Carnosic Acid and Carnosol, Two Major Antioxidants of Rosemary, Act through Different Mechanisms

Abstract

Carnosic acid, a phenolic diterpene specific to the Lamiaceae family, is highly abundant in rosemary (Rosmarinus officinalis). Despite numerous industrial and medicinal/pharmaceutical applications of its antioxidative features, this compound in planta and its antioxidant mechanism have received little attention, except a few studies of rosemary plants under natural conditions. In vitro analyses, using high-performance liquid chromatography-ultraviolet and luminescence imaging, revealed that carnosic acid and its major oxidized derivative, carnosol, protect lipids from oxidation. Both compounds preserved linolenic acid and monogalactosyldiacylglycerol from singlet oxygen and from hydroxyl radical. When applied exogenously, they were both able to protect thylakoid membranes prepared from Arabidopsis (Arabidopsis thaliana) leaves against lipid peroxidation. Different levels of carnosic acid and carnosol in two contrasting rosemary varieties correlated with tolerance to lipid peroxidation. Upon reactive oxygen species (ROS) oxidation of lipids, carnosic acid was consumed and oxidized into various derivatives, including into carnosol, while carnosol resisted, suggesting that carnosic acid is a chemical quencher of ROS. The antioxidative function of carnosol relies on another mechanism, occurring directly in the lipid oxidation process. Under oxidative conditions that did not involve ROS generation, carnosol inhibited lipid peroxidation, contrary to carnosic acid. Using spin probes and electron paramagnetic resonance detection, we confirmed that carnosic acid, rather than carnosol, is a ROS quencher. Various oxidized derivatives of carnosic acid were detected in rosemary leaves in low light, indicating chronic oxidation of this compound, and accumulated in plants exposed to stress conditions, in parallel with a loss of carnosic acid, confirming that chemical quenching of ROS by carnosic acid takes place in planta.

Evaluation of the impact of chlorophyll removal techniques on polyphenols in rosemary and thyme by‐products

“…Among the quantified compounds (Tables and ), carnosic acid was the second most abundant phenolic compound in rosemary and the crude LE extracts contained significantly higher concentrations (535.5 ± 77.3 mg/100 g DW) in comparison to the MI (298.3 ± 40.5 mg/100 g DW). Previous studies have also shown that the rosemary leaves have high content of carnosic acid (Birtić, Dussort, Pierre, Bily, & Roller, ; Loussouarn et al, ). Decolorization with activated charcoal did not significantly affect the concentration of the compound in LE crude extracts, but it led to a significant reduction in the case of MI.…”

“…Carnosic acid is present exclusively in some species of the Lamiaceae family, such as rosemary, while other spices such as thyme tend to accumulate carnosol rather than carnosic acid (Loussouarn et al, ). Among the quantified compounds (Tables and ), carnosic acid was the second most abundant phenolic compound in rosemary and the crude LE extracts contained significantly higher concentrations (535.5 ± 77.3 mg/100 g DW) in comparison to the MI (298.3 ± 40.5 mg/100 g DW).…”

Rosemary powder filtrate improves the oxidative stability and antioxidant properties of rapeseed oil: potential applications for domestic cooking

“…Carnosic acid and carnosol contain a single aromatic ring with two −OH groups that can serve as H* donors and can also chelate pro‐oxidative metals, thus preventing oxidation via two mechanisms (Brewer, ). Furthermore, carnosic acid is a reactive oxygen species quencher (Loussouarn et al ., ). However, a synergistic effect from the antioxidant compounds present in rosemary is more likely since rosemary extracts demonstrate higher antioxidant activity than do the individual phenolic compounds separately (Brewer, ).…”

“…Phenolic diterpenes (carnosol, carnosic acid) are the main antioxidant compounds found in rosemary plant. These compounds exert their antioxidant activity through different mechanisms (Loussouarn et al ., ). The findings of the present study suggest that compounds present in rosemary can prevent lipid oxidation of vegetable oils by acting as secondary antioxidants and stabilising indigenous antioxidants such as tocopherols and carotenoids.…”

Refined exposure assessment of extracts of rosemary (E 392) from its use as food additive

“…Levels of carnosic acid and carnosol were available for dried rosemary leaves (112 mg/kg (Loussouarn et al, 2017)), fresh rosemary leaves (12.18 mg/kg (Luis and Johnson, 2005)) and dried sage (5.3 mg/kg (FooDB version 1.0 database 21 )). Levels of carnosic acid and carnosol were available for dried rosemary leaves (112 mg/kg (Loussouarn et al, 2017)), fresh rosemary leaves (12.18 mg/kg (Luis and Johnson, 2005)) and dried sage (5.3 mg/kg (FooDB version 1.0 database 21 )).…”