"Arnicas" from Brazil: comparative analysis among ten species

Abstract The "arnicas" found in Brazil are examples of different species of the family Asteraceae used in popular medicine for its attributed anti-inflammatory action. Among the species known and used as "arnica" we selected: Calea uniflora Less., Chaptalia nutans (L.) Polák, Lychnophora ericoides Mart., Lychnophora pinaster Mart., Lychnophora salicifolia Mart., Lychnophora diamantinana Coile & S.B.Jones, Porophyllum ruderale (Jacq.) Cass., Pseudobrickellia brasiliensis (Spreng.) R.M.King & H.Rob., Sphagneticola trilobata (L.) Pruski, and Solidago chilensis Meyen, due to their extensive use. This research provides new information on leaf morphology and anatomy and on chemistry of the major metabolites found in these species through histochemical tests and phytochemical review. The results revealed anatomical characters for the differentiation and quality control of the vegetal drugs, being these: distinctive epidermal attachments, epidermis cells, parenchymal cells of the mesophyll, vascular bundles, midvein patterns and secretory structures of exudation of secondary metabolites. The review of chemical profiles showed differences in the chemical composition of the species, as different skeletons of sesquiterpene lactones in the species evaluated in addition to other chemical classes such as terpenes, flavonoids, chromenes and phenolic acids derivate. Based on the results obtained in this work it is important to emphasize that the information about the ten species of arnica generate subsidies for differentiation and identification of characteristic markers and for the diagnosis of the species and it can be applied in the "arnicas" quality control.

Deep in the Jelly: Histochemical and Functional Aspects of Mucilage-Secreting Floral Colleters in the Orchids Elleanthus brasiliensis and E. crinipes.

Colleters are trichomes or emergencies that produce a sticky exudate consisting of a mixture of mucilage, lipids, terpenes, and phenolic compounds. Colleters occur in at least 60 families of angiosperms; however, reports of them are scarce for the Orchidaceae. Elleanthus brasiliensis is distinguished by the presence of an abundant gelatinous secretion that covers almost all of its inflorescences. We aimed to describe the histology of colleters in inflorescences of E. brasiliensis and Elleanthus crinipes, and to analyze the chemical composition of their secretion to better understand the functions of these secretory structures. Due to the low frequency of colleters and lack of visible secretion in E. crinipes, histochemical tests and chemical analyses were not performed for this species. Colleters are of a brush type and their secretion has, at the same time, hydrophilic and lipophilic components. Histochemical tests further revealed the presence of pectin, mucilage, lipids, terpenes, phenolic compounds, and proteins. The GC-MS analysis confirmed the presence of γ-sitosterol and palmitic, linoleic, and stearic acids in the secretion of E. brasiliensis. Infrared analysis indicated the possible presence of polysaccharides in the secretion. The occurrence of colleters in both species studied and in other orchids described in the literature suggests that these structures are common in the inflorescences of tropical orchids. In these environments, the hydrated polysaccharides in the secretion form a dense matrix that can act as a physical barrier, and terpenes may help to protect against herbivores and pathogenic microorganisms. This information broadens our knowledge of the morphological and chemical diversity of the secretions produced by orchid colleters.

A Mechanistic View of Interactions of a Nanoherbicide with Target Organism.

Atrazine is one of the most used herbicides and has been associated with persistent surface and groundwater contamination, and novel formulations derived from nanotechnology can be a potential solution. We used poly(ε-caprolactone) nanoencapsulation of atrazine (NC+ATZ) to develop a highly effective herbicidal formulation. Detailed structural study of interaction between the formulation and Brassica juncea plants was carried out with evaluation of the foliar uptake of nanoatrazine and structural alterations induced in the leaves. Following postemergent treatment, NC+ATZ adhered to the leaf and penetrated mesophyll tissue mainly through the hydathode regions. NC+ATZ was transported directly through the vascular tissue of the leaves and into the cells where it degraded the chloroplasts resulting in herbicidal activity. Nanocarrier systems, such as the one used in this study, have great potential for agricultural applications in terms of maintenance of herbicidal activity at low concentrations and a substantial increase in the herbicidal efficacy.

Trichomes related to an unusual method of water retention and protection of the stem apex in an arid zone perennial species.

It is well known that trichomes protect plant organs, and several studies have investigated their role in the adaptation of plants to harsh environments. Recent studies have shown that the production of hydrophilic substances by glandular trichomes and the deposition of this secretion on young organs may facilitate water retention, thus preventing desiccation and favouring organ growth until the plant develops other protective mechanisms. Lychnophora diamantinana is a species endemic to the Brazilian 'campos rupestres' (rocky fields), a region characterized by intense solar radiation and water deficits. This study sought to investigate trichomes and the origin of the substances observed on the stem apices of L. diamantinana. Samples of stem apices, young and expanded leaves were studied using standard techniques, including light microscopy and scanning and transmission electron microscopy. Histochemical tests were used to identify the major groups of metabolites present in the trichomes and the hyaline material deposited on the apices. Non-glandular trichomes and glandular trichomes were observed. The material deposited on the stem apices was hyaline, highly hydrophilic and viscous. This hyaline material primarily consists of carbohydrates that result from the partial degradation of the cell wall of uniseriate trichomes. This degradation occurs at the same time that glandular trichomes secrete terpenoids, phenolic compounds and proteins. These results suggest that the non-glandular trichomes on the leaves of L. diamantinana help protect the young organ, particularly against desiccation, by deposition of highly hydrated substances on the apices. Furthermore, the secretion of glandular trichomes probably repels herbivore and pathogen attacks.