Morfoanatomia de pecíolos, perfil químico sazonal e atividade biológica dos óleos essenciais de seis espécies de Eucalyptus L’ HÉR (Myrtaceae)

Abstract

Eucalyptus stands out as the most cultivated globally within the Myrtaceae family, with notable morphological similarity. It presents growing economic importance due to the essential oils (EOs) produced, which are attributed to diverse biological activities. This study aimed to investigate the petiolar morphoanatomy, phytochemistry and biological activities of essential oils from leaves of six Eucalyptus species, namely: E. badjensis, E. benthamii, E. dunnii, E. grandis, E. globulus and E. saligna, collected seasonally (spring, summer, autumn and winter). Cultivation conditions and plant development stage were standardized for all species. The morphoanatomy was analyzed using standard microscopy methods. The EOs from the leaves were extracted by hydrodistillation. The chemical profile was determined by GC-EM and CCDAE and the

biological activities were tested for insecticidal (topical and fumigation) and anti- inflammatory action (carrageenan-induced paw edema, mechanical hyperalgesia,

sensitivity to cold and pleurisy). The morphoanatomical study of the petioles highlighted the following differences: size, cross-sectional shape, size of cavities, arrangement, and number of vascular bundles, in addition to crystalline morphotypes. The essential oils of the six species showed significant variations in the content, chemical constitution and concentration of volatile compounds depending on seasonality. Yields varied between 0.7-2.43%, being the highest for E. badjensis in summer and the lowest for E. grandis in winter. The major constituents were in E. badjensis (1,8-cineole), E. benthamii (α-pinene and globulol), E. dunnii (α-pinene and 1,8-cineole), E. globulus (1,8- cineole), E. grandis (α-pinene and o-cymene) and E. saligna (o-cymene and cryptone). High-performance thin-layer chromatography has emerged as a rapid technique for monitoring chemical composition. GC-MS and CCDAE analyzes showed that different Eucalyptus had unique chemical compositions. This finding was demonstrated in principal components cluster analysis. Insecticide analysis revealed that E. benthamii EO is the most potent against Cimex lectularius. The six EOs demonstrated antioxidant activity in the ABTS model. EOs from E. benthamii, E. dunnii and E. grandis showed significant anti-inflammatory activities in tested experimental models. These findings highlight the importance of studying Eucalyptus essential oils, not only for their chemical diversity and therapeutic potential but also for their seasonal variability and specificity between species as illustrated in the anatomical study.