Caffeic acid is an organic compound. The structure of caffeic acid (aromatic core, conjugated double bond, and hydroxyl groups) allows it to function as an antioxidant.
Caffeic acid (50 mg/kg) reduces blood glucose levels in streptozocin-induced diabetic mice.
In depressed rats, caffeic acid (10 and 30 mg/kg) normalized noradrenalin and tryptophan levels in a dose-dependent manner.
BDNF, a neurotrophin that modulates neuroplasticity in the brain, is regularly decreased in depressed patients.Caffeic acid also increased the expression of brain-derived neurotrophic factor (BDNF) in stressed mice; the effect was mediated by 5-lipoxygenase inhibition [106].
The main components of plaques found in the brains of patients with Alzheimer’s disease consist of β-amyloid peptides and tau proteins.
The essential step for tau protein aggregation is tau phosphorylation which may also play a role in initiating β-amyloid toxicity. One of the kinases that phosphorylate tau protein is glycogen synthase kinase-3 beta (GSK3β); insulin signaling inhibits the activity of this kinase. Therefore, a hypothesis suggests that GSK3β deregulation in neurons may be a key point in developing Alzheimer’s disease.
In the brain of hyperinsulinemic rats, caffeic acid normalized superoxide dismutase (SOD) activity and glutathione levels, inhibited glycogen synthase kinase 3β (GSK3β) activity, and decreased the level of β-amyloid and phosphorylated tau protein.
Feeding hyperinsulinemic rats with caffeic acid (30 mg/kg b.w./day) for 30 weeks significantly improved their memory and learning impairments caused by a high-fat diet.
The concurrent effects of caffeic acid on atherosclerotic lesions and cognitive decline were explored in a new article by using the ApoE (Alzheimer) mice model.
A two months' administration of 20 mg/kg caffeic acid or saline was given once two days intraperitoneally to 5-month-old female ApoE mice.
The scientists found that the caffeic acid treatment reduced the atherosclerotic lesions in the whole aorta and aortic sinus of the resulting 7-month-old ApoE mice by roughly 50%, compared with the saline control.
Meanwhile, the cognitive decline of treated mice were significantly alleviated, as measured by Y-maze and Morris water maze tasks. A reduced accumulation of β-amyloid in the hippocampus was also observed. These effects were associated with elevated serum HDL-c concentration, upregulated ABCA1 and ABCG1 mRNA levels, as well as decrease local inflammation and reduced levels of serum pro-inflammatory cytokines including TNF-α, IL-6 and MCP-1.
These obtained results suggested the preventive and therapeutic potential of caffeic acid against atherosclerosis and Alzheimer's disease during aging.
Free caffeic acid can be found in a variety of herbs of the mint family, especially thyme, sage and spearmint (at about 20 mg per 100 g), and in spices, such as Ceylon cinnamon and star anise (at about 22 mg per 100 g).