Natural antioxidants as food and beverage ingredients - Natural Food Additives, Ingredients and Flavourings - page 108

iso -rosmanol, methyl-epirosmanol, rosmanol, rosmanidiphenol, rosmarinic acid,
rosmariquinone and ursolic acid) in various food systems (Etter 2004).
The most abundant active phenolic molecules are carnosic acid and carnosol,
which are oil-soluble, and rosmarinic acid, which is water-soluble. These are very
effi cacious antioxidants in a variety of foods and beverages (Fig. 5.3). The
antioxidant mode of action is believed to be mostly due to radical scavenging.
Additionally, carnosic acid and carnosol are peroxyl radical scavengers; they are
more effective against lipid peroxidation than propyl gallate in certain in vivo
models (Aruoma et al. 1992). In addition, rosmarinic acid is a better superoxide
scavenger than ascorbic acid (Nakamura et al. 1998). Figure 5.4 depicts how
carnosic acid, which has super-stoichiometric radical scavenging capabilities, can
rearrange and form four new, sequential intermediates that can also act as
antioxidants (Masuda et al. 2001).
A recent review stated that the extract of rosemary leaves exhibited the
most effective activity among a variety of herbs tested (Nakatani 2000). To
improve further on the potency of rosemary extract, other antioxidants might
be incorporated into an antioxidant composition to seek synergistic effects.
Hence, rosemary preparations are often used with tocopherols (Pokorný et al.
2001), citric acid (Irwandi et al. 2004) or ascorbic acid to protect oils from
developing rancidity.
Antioxidant properties extend to other members of the Labiatae family and to
other spices. Sage and oregano were among the Labiatae spices that showed
potency in a widely acknowledged early study (Chipault et al. 1956).

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Fig. 5.3 Rosemary's predominant phenolics.