Abstract
The present study aimed to determine seasonal influences on the physiological characteristics of G. brasiliensis that are associated with the production of secondary metabolites, as well as the yield and composition of leaf essential oil (EO). We evaluated leaves of six-year-old plants at four cardinal points in the middle third of a canopy with four replicates during May, August, November, and February. There were assessed photosynthesis rate, total phenolic and total flavonoid contents, phenylalanine (PAL) and tyrosine (TAL) ammonia-lyase activities and the leaves were histochemically stained. We quantified isolated phenolic compounds from leaf methanolic and hexanic extracts. The EO yield and composition, and the numbers and diameters of oil secretory channels in leaves were also evaluated. The photosynthetic rate peaked during November, whereas the total phenolic content and PAL and TAL activities peaked in February. Phenolic compounds were dispersed in the central rib and limbus in idioblasts. Only morelloflavone (fukugetin) was detected in methanolic extracts, and the concentration in leaves peaked during November. The yield and composition of the EO varied with the seasons, and the EO yield was maximal during November. Sesquiterpenes were the main components in the leaf EO. Our findings indicate that spring is the most suitable season for obtaining morelloflavone and a higher yield of EO from G. brasiliensis leaves in tropical regions.
Published Version
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