Intraspecies diversity of the bioactive compounds of wild and cultivated Cinnamomum species in Sri Lanka

Cinnamomum verum has significant biochemical diversity across Sri Lanka, encompassing over 500 distinct chemotypes. Additionally, six wild relatives of Cinnamomum found in the region exhibit substantial morphological, genetic, and phytochemical variability, often shaped by their adaptation to isolated habitats. This research aims to explore the inter and intraspecies phytochemical diversity, volatile oil profiles, and environmental influences on wild Cinnamomum species, providing valuable insights for conservation, sustainable utilization, and breeding programs to enhance cinnamon's economic and ecological resilience. This study analyzed the inter and intraspecies diversity of six bioactive compounds in leaf and bark extracts using HPLC, the leaf volatile oil profiles (LVOP) through GCMS, and the leaf oil yield (LOY) of six wild Cinnamomum species. Samples were collected from at least two distinct agroecological zones, including both domesticated plots and natural habitats. HPLC analysis revealed that none of the species had detectable coumarin contents. Notably, C. sinharajaense from a domesticated plot in Matara presented significantly greater LOY (1.53%), leaf-eugenol content (30.38 mg/g), and bark-cinnamaldehyde content (8.20 mg/g) than its wild counterpart (Sinharaja forest: 0.32%, 4.99 mg/g and 1.67 mg/g). This performance was also superior to C. verum-wild and competitive with cultivated varieties. Cinnamomum capparu-coronde presented competitive bark-cinnamaldehyde levels at both locations (8.18/8.34 mg/g), with no significant difference, whereas its LVOP presented intraspecies variation in the relative abundances of eugenol (8.36/6.24%), benzyl benzoate (28.92/5.62%), bicyclogermacrene (5.54/19.77%), and gamma-muurolene (10.03/5.37%). GCMS analysis also revealed unique LVOPs for C. litseifolium, C. capparu-coronde, C. citriodorum, and C. dubium with high intraspecies diversity in terms of relative abundance, the total number of compounds, and prominent compounds. The intraspecies variability in leaf-eugenol, bark-cinnamaldehyde, and LVOP was correlated with the mean annual rainfall and temperature. The intraspecies biochemical diversity observed in C. sinharajaense, C. capparu-coronde, and C. dubium highlights their potential to adapt to diverse environmental conditions. Additionally, the observed inter- and intraspecies variations in all wild species emphasize the critical importance of conserving these underutilized cinnamon species through both ex-situ and in-situ conservation strategies.