Extraction time and temperature affect the extraction efficiencies of coumarin and phenylpropanoids from Cinnamomum cassia bark using a microwave-assisted extraction method

Microwave-assisted extraction (MAE), an efficient extraction tool, was employed to extract a coumarin and five phenylpropanoids (cinnamic acid, cinnamyl alcohol, cinnamaldehyde, 2-hydroxycinnamadehyde, and 2-methoxycinnamaldehyde) from Cinnamomum cassia bark using water as the extraction solvent. Six marker compounds were quantified by high-performance liquid chromatography-diode array detector using a validated analytical method. To investigate the influences of temperature and time on the extraction yields of the six marker compounds, the water extracts of C. cassia bark were prepared using a MAE method at six different extraction temperatures (70, 75, 80, 85, 90, and 95 °C) and times (2, 4, 6, 8, 10, and 12 min). Their influences were assessed by multiple regression analysis. The results obtained demonstrated that higher extraction temperature and longer extraction time positively affected coumarin and cinnamyl alcohol contents, but negatively affected extract contents of cinnamic acid, cinnamaldehyde and 2-hydroxycinnamaldehyde (all p-< 0.05). The extraction of 2-methoxycinnamaldehyde was affected by both positively and negatively by increasing temperature and time. These changes during MAE were assumed by the chemical natures of the marker compounds with various functional groups. In conclusion, temperature and times significantly affected the extraction efficiencies of a coumarin and five phenylpropanoids from C. cassia bark when a water-based MAE method was used. This study provides a novel approach to the preparation of the water extract of C. cassia bark using MAE.