RESUMO
Selenium is a micronutrient with a wide range of functions in animals, including humans, and in microorganisms such as microalgae. However, its role in plant metabolism remains ambiguous. Recent studies of Se supplementation showed that not only does it increase the content of the element itself, but also affects the accumulation of secondary metabolites in plants. The purpose of this review is to analyze and summarize the available data on the place of selenium in the secondary metabolism of plants and its effect on the accumulation of some plant metabolites (S- and N-containing secondary metabolites, terpenes, and phenolic compounds). In addition, possible molecular mechanisms and metabolic pathways underlying these effects are discussed. It should be noted that available data on the effect of Se on the accumulation of secondary metabolites are inconsistent and contradictory. According to some studies, selenium has a positive effect on the accumulation of certain metabolites, while other similar studies show a negative effect or no effect at all. The following aspects were identified as possible ways of regulating plant secondary metabolism by Se-supplementation: changes occurring in primary S/N metabolism, hormonal regulation, redox metabolism, as well as at the transcriptomic level of secondary metabolite biosynthesis. In all likelihood, the confusion in the results can be explained by other, more complex regulatory mechanisms in which selenium is involved and which affect the production of metabolites. Further study on the involvement of various forms of selenium in metabolic and signaling pathways is crucial for a deeper understanding of its role in growth, development, and health of plants, as well as the regulatory mechanisms behind them.
RESUMO
From an economic and ecological standpoint, it is crucial to investigate the biologically active compounds of mistletoe plants, which are currently discarded by pruning urban mistletoe-infested trees. In the present study, the content of phenolic compounds, triterpenic and organic acids, as well as the antioxidant activity of the extracts of various mistletoe organs (leaves, stems, and fruits) collected from the most infested tree species were investigated. The mistletoe samples collected from Betula pendula, Acer platanoides, Crataegus monogyna, and Sorbus aucuparia showed the highest content of phenolic acids and flavonoids as well as antioxidant activity, as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing/antioxidant power (FRAP) assays. The leaves and stems of mistletoe from Tilia cordata were characterized by a high content of triterpenic acids (oleanolic, ursolic, and betulinic). The leaves and fruits of mistletoe plants from Populus nigra and Salix alba contained a high concentration of organic acids, particularly succinic and citric acids. Compared to stem and leaf extracts, the antioxidant activity of the mistletoe fruit extracts was 1.5-3 times higher. The obtained results indicate that mistletoe is a valuable raw material and can be used as a source of phenolic compounds and triterpenic and organic acids, as well as for producing extracts with antioxidant properties.
RESUMO
BACKGROUND: The Lamiaceae family, one of the most important herbaceous and shrub plant families, includes a wide variety of plants with biological and medicinal uses. This study aimed to conduct a comparative analysis of phenolic compounds content and biological activity of extracts from eight species of Lamiaceae plants, cultivated in a temperate climate, and to study the effect of the foliar salicylic acid application on these parameters. METHODS: Lamiaceae plants (Lavandula angustifolia, Salvia officinalis, Hyssopus officinalis, Agastache foeniculum, Thymus serpyllum, Mentha × piperita, Origanum vulgare, Monarda didyma) cultivated on field experimental sites. Plants were sprayed with salicylic acid at a concentration of 1 mM. The untreated with salicylic acid plants were used as control. RESULTS: The highest contents of hydroxycinnamic acids and flavonoids in control plants were observed in the Agastache foeniculum (6.4 ± 0.6 mg g-1 and 6.5 ± 0.4 mg g-1 respectively). The highest content of phenolic compounds was found in Monarda didyma (13.8 ± 0.7 mg g-1). Among the control plants, Agastache foeniculum, Hyssopus officinalis, and Mentha × piperita were characterized by the highest antioxidant activity. All the studied extracts had the ability to inhibit α-amylase and α-glucosidase. Significant positive correlations were revealed between the antioxidant activity and the contents of hydroxycinnamic acids, total phenolic compounds, and flavonoids. A high degree of correlation was found between the α-amylase inhibitory activity and the content of hydroxycinnamic acids (r = 0.72, p ≤ 0.05), as well as between the α-glucosidase inhibitory activity and the content of flavonoids (r = 0.83, p ≤ 0.05) and hydroxycinnamic acids (r = 0.81, p ≤ 0.05). The foliar treatment with salicylic acid led to an increase in the contents of hydroxycinnamic acids (in 6 species), flavonoids (in 2 species), total phenolic compounds (in 7 species), antioxidant activity (in 5 species), as well as in α-amylase (in 4 species) and α-glucosidase (in 5 species) inhibitory activity compared to the control plants. Lavandula angustifolia was the most susceptible to foliar treatment with salicylic acid. In this plant species, a significant increase in all studied biochemical parameters was noted. CONCLUSIONS: The results obtained on the stimulating effects of salicylic acid can be used to increase the nutritional and pharmacological value of plants of the Lamiaceae family cultivated in temperate climates.
