27-Norcholestane, is a chemical compound with the formula C 26H 46, that is a steroid derivative. 27-Norcholestane is used as a biomarker to constrain the source age of sediments and petroleum through the ratio between 24-norcholestane and 27-norcholestane (norcholestane ratio, NCR), especially when used with other age diagnostic biomarkers, like oleanane.[1]
^Holba, A. G.; Dzou, L. I. P.; Masterson, W. D.; Hughes, W. B.; Huizinga, B. J.; Singletary, M. S.; Moldowan, J. M.; Mello, M. R.; Tegelaar, E. (1998-11-01). "Application of 24-norcholestanes for constraining source age of petroleum". Organic Geochemistry. 29 (5): 1269–1283. Bibcode:1998OrGeo..29.1269H. doi:10.1016/S0146-6380(98)00184-3. ISSN0146-6380.