Abstract
In this study, we aimed to determine whether seasonality affects the content, chemical composition, and antimicrobial activity of essential oils (EOs) from the leaves of three species of Nectandra (Nectandra megapotamica, Nectandra grandiflora, and Nectandra lanceolata) native to the Atlantic rainforest, Sao Paulo state, Brazil. In addition, we identified the compounds potentially related to the antimicrobial activity. Leaves were randomly collected in the middle of winter (August), spring (November), summer (February), and autumn (May). The influence of seasonality on the content and chemical composition of EOs from the Nectandra species was evident in this study. The EOs from N. lanceolata and N. grandiflora were characterized by similarities in the chemical composition and had a higher relative proportion of oxygenated sesquiterpenes. N. megapotamica presented a different chemical profile, with plenty of monoterpenic and sesquiterpenic hydrocarbons. Changes in the EO chemical profile because of seasonality were shown by the similarities between the EOs obtained in spring and autumn and the differences between the EOs obtained in summer and winter. The EO from the leaves of N. megapotamica harvested in winter and spring showed the highest control of the growth of Escherichia coli, and this antimicrobial action can be related to the monoterpenes α-pinene and β-pinene as well as myrcene and limonene. The minimum inhibitory concentration (MIC) of the EO from the leaves of N. lanceolata harvested in summer and autumn was lower against the gram-positive bacterium Staphylococcus aureus and can be related to the sesquiterpene hydrocarbons isobicyclogermacrenal, epi-zizanone, and germacrene B.
Highlights
The genus Nectandra has a great diversity of essential oil (EO) constituents that may be influenced by seasonality; biome diversity; and plant age, part, and developmental stage [1,2]
These two species were characterized by their similar EO chemical compositions, whereas N. megapotamica had a distinct chemical profile, constituted a separate class, and did not show variations in the EO content
Alterations to the EO chemical profile with seasonality were observed, and class 1 was formed by the EO of leaves harvested in summer; class 2, EO of leaves collected in winter; class 3, EO of leaves harvested in spring and autumn
Summary
The genus Nectandra (family, Lauraceae) has a great diversity of essential oil (EO) constituents that may be influenced by seasonality; biome diversity; and plant age, part, and developmental stage [1,2]. Several environmental and climatic factors, such as atmospheric pollution, solar irradiation, soil, and water availability, as well as factors inherent to the plant may induce variations in the composition of secondary metabolites [3]. All these factors associated with harvest time are important and should be considered when assessing active plant compounds. EOs from other Lauraceae species (Lindera pulcherrima, Dodecadenia grandiflora, and Persea gamblei) were studied, and they showed antibacterial effects against S. aureus and Pasteurella multocida; only the EO from Persea gamblei proved to be efficient against E. coli [7]. We verified the chemical similarities of the EO by performing multivariate analysis, to identify compounds potentially related to antibacterial activity
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