The roots, bark, and leaves of Cinnamomum camphora are rich in essential oils, which mainly comprised monoterpenes and sesquiterpenes. Although the essential oils obtained from C. camphora have been widely used in pharmaceutical, medicinal, perfume, and food industries, the molecular mechanisms underlying terpenoid biosynthesis are poorly understood. To address this lack of knowledge, we performed transcriptome analysis to investigate the key regulatory genes involved in terpenoid biosynthesis in C. camphora . High-oil-yield trees of linalool type and low-oil-yield trees were used to assemble a de novo transcriptome of C. camphora . A total of 121,285 unigenes were assembled, and the total length, average length, N50, and GC content of unigenes were 87,869,987, 724, 1,063, and 41.1%, respectively. Comparison of the transcriptome profiles of linalool-type C. camphora with trees of low oil yield resulted in a total of 3,689 differentially expressed unigenes, among them 31 candidate genes had annotations associated with metabolism of terpenoids and polyketides, including four in the monoterpenoid biosynthesis pathway and three in the terpenoid backbone biosynthesis pathway. Collectively, this genome-wide transcriptome provides a valuable tool for future identification of genes related to essential oil biosynthesis. Additionally, the identification of a cohort of genes in the biosynthetic pathways of terpenoids provides a theoretical basis for metabolic engineering of essential oils in C. camphora .

Citral chemotypes Cinnamomum camphora (C. camphora) and Cinnamomum bodinieri (C. bodinieri) are promising industrial plants that contain abundant citral. For a more in-depth study, their significant biological effect, the chemical composition and antioxidant capacity of essential oils of citral-rich chemotype C. camphora and C. bodinieri (EOCC) were determined in the present study. The EOCC yield, obtained by hydro-distillation and analyzed by gas chromatography–mass spectrometry (GC-MS), ranged from 1.45–2.64%. Forty components more than 0.1% were identified and represented, mainly by a high content of neral (28.6–39.2%), geranial (31.8–54.1%), Z-isocitral (1.8–3.2%), E-isocitral (3.2–4.7%), geraniol (1.3–2.6%) and caryophyllene (0.6–2.4%). The antioxidant properties of EOCC were estimated by DPPH, ABTS and FRAP methods. As our results indicated, the antioxidant activity was significantly correlated to oxygenated monoterpenes. The variety of C. bodinieri (N7) presented the best antioxidant profile, given its highest inhibition of DPPH radical (IC50 = 6.887 ± 0.151 mg/mL) and ABTS radical scavenging activity (IC50 = 19.08 ± 0.02 mg/mL). To the best of our knowledge, more than 88% citral of C. bodinieri was investigated and the antioxidant properties described for the first time. Considering high essential oil yield, rich citral content and high antioxidant activity, the N7 variety will be a good candidate for pharmaceutical and cosmetic development of an improved variety.