Abstract
BackgroundThe oil and extracts of Lippia thymoides have been used for various medicinal and food applications. Entrepreneurs in the Amazon have been considering the economic exploitation of this plant. The present study evaluated the influence of the seasonal and circadian rhythm on the yield and composition of the essential oil of leaves and thin branches of a Lippia thymoides specimen cultivated in Abaetetuba, State of Pará, Brazil. The constituents of the oils were identified by GC and GC–MS and with the application of multivariate analysis: Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA).ResultsThe predominance of oxygenated monoterpenes (70.6–91.8%) was observed in oils, followed by monoterpene hydrocarbons (1.2 to 21.6%) and sesquiterpene hydrocarbons (3.9 to 9.1%). Thymol, thymol acetate, γ-terpinene, p-cymene, and (E)-caryophyllene were the first compounds. The mean thymol content was higher in the rainy season (seasonal: 77.0%; circadian: 74.25%) than in the dry period (seasonal: 69.9%; circadian: 64.5%), and it was influenced by climatic variables: rainfall precipitation, solar radiation, temperature, and relative humidity. For the circadian study, PCA and HCA analysis were applied to the constituents of oils from rainy and dry periods. Two groups were formed. A higher thymol content characterized the group 1, followed by (Z)-hexen-3-ol, α-thujene, α-pinene, α-phellandrene and humulene epoxide II, in minor percent. A higher content of p-cymene formed the group 2, γ-terpinene, thymol acetate and (E)-caryophyllene, followed by myrcene, α-terpinene, 1,8-cineole, terpinen-4-ol, methylthymol, and germacrene D, in a low percentage.ConclusionsThe different chemical profiles found in the oils of L. thymoides must be associated with the environmental conditions existing at its collection site. The knowledge of this variation in the oil composition is essential from the ecological and taxonomic point of view, regarding the management and economic use of the species.
Highlights
The oil and extracts of Lippia thymoides have been used for various medicinal and food applications
The present study evaluated the circadian and seasonal variation of the essential oil of a thymol rich specimen of Lippia thymoides, previously submitted to a cultivation test in the city of Abaetetuba, State of Pará, Brazil, intending to its future economic exploitation
The rational planting of L. thymoides can determine a better use for this species in the Amazon, with basis on the economic exploitation of the essential oil of some known chemical types
Summary
The predominance of oxygenated monoterpenes (70.6–91.8%) was observed in oils, followed by monoterpene hydrocarbons (1.2 to 21.6%) and sesquiterpene hydrocarbons (3.9 to 9.1%). Thymol acetate, γ-terpinene, p-cymene, and (E)-caryophyllene were the first compounds. The mean thymol content was higher in the rainy season (seasonal: 77.0%; circadian: 74.25%) than in the dry period (seasonal: 69.9%; circadian: 64.5%), and it was influenced by climatic variables: rainfall precipitation, solar radiation, temperature, and relative humidity. PCA and HCA analysis were applied to the constituents of oils from rainy and dry periods. A higher thymol content characterized the group 1, followed by (Z)-hexen-3-ol, α-thujene, α-pinene, α-phellandrene and humulene epoxide II, in minor percent. A higher content of p-cymene formed the group 2, γ-terpinene, thymol acetate and (E)-caryophyllene, followed by myrcene, α-terpinene, 1,8-cineole, terpinen-4-ol, methylthymol, and germacrene D, in a low percentage
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