Altitudinal variation of UV-absorbing compounds in Plantago asiatica

Plant-Derived Caffeic Acid and Its Derivatives: An Overview of Their NMR Data and Biosynthetic Pathways

In recent years, caffeic acid and its derivatives have received increasing attention due to their obvious physiological activities and wide distribution in nature. In this paper, to clarify the status of research on plant-derived caffeic acid and its derivatives, nuclear magnetic resonance spectroscopy data and possible biosynthetic pathways of these compounds were collected from scientific databases (SciFinder, PubMed and China Knowledge). According to different types of substituents, 17 caffeic acid and its derivatives can be divided into the following classes: caffeoyl ester derivatives, caffeyltartaric acid, caffeic acid amide derivatives, caffeoyl shikimic acid, caffeoyl quinic acid, caffeoyl danshens and caffeoyl glycoside. Generalization of their 13C-NMR and 1H-NMR data revealed that acylation with caffeic acid to form esters involves acylation shifts, which increase the chemical shift values of the corresponding carbons and decrease the chemical shift values of the corresponding carbons of caffeoyl. Once the hydroxyl group is ester, the hydrogen signal connected to the same carbon shifts to the low field (1.1~1.6). The biosynthetic pathways were summarized, and it was found that caffeic acid and its derivatives are first synthesized in plants through the shikimic acid pathway, in which phenylalanine is deaminated to cinnamic acid and then transformed into caffeic acid and its derivatives. The purpose of this review is to provide a reference for further research on the rapid structural identification and biofabrication of caffeic acid and its derivatives.

Effects of UV-B radiation on pollen germination and tube growth: A global meta-analysis

Despite widespread recognition of pollen's potential sensitivity to ultraviolet-B (UV-B) radiation (280-315 nm), there remains ongoing debate surrounding the extent and mechanisms of this effect. In this study, using published data on pollen germination and tube growth including 377 pair-wise comparisons from 77 species in 30 families, we present the first global quantification of the effects of UV-B radiation on pollen germination and tube growth, along with its underlying mechanisms. Our results showed a substantial reduction in both pollen germination and tube growth in response to UV-B radiation, affecting 90.9 % and 84.2 % of species, respectively. Notably, these reductions exhibited phylogenetic constraints, highlighting the role of evolutionary history in shaping the sensitivity of pollen germination and tube growth to UV-B radiation. A negative correlation between elevation and the sensitivity of pollen tube growth was detected, suggesting that pollens from plants at higher elevations exhibit greater resistance to UV-B radiation. Our investigation also revealed that the effects of UV-B radiation on pollen germination and tube growth were influenced by a range of abiotic and biotic factors. Nevertheless, the intensity and duration of UV-B radiation exposure exhibited the highest explanatory power for the effects on both pollen germination and tube growth. This suggests that the responses of pollens to UV-B radiation are profoundly influenced by its dose, a critical consideration within the context of global change. In conclusion, our study provides valuable insights into the diverse responses of pollen germination and tube growth to UV-B radiation, highlighting the environment and species-dependent nature of pollen's susceptibility to UV-B radiation, with substantial implications for our understanding of the ecological and agricultural consequences of ongoing changes in UV-B radiation.

Urban Flora Riches: Unraveling Metabolic Variation Along Altitudinal Gradients in Two Spontaneous Plant Species

Using resilient, self-sustaining plants in urban green spaces enhances environmental and cultural benefits and reduces management costs. We assessed two spontaneous plant species, Linaria vulgaris Mill. and Cichorium intybus L., in four sites from the surrounding urban areas, ranging in altitude from 78 to 1040 m. Protection against UV-B radiation is crucial for plants at higher altitudes, guiding our focus on UV-visible absorption spectra, fluorometric emission spectra, secondary metabolite accumulation, and pigment dynamics in leaves. Our findings revealed a slight increase in UV-absorbing compounds with altitude and species-specific changes in visible spectra. The UV-emission of fluorochromes decreased, while red emission increased with altitude but only in chicory. Polyphenols and flavonoids showed a slight upward trend with altitude. Divergent trends were observed in condensed tannin accumulation, with L. vulgaris decreasing and C. intybus increasing with altitude. Additionally, chicory leaves from higher altitudes (792 and 1040 m) contained significantly lower triterpene concentrations. In L. vulgaris, chlorophyll pigments and carotenoids varied with sites, contrasting with UV absorbance variations. For C. intybus, pigment variation was similar to absorbance changes in the UV and VIS range, except at the highest altitude. These observations provide valuable insights into species-specific strategies for adapting to diverse environmental contexts.

Flavonoids and phenylethanoids from the flowers and leaves of Aeschynanthus species and cultivars (Gesneriaceae)

Forty-one flavones, each one of flavonol, chalcone and dihydroflavonol, two flavanones, and four phenylethanoids were isolated from corollas, calyces and leaves of two Aeschynanthus species, A. fulgens and A. pulcher, and six cultivars, 'Mahligai', 'Mona Lisa', SoeKa', 'Redona', 'Freshya' and 'Bravera'. Flavonoids were mainly the glucuronides and/or methylglucuronides based on hispidulin, nepetin, pectolinarigenin, 6-hydroxyluteolin, scutellarein, apigenin and luteolin, and identified by UV spectra, HR-MS, LC-MS, acid hydrolysis, NMR, and/or HPLC and TLC comparisons with authentic samples. Of these flavonoids, twelve, i.e. hispidulin 7,4'-di-O-glucuronide, 7,4'-di-O-methylglucuronide, 7-O-methylglucuronide-4'-O-glucuronide, 7-O-glucuronide-4'-O-methylglucuronide, 7-O-glucosyl-(1 → 2)-glucuronide and 8-C-glucoside, nepetin 7,4'-di-O-glucuronide, 7-O-glucuronide-4'-O-methylglucuronide and 7-O-methylglucuronide-4'-O-glucuronide, pectolinarigenin 7-O-glucosyl-(1 → 2)-glucuronide and 7-O-xylosyl-(1 → 2)-(6″-malonylglucoside), and 6-hydroxyluteolin 7,4'-di-O-glucuronide, were previously undescribed.

Flavonoids metabolism and physiological response to ultraviolet treatments in Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diels et Gilg is a folk herb in Zhejiang Province with anti-inflammatory, antineoplastic, and anti-oxidation effects. Given its pharmacological activity, T. hemsleyanum is known as New "Zhebawei" and included in the medical insurance system of Zhejiang and other provinces. Flavonoids are the most important components of T. hemsleyanum, and their contents are mainly regulated by ultraviolet (UV) radiation. In this study, the total flavonoid contents, flavonoid monomer contents, and flavonoid synthesis related enzyme activities (phenylalanine ammonia-lyase, chalcone synthase, and chalcone isomerase), anti-oxidant enzyme activities (catalase, peroxidase, and superoxide dismutase), and biochemical indicators (malondialdehyde, free amino acid, soluble protein, and soluble sugar) in the leaves (L) and root tubers (R) of T. hemsleyanum with UV treatments were determined. Three kinds of UV radiation (UV-A, UV-B, and UV-C) and six kinds of radiation durations (15 and 30 min, 1, 2, 3, and 5 h) were used. Appropriate doses of UV-B and UV-C radiation (30 min to 3 h) induced eustress, which contributed to the accumulation of flavonoids and improve protective enzyme system activities and bioactive compound contents. Especially, certain results were observed in several special structures of the flavonoid monomer: quercetin contents in L increased by nearly 20 times, isoquercitrin contents in R increased by nearly 34 times; most of flavonoids with glycoside content, such as quercitrin (19 times), baicalin (16 times), and apigenin-7G (13 times), increased multiple times. Compared with the CK group, the flavonoid synthase activities, anti-oxidant enzyme activities, and biochemical substance contents in L and R all increased with UV treatments. This study provides a theoretical foundation for regulating flavonoids by light factors and improving the quality of T. hemsleyanum in production and medical industries.

Who will win where and why? An ecophysiological dissection of the competition between a tropical pasture grass and the invasive weed Bracken over an elevation range of 1000 m in the tropical Andes

In tropical agriculture, the vigorously growing Bracken fern causes severe problems by invading pastures and out-competing the common pasture grasses. Due to infestation by that weed, pastures are abandoned after a few years, and as a fatal consequence, the biodiversity-rich tropical forest is progressively cleared for new grazing areas. Here we present a broad physiological comparison of the two plant species that are the main competitors on the pastures in the tropical Ecuadorian Andes, the planted forage grass Setaria sphacelata and the weed Bracken (Pteridium arachnoideum). With increasing elevation, the competitive power of Bracken increases as shown by satellite data of the study region. Using data obtained from field measurements, the annual biomass production of both plant species, as a measure of their competitive strength, was modeled over an elevational gradient from 1800 to 2800 m. The model shows that with increasing elevation, biomass production of the two species shifts in favor of Bracken which, above 1800 m, is capable of outgrowing the grass. In greenhouse experiments, the effects on plant growth of the presumed key variables of the elevational gradient, temperature and UV radiation, were separately analyzed. Low temperature, as well as UV irradiation, inhibited carbon uptake of the C4-grass more than that of the C3-plant Bracken. The less temperature-sensitive photosynthesis of Bracken and its effective protection from UV radiation contribute to the success of the weed on the highland pastures. In field samples of Bracken but not of Setaria, the content of flavonoids as UV-scavengers increased with the elevation. Combining modeling with measurements in greenhouse and field allowed to explain the invasive growth of a common weed in upland pastures. The performance of Setaria decreases with elevation due to suboptimal photosynthesis at lower temperatures and the inability to adapt its cellular UV screen.

Untargeted metabolic profiling reveals geography as the strongest predictor of metabolic phenotypes of a cosmopolitan weed

Plants produce a multitude of metabolites that contribute to their fitness and survival and play a role in local adaptation to environmental conditions. The effects of environmental variation are particularly well studied within the genus Plantago; however, previous studies have largely focused on targeting specific metabolites. Studies exploring metabolome-wide changes are lacking, and the effects of natural environmental variation and herbivory on the metabolomes of plants growing in situ remain unknown. An untargeted metabolomic approach using ultra-high-performance liquid chromatography-mass spectrometry, coupled with variation partitioning, general linear mixed modeling, and network analysis was used to detect differences in metabolic phenotypes of Plantago major in fifteen natural populations across Denmark. Geographic region, distance, habitat type, phenological stage, soil parameters, light levels, and leaf area were investigated for their relative contributions to explaining differences in foliar metabolomes. Herbivory effects were further investigated by comparing metabolomes from damaged and undamaged leaves from each plant. Geographic region explained the greatest number of significant metabolic differences. Soil pH had the second largest effect, followed by habitat and leaf area, while phenological stage had no effect. No evidence of the induction of metabolic features was found between leaves damaged by herbivores compared to undamaged leaves on the same plant. Differences in metabolic phenotypes explained by geographic factors are attributed to genotypic variation and/or unmeasured environmental factors that differ at the regional level in Denmark. A small number of specialized features in the metabolome may be involved in facilitating the success of a widespread species such as Plantago major into such wide range of environmental conditions, although overall resilience in the metabolome was found in response to environmental parameters tested. Untargeted metabolomic approaches have great potential to improve our understanding of how specialized plant metabolites respond to environmental change and assist in adaptation to local conditions.

Influence of altitude and enhanced ultraviolet-B radiation on tuber production, seed viability, leaf pigments and morphology in the wild potato species Solanum kurtzianum Bitter & Wittm collected from an elevational gradient

Climate change could lead to an upward shift in plant distribution, exposing populations to higher levels of ultraviolet (UV)-B radiation. In the framework of an in situ strategy for conserving potato wild relatives, we evaluated the effect of high UV-B levels on natural population of Solanum kurtzianum. The hypothesis is that plants from naturally higher altitudes are more adapted to increased UV-B radiation. Two populations from low and high altitudes were field supplemented using UV-B-lamps (+UV-B) or excluded from it with plastic filters. Additionally, to assess in which extent the plant responses to these artificial experimental conditions are reproducible in natural conditions, three genotypes were cultivated in two mountain experimental gardens (EG) at different elevations. +UV-B treatment induced changes in leaf morphology and increases in phenolic compounds in both populations, indicating plant adaptation, since chlorophylls and reproductive structures were not negatively affected. These results indicate that this environmental factor may not limit the displacement of populations towards sites with higher UV-B levels. Meanwhile, in higher-altitude EG a tubers yield reduction, mainly through a decreased tuber number and a bigger accumulation of phenolic compounds than in +UV-B treatment were observed, suggesting that UV-B is not the only factor involved in plants adaptation to high altitude environments.

Arabidopsis thaliana natural variation reveals connections between UV radiation stress and plant pathogen-like defense responses

UV radiation is a ubiquitous component of solar radiation that affects plant growth and development. Here we studied growth related traits of 345 Arabidopsis thaliana accessions in response to UV radiation stress. We analyzed the genetic basis of this natural variation by genome-wide association studies, which suggested a specific candidate genomic region. RNA-sequencing of three sensitive and three resistant accessions combined with mutant analysis revealed five large effect genes. Mutations in PHE ammonia lyase 1 (PAL1) and putative kinase At1g76360 rendered Arabidopsis hypersensitive to UV stress, while loss of function from putative methyltransferase At4g22530, novel plant snare 12 (NPSN12) and defense gene activated disease resistance 2 (ADR2) conferred higher UV stress resistance. Three sensitive accessions showed strong ADR2 transcriptional activation, accumulation of salicylic acid (SA) and dwarf growth upon UV stress, while these phenotypes were much less affected in resistant plants. The phenotype of sensitive accessions resembles autoimmune reactions due to overexpression of defense related genes, and suggests that natural variation in response to UV radiation stress is driven by pathogen-like responses in Arabidopsis.

Allelopathic Potential of Invasive Plantago virginica on Four Lawn Species

Plantago virginica L. has invaded many lawn ecosystems in the Eastern part of China. The invasion has incurred an economic cost to remove them. In order to prevent the invasion, it is critical to understand the invasive mechanisms of this species. However, few studies have been conducted on the allelopathic mechanisms of its invasion. In this study, we examined allelopathic effects of P. virginica on germination of seeds and growth of seedlings of four widely used lawn species. We found extensive allelopathic potential of P. virginica on other lawn species, which varied with species and developmental stage. While most effects of the extracts of P. virginica were inhibitory, some variables in some species were promoted by the addition of the extracts. The extracts of P. virginica significantly inhibited seed germination of Agrostis matsumurae. While the overall differences in seed germination rate of Poa annua were significant among treatments, difference between control and any of the treatments was not significant. The height of seedlings of A. matsumurae and Cynodon dactylon was significantly lower under the treatments of adding extracts of P. virginica. In contrast, growth of seedlings of Festuca elata and P. annua did not show significant differences among treatments. The root length of A. matsumurae, C. dactylon and P. annua was suppressed by the extracts of P. virginica whereas root length of F. elata was not affected. Aboveground biomass of A. matsumurae and F. elata was significantly higher than control, except for F. elata at the concentration of 50mg/mL, whereas aboveground biomass of C. dactylon and P. annua was reduced at higher concentrations of the extracts. Except for A. matsumurae, root biomass of the other three lawn species declined under the treatments with the extracts of P. virginica. Our results revealed that P. virginica had allelopathic potential on four lawn species and supported the theory of "novel weapons hypothesis". Invasion by P. virginica in lawn can be moderated by selecting those species that are not affected or promotionally affected by it.

Flavonoids and their Qualitative Variation in Calystegia soldanella and Related Species (Convolvulaceae)

Coastal species are exposed to severe environmental stresses, e.g. salt and UV-B. The plants adapt themselves to such harsh environment by controlling morphological features and chemical defense systems. Flavonoids are known as efficient anti-stress polyphenols produced by plants. Most flavonoids show antioxidant activity, and their properties are important for plants to survive under high-stress conditions such as those in a coastal area. Among the compounds, ortho-dihydroxylated flavonoids act as strong antioxidants. In this survey, we elucidated the flavonoid composition of a seashore species Calystegia soldanella, which is distributed not only on the seashore, but also by the inland freshwater lake, Lake Biwa. Seven flavonol glycosides, i.e. quercetin 3- O-rutinoside, 3- O-glucoside, 3- O-rhamnoside and 3- O-apiosyl-(1→2)-[rhamnosyl-(1→6)-glucoside], and kaempferol 3- O-rutinoside, 3- O-glucoside and 3- O-rhamnoside were isolated from the leaves of C. soldanella. In addition, it was shown that the quercetin (Qu) to kaempferol (Km) ratio of coastal populations was higher than that of lakeshore populations. In general, these differences of Qu/Km ratio depend on flavonoid 3′-hydroxylase (F3′H) transcription. RT-PCR analysis suggested that F3′H of C. soldanella is regulated translationally or post-translationally, but not transcriptionally. Furthermore, quantitative and qualitative differences in flavonoid composition occurred among three Calystegia species, C. soldanella, C. japonica and C. hederacea.

Altitudinal Variation of Flavonoid Content in the Leaves of Fallopia japonica and the Needles of Larix kaempferi on Mt. Fuji

Ultraviolet-B radiation is harmful to plants, and its intensity increases at altitude. So plants growing at high altitude possess UV protection systems. Flavonoid is known as a major UV protectant because it absorbs UV radiation and scavenges UV-induced free radicals in plant tissues. Japanese knotweed ( Fallopia japonica) and Japanese larch ( Larix kaempferi) grow at a wide range of altitudes on Mt. Fuji, the highest mountain in Japan, while the two plants harbor a homogeneous genetic structure. In the present study, a total of 14 flavonol 3- O-glycosides were isolated from both species. Furthermore, quantitative HPLC analyses revealed that flavonoid levels in the leaves of F. japonica and the needles of L. kaempferi increased with increasing altitude of their growing sites. The altitudinal trend of UV-absorbing antioxidants of herbal and woody plants was simultaneously revealed for the first time. These results suggest that both species have chemically acclimatized to high altitude regions, in which severe environmental conditions such as higher UV radiation exist.

Foliar Flavonoids from Tanacetum vulgare var. boreale and their Geographical Variation

Foliar flavonoids of Tanacetum vulgare var. boreale were isolated. Eight flavonoid glycosides, 7- O-glucosides of apigenin, luteolin, scutellarein and 6-hydroxyluteolin, and 7- O-glucuronides of apigenin, luteolin, chrysoeriol and eriodictyol were identified. Moreover, eight flavonoid aglycones, apigenin, luteolin, hispidulin, nepetin, eupatilin, jaceosidin, pectolinarigenin and axillarin were also isolated and identified. The flavonoid composition of two varieties of T. vulgare, i.e. var. boreale and var. vulgare, were compared. All samples of var. boreale and one sample of var. vulgare had the same flavonoid pattern, and could be distinguished from almost all the samples of var. vulgare. Thus, the occurrence of chemotypes, which are characterized by either the presence or absence of scutellarein 7- O-glucoside, eriodictyol 7- O-glucuronide and pectolinarigenin was shown in T. vulgare sensu lato.

Altitudinal and seasonal changes of phenolic compounds in Buxus sempervirens leaves and cuticles

The variation in the leaf content of phenolic compounds has been related to the UV-B changes of the environment in which plants grow. In this context, we aimed to investigate: a) whether the seasonal and altitudinal changes in the content of phenolic compounds of Buxus sempervirens L. leaves and cuticles could be related to the natural fluctuations in UV-B levels and b) the possible use of specific phenolic compounds as biomarkers of ambient UV-B levels. To achieve these goals we sampled, every three months during one year, leaves of B. sempervirens along an altitudinal gradient. At the lowest and the highest altitudes, we also conducted a UV-exclusion experiment to discern whether the observed changes could be attributed to the natural variation in UV-B. Results show that total phenolic content of leaves was lower in June than in the other sampling dates, which suggests a leaf ontogenic rather than a UV-B effect on the leaf content of these compounds. Regarding the elevational gradient, the overall amount of phenolic acids and neolignan of entire leaves increased with altitude while the total amount of flavonoids in leaf cuticles decreased. However, the lack of a significant effect of our UV-exclusion treatment on the content of these compounds suggests that the observed variations along the altitudinal gradient would respond to other factors rather than to UV-B. Concomitantly, we did not find any phenolic compound in leaves or cuticles of B. sempervirens that could be considered as a biomarker of ambient UV-B levels.

Identification and quantification of phytochemical composition and anti-inflammatory, cellular antioxidant, and radical scavenging activities of 12 Plantago species

Twenty-eight seed samples of 12 Plantago species were investigated for their chemical compositions and anti-inflammatory, cellular antioxidant, and radical scavenging properties. A new UPLC-UV procedure was developed and applied to quantify acteoside and geniposidic acid, the characteristic constituents of the genus Plantago. The amounts of acteoside and geniposidic acid ranged from 0.07 to 15.96 mg/g and from 0.05 to 10.04 mg/g in the tested samples, respectively. Furthermore, 26 compounds were tentatively identified by UPLC/Q-TOF-MS analysis. The Plantago samples significantly differed in their phytochemical compositions. The extracts of Plantago seeds also showed inhibitory effects on LPS-induced IL-1β, IL-6, and COX-2 mRNA expression in RAW 264.7 mouse macrophage cells. Additionally, significant variations were observed among different samples on cellular antioxidant activities in HepG2 cells, as well as DPPH and hydroxyl radical scavenging capacities. The results from this study may be used to promote the use of the genus Plantago in improving human health.

Chemical Profile, Radical Scavenging and Cytotoxic Activity of Yellow Gentian Leaves (Genitaneae Luteae Folium) Grown in Northern Regions of Montenegro

LC-ESI-MS and HPLC were used for the identification of the constituents from G. lutea leaves collected at different localities, as well as for quantification of the main compounds. Seven secoiridoids, five C-glucoflavones and three xanthones, were identified. Swertiamarin derivatives, namely eustomorusside (2), eustomoside (3) and septemfidoside (5), were detected in G. lutea for the first time. Concentrations of five constituents (swertiamarin, gentiopicrin, isovitexin, mangiferin and isogentisin) were determined. The relationship between concentrations of γ-pyrones and altitude was observed with statistically significant correlation ( r = 0.94). The extracts were also evaluated for their content of total phenolics, and antiradical and cytotoxic activities. The total phenolics content ranged from 7.7 to 12.7 mg GAE/g, and the IC50 values for DPPH radical scavenging activity varied between 0.45 to 2.02 mg/mL. The leaf extract exhibited moderate cytotoxic effects toward HeLa cells with an IC50 value of 41.1 μg/mL, while gentiopicrin, mangiferin and isogentisin exerted strong activity against HeLa cells, with IC50 values ranging from 5.7 to 8.8 μg/mL. The results confirm the traditional usage of G. lutea leaves and also suggest their possible utilization as hepatoprotective, hypoglycemic and anti-inflammatory agents.