Variations in essential oil yields and compositions of Cinnamomum cassia leaves at different developmental stages

• Oil cell ontogeny and its relationship with the oil yields and compositions were first revealed.
• The developmental degree of oil cells was related to the oil yields and quality.
• The leaves of the 2-year-old branch had the highest quality.

To investigate the effect of the developmental stages of the cassia leaf on the yields and composition of its essential oils, volatile compounds of cassia leaves at different developmental stages were detected by GC–MS and FT-IR analysis. The relationships between the oil cell ontogeny and oil accumulation with essential oil yields and compositions were systematically analyzed. The results indicated that the leaves of the 2-year-old branch had the highest density of oil cells (6.91 n/mm2) and the maximum percentage of oil cells at the oil saturation stage (48.05%), which coincided with the highest oil yield (2.12%) and trans-cinnamaldehyde content (66.47%). The oils were less accumulated in the 1–4 leaves of annual branch and were mostly disintegrated in the leaves of 4 years old branch, therefore the lower percentages of oil cells at oil saturation stage (6.72 and 33.71%, respectively) resulted in the lower oil yields (1.01 and 0.54%, respectively) and lower percentages of trans-cinnamaldehyde (57.89% and 61.57%, respectively). Curve fitting of the FT-IR results agreed with that of the GC–MS analysis. These results can provide reference information for the rational utilization of cinnamon resources and harvest of cassia leaves.