Relevance of the carnosic acid/carnosol ratio for the level of rosemary diterpene transfer and for improving lamb meat antioxidant status

• We evaluate the level of transfer of two typified rosemary extracts in lamb tissues.
• A higher presence of carnosol improves the deposition of diterpens in lambs.
• A new metabolite, C19H22O3, from the ruminal diterpens metabolism is described.
• The antioxidant status of lamb tissues is enhanced by carnosol deposition.
• Carnosol stabilises the diterpenic fraction during feed manufacture.

The aim of the present work was to evaluate whether the relation between the concentrations of the two major diterpenes present in two typified rosemary extracts affects their levels of deposition and antioxidant capacity in different lamb tissues. The composition of the extracts expressed as percentage of weight/weight was 1:1 (14–16)% and 2:1 (25–11)% (carnosic acid–carnosol), respectively. Thirty weaned lambs were assigned randomly to three homogeneous groups. One group was fed a basal diet as a control and the diets of the other two were enriched with rosemary extracts 1:1 and 2:1, respectively. HPLC–ESI-MS/TOF identified a metabolite (C19H22O3) described for the first time in lamb tissues, along with carnosol, carnosic acid, rosmanol and carnosol-p-quinone. The results obtained corroborate the importance of the presence of carnosol in the dietary administration of rosemary extract as a way of improving the stability of the diterpene fraction during feed manufacturing and the level of deposition and antioxidant efficacy of diterpenes after ruminal fermentation.