Phenolic diterpenes, particularly those found in plants such as rosemary (Rosmarinus officinalis) and sage (Salvia officinalis), have been studied for their antioxidant activities, which are directly related to neutralizing free radical damage. Key phenolic diterpenes like carnosic acid, carnosol, and rosmanol have demonstrated significant free radical scavenging and chain-breaking antioxidant properties in both in vitro and in vivo studies.

Several peer-reviewed studies have shown that these compounds can protect cellular components from oxidative stress by donating electrons to neutralize reactive oxygen species (ROS). For example, carnosic acid has been reported to protect neuronal and hepatic cells from oxidative injury, and to increase the activities of endogenous antioxidant enzymes. Additionally, rosemary extract rich in phenolic diterpenes has been shown to reduce lipid peroxidation and DNA damage in animal models.

The antioxidant mechanisms of phenolic diterpenes are well characterized, and they are widely used in the food industry as natural preservatives to prevent oxidation. While most evidence is preclinical, there is a strong biochemical rationale and consistent experimental data supporting their role in mitigating free radical-induced cellular damage. However, large-scale clinical trials in humans specifically targeting disease outcomes related to free radical damage remain limited.