Cassia

Cassia is an evergreen tree 10–20 m tall with a straight trunk; young bark is greyish-green and matures to thick, brittle reddish-brown. Leaves are alternate to subopposite, oval to lanceolate, 8–16 cm long, glossy above and slightly glaucous beneath; small greenish-yellow flowers cluster in leaf axils and the fruit is an ovoid berry with a single seed. Stripped, dried and thinly sliced bark is the usual commodity; cassia quills are rolled from one thick bark layer rather than the many thin layers of Ceylon cinnamon.

Per Kew POWO (WCVP), Cinnamomum cassia (accepted name C. aromaticum Nees) is native to southern China — Guangdong, Guangxi, Fujian, Guizhou, Yunnan — and Vietnam (Lang Son, Cao Bang). From there it is cultivated and introduced across Southeast Asia, South Asia, Taiwan, Hainan and the Caribbean. Yunnan and Guangxi are the main producing areas, while Vietnam is known for Tra My and Lang Son cassia.

Bark oil contains 70–90% trans-cinnamaldehyde — the signature sweet-spicy compound — together with β-caryophyllene, linalool, eugenol, ethyl cinnamate and benzaldehyde. Beyond the oil, the bark also holds coumarin (cinnamomin, cassin), polysaccharides and minor flavonoids; more than 160 phytochemicals have been isolated from the species (Zhang et al., Molecules, 2019). Coumarin levels in cassia bark are markedly higher than in Ceylon cinnamon (C. verum), a key safety distinction between the two.

Cinnamaldehyde shows antibacterial, antifungal and antioxidant activity in numerous studies, and bark extract improved glycaemic control in type 2 diabetic patients in a meta-analysis by Allen et al. (Annals of Family Medicine, 2013). Cassia essential oil inhibited the enzyme tyrosinase — a skin-brightening research direction — per Chang et al. (Botanical Studies, 2013). Culinarily, cassia flavours braises, baked goods, coffee and five-spice; industrially its oil is a food flavouring, perfumery, soap and natural preservative, while the bark is the traditional Chinese medicine 'rougui'.

Because of its coumarin content, the European food safety body (EFSA, 2004) set a tolerable daily intake (TDI) of 0.1 mg/kg body weight; cassia at ordinary culinary doses is safe, but prolonged high-dose supplements should be avoided, especially with anticoagulants, in young children and in pregnancy. Cinnamomum cassia is Not Evaluated (NE) by the IUCN: most traded bark comes from plantations and home gardens with steadily growing output; in Vietnam, cassia is a key forest crop that helps replace natural-timber extraction in the northern highlands.