a relative quantitative study. A random distribution, unique at that point in nature, is observed and leads to biosynthetic considerations. Biological evaluation of both compounds was also performed and showed moderate discrepancies in cytotoxicity and apoptosis induction. 2017 text https://www.documentation.ird.fr/hor/fdi:010069903 fdi:010069903 Boufridi A., Lachkar D., Erpenbeck D., Beniddir M.A., Evanno L., Petek Sylvain, Debitus Cécile, Poupon E.. Ilimaquinone and 5-epi-Ilimaquinone : beyond a simple diastereomeric ratio, biosynthetic considerations from NMR-based analysis. 2017, 70 (6), 743-750 EN POLYNESIE FRANCAISE PACIFIQUE