Cinnamon from the dried inner bark of Cinnamomum is the most important and popular spice in the world. There are mainly two sources of cinnamon, Ceylon from Sri Lanka, South India and Cassia from China. These two kinds of cinnamon make no distinction and both of them are of similar components, flavor and effects, only differ in the proportion of constituents.
The major component of cinnamon is the essential oil made up of cinnamaldehyde, the factor responsible for its aroma and flavor. The content of cinnamaldehyde can be up to 90% depending on the species. Besides, there are cinnamic acid and cinnamic alcohol acetate. Rich eugenol is also found in the leaves of Cinnamomum. Among them, cinnamaldehyde is believed to be the most effective factor against various diseases. It is reported to have strong antioxidant, anti-inflammatory, anti-diabetic anti-microbial properties that can be applied in daily health care and pharmaceutical.
Antioxidant compounds in cinnamon have obvious inhibitory effects on free radical damage and metabolic disease syndrome caused by aging problems. Its ethyl ether, water and methanol extracts are also proved to have strong antioxidant activity and can significantly inhibit the oxidation of fatty acid and lipid peroxidation in vitro. The active ingredient responsible for that is E-cinnamaldehyde which is rich in cinnamon leaves.
The anti-inflammatory activity of cinnamon was first reported in 1987. So far, a variety of cinnamon extracts from different sites have been found to have significant anti-inflammatory properties through their mechanisms are different. For example, the mechanism of hydroxycinnamaldehyde is to reduce the production of nitric oxide by inhibiting the activation of nuclear factor of NF-κB. Studies show that various cinnamon extracts exert their anti-inflammatory activity by inhibiting the synthesis of induced nitric oxide and COX 2 in central nervous system.
The anti-tumor activity of cinnamon is shown to inhibit several human cancer cell lines including breast, leukemia, ovarian and lung tumor cells. In addition, cinnamaldehyde has obvious killing, inhibiting or cytotoxic effects on various tumor cells in vitro and in vivo. Study demonstrates that in vitro treatment of colon cancer HCT cells with the minimum concentration of cinnamaldehyde (0.5-2.5 mmol/L) for 4-6 hours can significantly induce DNA damage, inhibit DNA repair and recombination, and reduce the occurrence of spontaneous mutations.
More importantly, with these properties, many trials have explored the beneficial effects of cinnamon in diabetes, arthritis and Alzheimer’s disease in recent years.
Type 2 Diabetes Mellitus
Type 2 diabetes mellitus is called adult-onset diabetes. The insulin-producing ability of these patients is not completely lost, and some patients even produce too much insulin, but the effect of insulin fails to function in a normal level. Cinnamon has insulin-mimetic properties because its biologically active substances can effectively enhance glucose uptake by activating insulin receptor kinase activity, autophosphorylation of the insulin receptor, and glycogen synthase activity. A study shows that it is methyl hydroxyl chalcone polymer from cinnamon that makes fat cells more responsive to insulin, thus enhances its effect.
Nearly all of the research on human and animals indicate that consumption of cinnamon can lower blood sugar and prevent diabetes, even cardiovascular diseases. A research carried out by Alam Khan et al. demonstrates that intake of 1, 3, or 6 g of cinnamon per day reduces serum glucose, triglyceride, LDL cholesterol, and total cholesterol in people with type 2 diabetes and suggest that the inclusion of cinnamon in the diet of people with type 2 diabetes will reduce risk factors associated with diabetes and cardiovascular diseases. According to a health association in England, only 2 g of cinnamon a day can significantly reduce the risk of developing diabetes.
Using cinnamon as an herbal remedy in treating rheumatoid arthritis has a long tradition in Chinese medicine. However, the molecular mechanism remains unclear. The study carried out by Panwang Liu et al. has made an effort in revealing the mechanism of this herb. It concludes that cinnamaldehyde in cinnamon significantly reduces the synovial inflammation, possibly due to suppression of the expressions of pro-inflammatory cytokines, especially the IL-1β. Further investigation found that CA also suppresses the activity of HIF-1α by inhibiting the accumulation of succinate in the cytoplasm.
Alzheimer’s disease is a progressive, neurodegenerative, and irreversible brain disorder with symptoms such as memory loss, confusion, impaired judgments, and loss of language skills. There are a number of studies that identify the accumulation of soluble oligomeric assemblies of β-amyloid polypeptide as the main cause of the development of Alzheimer’s disease. Some recent studies come up with the conclusion that cinnamon can inhibit the formation of toxic β-amyloid polypeptide oligomers and prevents the toxicity of β-amyloid polypeptide on neuronal cells. Studies also found the oral administration of cinnamon extract leads to a marked decrease in 56 kDa β-amyloid polypeptide oligomers, reduction of plaques and improvement in cognitive behavior. Since most drugs against Alzheimer’s disease are developed based on this mechanism, cinnamon could also play a role in the fight against this disease.
As a long-used spice and medicine, cinnamon has become indispensible in daily life. With the continuous unraveling of the mechanism of cinnamon in traditional Chinese medicine, the role of cinnamon has become more scientifically explained and will be applied in the treatment and prevention of more diseases.
 Frydman-Marom A, Levin A, Farfara D, et al. orally administrated cinnamon extract reduces b-Amyloid oligomerization and corrects cognitive impairment in Alzheimer’s disease animal models. PLoS One. 2011;28:e16564.
 Liu P, Wang J, Wen W, et al. Cinnamaldehyde suppresses NLRP3 derived IL-1β via activating succinate/HIF-1 in rheumatoid arthritis rats. Int Immunopharmacol. 2020;84:106570. doi:10.1016/j.intimp.2020.106570
 Rafie Hamidpour, Mohsen Hamidpour, Soheila Hamidpour, et al. Cinnamon from the selection of traditional applications to its novel effects on the inhibition of angiogenesis in cancer cells and prevention of Alzheimer’s disease, and a series of functions such as antioxidant, anticholesterol, antidiabetes, antibacterial, antifungal, nematicidal, acaracidal, and repellent activities. Journal of Traditional and Complementary Medicine, 2015, 5(2):66-70.
 Khan A, Safdar M, Ali Khan MM, Khattak KN, Anderson RA. Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care. 2003;26(12):3215-3218. doi:10.2337/diacare.26.12.3215