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Antioxidant activity of lipid‐soluble phenolic diterpenes from rosemary
Author(s) -
Richheimer Steven L.,
Bernart Matthew W.,
King Greg A.,
Kent Michael C.,
Beiley David T.
Publication year - 1996
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02523927
Subject(s) - carnosic acid , rosmarinus , butylated hydroxytoluene , butylated hydroxyanisole , chemistry , officinalis , diterpene , antioxidant , organic chemistry , phenols , food science , essential oil , botany , biology
A high‐performance liquid chromatography method for analyzing the phenolic diterpenes present in rosemary ( Rosmarinus officinalis L.) and commercial rosemary extracts is reported. Carnosic acid was the major phenolic diterpene present in rosemary leaves, with lesser amounts of 12‐methoxycarnosic acid and carnosol. Several commercial rosemary extracts also were analyzed by this method, and in addition to these three compounds other phenolic diterpenes, such as 7‐methoxyrosmanol, 7‐methoxy‐epirosmanol, and rosmanol, were found in some samples. These latter three compounds seem to be artifacts, produced from carnosic acid by oxidation and cyclization. The major phenolic diterpenes were isolated, and their relative antioxidatn activities in soybean oil were measured by the Rancimat. The potency of carnosic acid was more than twice that of any other compound. The antioxidant activity of pure carnosic acid was compared to butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tertiary butylhydroquinone (TBHQ) and was several times greater than BHT and BHA but less than TBHQ. Nuclear magnetic resonance data for several of the compounds that were incompletely characterized in previous literature are reported.