ANSWER

Rosemary extracts contain a large number of phenolic compounds including carnosic acid, carnosol and rosmarinic acid, which are strong natural antioxidants. The phenolic antioxidants are related primarily to their antioxidant activity resulting in increased shelf life of food products.

Differences of Carnosic acid and Rosmarinic acid

Carnosic acid is lipid and oil soluble whereas Rosmarinic acid is water soluble. Carnosic acid also has a higher content of phenolic acid compared to Rosmarinic acid. Carnosic acid is the major component in the phenolic diterpenoid fraction from R. officinalis (Firas, A.A., 2011). Degradation of rosemary extract was observed and it showed much slower rates of degradation compared to carnosic acid (Zhang et al., 2012).

Carnosic acid has an abietane structure containing an isoprene skeleton unlike other antioxidants, therefore it exhibit a considerably higher oxidation-inhibiting effect on fats and oils. In addition, carnosol and carnosic acid also has a conjugated double bond in a structure, therefore carnosol and carnosic acid tend to be structurally stabilized against radicals, even when undergoing influence of the radicals and, as a result, can exhibit a high photo-deterioration inhibiting effect (European Patent No. EP2261304 A2, 2010).

References

Firas, A. A. (2011). Antimicrobial activity of carnosic acid isolated from Rosmarinus officinalis L. Leaves. Tikrit Journal of Pure Science.16(4), 6-11.

Kido, K. (2010). Degradation Inhibitor. European Patent No. EP2261304 A2.

Zhang, Y., Smuts, J., Dodbiba, E., Rangarajan, R., Lang, J., & Armstrong, D. (2012). Degradation Study of Carnosic Acid, Carnosol, Rosmarinic Acid, and Rosemary Extract (Rosmarinus officinalis L.) Assessed Using HPLC. Journal Of Agricultural And Food Chemistry, 60(36), 9305-9314. https://doi.org/10.1021/jf302179c