Leaf blade structure of Verbesina macrophylla (Cass.) F. S. Blake (Asteraceae): ontogeny, duct secretion mechanism and essential oil composition

Exploring the co-operativity of secretory structures for defense and pollination in flowering plants

MAIN CONCLUSION

In flowers multiple secretory systems cooperate to deliver specialized metabolites to support specific roles in defence and pollination. The collective roles of cell types, enzymes, and transporters are discussed. The interplay between reproductive strategies and defense mechanisms in flowering plants has long been recognized, with trade-offs between investment in defense and reproduction predicted. Glandular trichomes and secretory cavities or ducts, which are epidermal and internal structures, play a pivotal role in the secretion, accumulation, and transport of specialized secondary metabolites, and contribute significantly to defense and pollination. Recent investigations have revealed an intricate connection between these two structures, whereby specialized volatile and non-volatile metabolites are exchanged, collectively shaping their respective ecological functions. However, a comprehensive understanding of this profound integration remains largely elusive. In this review, we explore the secretory systems and associated secondary metabolism primarily in Asteraceous species to propose potential shared mechanisms facilitating the directional translocation of these metabolites to diverse destinations. We summarize recent advances in our understanding of the cooperativity between epidermal and internal secretory structures in the biosynthesis, secretion, accumulation, and emission of terpenes, providing specific well-documented examples from pyrethrum (Tanacetum cinerariifolium). Pyrethrum is renowned for its natural pyrethrin insecticides, which accumulate in the flower head, and more recently, for emitting an aphid alarm pheromone. These examples highlight the diverse specializations of secondary metabolism in pyrethrum and raise intriguing questions regarding the regulation of production and translocation of these compounds within and between its various epidermal and internal secretory systems, spanning multiple tissues, to serve distinct ecological purposes. By discussing the cooperative nature of secretory structures in flowering plants, this review sheds light on the intricate mechanisms underlying the ecological roles of terpenes in defense and pollination.

Chemical composition, chemotypic characterization, and histochemical localization of volatile components in different cultivars of Zanthoxylum bungeanum Maxim. leaves

Zanthoxylum bungeanum Maxim., an important spice plant, is rich in volatile components and has formed several cultivars in China. Genetic variation among different cultivars has significant effects on volatile components. In this study, a total of 52 volatile compounds were detected from 11 cultivars of Z. bungeanum, among which palmitic acid, (+)-limonene, phytol, β-caryophyllene, and terpinyl acetate were screened as characteristic compounds, with palmitic acid and phytol contributing the most to the volatile composition. Combined with the results of chemometric and content analyses, three Z. bungeanum chemotypes were identified: (+)-limonene, β-caryophyllene + terpinyl acetate, and palmitic acid + phytol. In addition, the dynamics of the accumulation of its main components were explored, and the optimal harvest period for Z. bungeanum leaves (late July or early August) was clarified. Moreover, histochemical analysis results showed that terpenoids were mainly accumulated in the oil cells of Z. bungeanum leaves, and there were some differences in the number of oil cells in different chemotypes of Z. bungeanum, which might affect the yield and quality of volatile components. The results showed that the differences of chemical composition among diverse chemotypes of Z. bungeanum might be an important factor leading to the quality differences of the same planting resources. Accordingly, the study on the classification of Z. bungeanum chemotypes and the accumulation patterns of major chemical components is of great theoretical significance and practical value as a favorable guarantee for the development and utilization of Z. bungeanum resources and quality control.

Structural and histochemical attributes of secretory ducts and cavities in leaves of four species of Calophyllaceae J. Agardh in Amazonian savannas

This study represents an important contribution to the structural, histochemical and biological understanding of ducts and cavities in leaves of four species of Calophyllaceae that occur in Amazonian savannas. Samples of adult leaves were processed using light, scanning and transmission electron microscopy, as per usual methods for plant anatomy. In paradermal sections, the lumina of ducts are elongated while those of cavities are short. Ducts occur exclusively in the central rib and are abundant in Kielmeyera rubriflora Cambess and Kielmeyera coriacea Mart. and Zucc and larger than in Calophyllum brasiliense Cambess and Caraipa densifolia Mart. In mesophyll, the type of secretory structure and distribution pattern of the ducts and cavities are distinct. In most species, the secreted metabolites are similar and consist of phenolic compounds, lipids, essential oils with oleoresins, mucilage, neutral polysaccharides, proteins and alkaloids, except in K. coriacea, which does not contain oleoresin. The secretion is probably synthesized by mitochondria, rough endoplasmic reticulum, ribosomes and dictyosomes and is externalized toward the lumen by granulocrine and eccrine processes. In addition to being of diagnostic value for species identification, the attributes of the lumen shape, type of secretory structure, distribution pattern, identified metabolites and secretion mechanism are important for understanding the biological roles of ducts and cavities. The identified metabolites reveal a capacity for adaptation, resistance and protection from the action of herbivores and pathogens, and in water retention.

The Volatile Phytochemistry of Seven Native American Aromatic Medicinal Plants

As part of our evaluation of essential oils derived from Native American medicinal plants, we have obtained the essential oils of Agastache foeniculum (Pursch) Kuntze (Lamiaceae), Gaultheria procumbens L. (Ericaceae), Heliopsis helianthoides (L.) Sweet (Asteraceae), Liatris spicata (L.) Willd. (Asteraceae), Pycnanthemum incanum (L.) Michx. (Lamiaceae), Smallanthus uvedalia (L.) Mack. ex Mack. (Asteraceae), and Verbena hastata L. (Verbenaceae) by hydrodistillation. The essential oils were analyzed by gas chromatographic techniques. The essential oil of A. foeniculum was dominated by estragole (88–93%), while methyl salicylate (91%) dominated the G. procumbens essential oil. Germacrene D was the major component in H. helianthoides (42%) and L. spicata (24%). 1,8-Cineole (31%) and α-terpineol (17%) were the main compounds in P. incanum essential oil. The essential oil of S. uvedalia showed α-pinene (24%), perillene (15%), and β-caryophyllene (17%) as major components. Verbena hastata essential oil was rich in 1-octen-3-ol (up to 29%) and palmitic acid (up to 22%). Four of these essential oils, H. helianthoides, L. spicata, P. incanum, and V. hastata, are reported for the first time. Additionally, the enantiomeric distributions of several terpenoid components have been determined.

The essential oil of the leaves of Verbesina macrophylla (Cass.) S.F.Blake has antimicrobial, anti-inflammatory and antipyretic activities and is toxicologically safe

ETHNOPHARMACOLOGICAL RELEVANCE

Verbesina macrophylla (Cass.) S.F.Blake is a medicinal plant from South America, popularly known as "asa de peixe", "asa de peixe branco", "cambará branco" or "cambará guaçu", being used by traditional communities for its healing powers in the form of teas, infusions, liqueurs and extracts, for the treatment of bacterial and fungal infections of the urinary and respiratory tracts, such as kidney problems, bronchitis, inflammation and fever. However, none of the ethnopharmacological properties has been scientifically evaluated.

AIM OF THE STUDY

Based on the ethnopharmacological use of the species, this study investigated the chemical composition, and for the first time acute toxicity, hemolytic, antimicrobial, anti-inflammatory and antipyretic activities of the essential oil from leaves of V. macrophylla.

MATERIAL AND METHODS

The essential oil was obtained from the leaves by hydrodistillation (HD), being characterized by gas chromatography coupled to mass spectrometry (GC-MS) and gas chromatography coupled to flame ionization detection (GC-FID). The antimicrobial activity was evaluated by the broth microdilution technique in bacteria and fungi that cause infections of the respiratory and urinary tract, and toxicological safety regarding hemolytic activity on human red blood cells (hRBCs), and acute toxicity in mice. The anti-inflammatory activity was evaluated by the model carrageenan-induced peritonitis with quantification of the levels of TNF-α and IL-1β in the intraperitoneal fluid, and ear edema induced by croton oil. The antipyretic activity evaluated in mice with pyrexia induced by yeast.

RESULTS

The extraction of essential oil by hydrodistillation (HD) showed a yield of 0.33 ± 0.04%, with its composition constituted mainly by sesquiterpenes of hydrocarbons (94.00%). The essential oil demonstrated antibacterial and antifungal activity, with a low rate of hemolysis in human red blood cells (hRBCs) and no clinical signs of toxicity were observed in animals after acute treatment, which suggested that the LD₅₀ is greater than 5000 mg/kg; p.o. The essential oil demonstrated anti-inflammatory activity reducing levels of pro-inflammatory cytokines TNF-α (38.83%, 72.42% and 73.52%) and IL-1β (37.70%, 75.92% and 87.71%), and ear edema by 49.53%, 85.04% and 94.39% at concentrations of 4, 40 and 400 mg/kg, respectively. The antipyretic activity presented by the essential oil is statistically similar to dipyrone.

CONCLUSION

The set of results obtained, validates the main activities attributed to the traditional use of Verbesina macrophylla (Cass.) S.F.Blake. These data add industrial value to the species, considering that the antimicrobial, anti-inflammatory and antipyretic activities present results similar to the drugs already used also presenting safety. The results suggest that essential oil from V. macrophylla may be used by industry for the development of drugs with natural antimicrobial, anti-inflammatory and antipyretic effect.

Verbesina crocata: A pharmacognostic study for the treatment of wound healing

Ethnopharmacological relevance

Verbesina crocata (Cav.) Less. (Arnica or Capitaneja) is an endemic plant from Mexico restricted to the western part of the country. The aerial parts are used in traditional medicine for the treatment of wounds and burns. The objective of this investigation was to carry out a pharmacognostic study of V. crocata and establish markers that allow for the recognition of the characteristics of the plant and validate its traditional use. The study includes anatomical and chemical characteristics of the plant as well as evaluations of its antioxidant capacity and wound healing ability in a murine model.

Materials and methods

An anatomical study of V. crocata was performed on the middle part of the leaf and stem. A methanolic extract of this species (VcME) was obtained by methanolic maceration of the aerial parts. Subsequently, a partition of the VcME was made to obtain a hexanic fraction (VcH). The phytochemical preliminary screening and characterization by high-performance liquid chromatography/mass spectrometry (HPLC-ESI/MS) of the VcME and VcH were performed. The antioxidant activity and total phenolic content were quantified. The wound healing capacity of the methanolic extract was determined in CD-1 mice by the healing rate, the tensiometric method, and histological analysis.

Results

The anatomical study of V. crocata showed the presence of two types of secretory structures and their position on the leaves. In addition, the characteristics of the middle vein and trichomes are potentially useful for recognition of the species. Chemical compounds detected by HPLC-ESI/MS reveal the presence of sitosterol glycoside and catechin derivatives as principal constituents of V. crocata. The VcME showed low antioxidant capacity and total phenolic. V. crocata had a similar healing effect to Recoveron® in the tensiometric method, but the rate of healing was higher. According to the histological analysis, the treatment of V. crocata promoted the remodelling phase 15 days after the incisional wound.

Conclusion

This is the first pharmacognostic study of this species that covers the plant anatomy, chemical content and biological properties related to its traditional use. V. crocata favours wound healing according to physical and histological evaluations. In addition, the characteristics of the middle vein, trichomes and catechin glycosides are potentially useful for the recognition of this species.