Camosic acid structure

Masuda, T. Inaba, Y. Takeda, Y. Antioxidant mechanism of camosic acid structural identification of two oxidation products. J. Agric. Food Chem. 2001, 49, 5560-5565. 

Masuda, T., Inaba, Y. and Takeda, Y. Antioxidant mechanism of camosic acid Structural identification of two oxidation products. /. Agric. Food Chem. 49, 5560-5565 (2001). Masuda, T., Inaba, Y., Maekawa, T., Takeda, Y., Tamura, H. and Yamaguchi, H. Recovery mechanism of the antioxidant activity from camosic acid quinone, an oxidized sage and rosemary antioxidants. J. Agric. Food Chem. 50, 5863-5869 (2002). 

Hopia, A.I., Huang, S.-W., Schwarz, K., German, J.B. and Frankel, E.N. 1996. Effect of different lipid systems on antioxidant activity of rosemary constituents camosol and camosic acid with and without alpha-xocopherol. J. Agric. Food Chem. 44 2030-2036. Houlihan, C.M., Ho, C.-T. and Chang, S.S. 1984 Elucidation of the chemical structure of a novel antioxidant, rosmaridiphenol, isolated from rosemary. J. Am. Oil Chem. Soc. 61 1036-1039. 

Figure 9.12. Structures of rosemary antioxidants camosic acid, camosol, and rosmarinic acid.

Figure 12.4. Structures of quinone radicals suggested by electron spin resonance studies of camosic acid heated with oxidized methyl oleate. From Loliger et al (1996). See also Figure 9.13.

Extract of rosemary is currently approved in the EU as a natural antioxidant (E392). Camosic acid has a typical o-diphenol structure and is easily oxidised. The antioxidation mechanism is based on a coupling reaction with the peroxyl radical at the 12- or 14-position of camosic acid and subsequent transformation reactions of intermediates to an o-quinone and a hydroxy p-quinone (Figure 10.13). 

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