Anti-inflammatory activity of cinnamon (C. zeylanicum and C. cassia) extracts – identification of E-cinnamaldehyde and o-methoxy cinnamaldehyde as the most potent bioactive compounds

Abstract

Chronic inflammation is a contributing factor in many age-related diseases. In a previous study, we have shown that Sri Lankan cinnamon (C. zeylanicum) was one of the most potent anti-inflammatory foods out of 115 foods tested. However, knowledge about the exact nature of the anti-inflammatory compounds and their distribution in the two major cinnamon species used for human consumption is limited. The aim of this investigation was to determine the anti-inflammatory activity of C. zeylanicum and C. cassia and elucidate their main phytochemical compounds. When extracts were tested in LPS and IFN-γ activated RAW 264.7 macrophages, most of the anti-inflammatory activity, measured by down-regulation of nitric oxide and TNF-α production, was observed in the organic extracts. The most abundant compounds in these extracts were E-cinnamaldehyde and o-methoxycinnamaldehyde. The highest concentration of E-cinnamaldehyde was found in the DCM extract of C. zeylanicum or C. cassia (31 and 34 mg g⁻¹ of cinnamon, respectively). When these and other constituents were tested for their anti-inflammatory activity in RAW 264.7 and J774A.1 macrophages, the most potent compounds were E-cinnamaldehyde and o-methoxycinnamaldehyde, which exhibited IC₅₀ values for NO with RAW 264.7 cells of 55 ± 9 μM (7.3 ± 1.2 μg mL⁻¹) and 35 ± 9 μM (5.7 ± 1.5 μg mL⁻¹), respectively; and IC₅₀ values for TNF-α of 63 ± 9 μM (8.3 ± 1.2 μg mL⁻¹) and 78 ± 16 μM (12.6 ± 2.6 μg mL⁻¹), respectively. If therapeutic concentrations can be achieved in target tissues, cinnamon and its components may be useful in the treatment of age-related inflammatory conditions.