Flavonoid glycosides of the black locust tree, Robinia pseudoacacia (Leguminosae)

Diosmetin: A dietary flavone as modulator of signaling pathways in cancer progression

Flavonoids, constituting the most extensive category of polyphenols, founds in a variety of plants and comprise over 9000 compounds. Diosmetin, O-methylated flavone (3',5,7-trihydroxy-4'-methoxyflavone) of flavonoid aglycone diosmin have witnessed a significant surge in recent years. Many studies showed that flavonoids induced cytotoxicity in different organ specific cancer types. Thus, current review evaluates the anticancer potential of diosmetin and shed light on its mechanism of action such as cell cycle regulation, apoptosis via both intrinsic and extrinsic pathway, autophagy and tumour progression and metastasis. It also provides comprehensive analysis of different cancer targets and their role in breast, colon, hepatic, gliomas, leukemia, lung, prostate and skin cancer. Combination studies of diosmetin to improve drug sensitivity and reduce toxicity towards normal cells has been also discussed. Besides, in vitro studies, present review also discuss the anticancer potential of diosmetin on xenograft mice model. Different natural sources of diosmetin, limitations, pharmacokinetic analysis and toxicity study also summarized in current review. The emphasis on enhancing solubility and permeability for clinical utility has been thoroughly highlighted with particular attention given to the utilization of nano formulations to overcome existing barriers. At last, in-depth analysis of current challenges and a forward-looking perspective deliberated to address the existing gaps and position it as a promising lead compound for clinical applications in cancer treatment. This discussion is boosted by diosmetin's potential anticancer properties on different cancers, makes valuable candidates in the ongoing quest for effective therapeutic interventions against cancer.

Stabilization of Black Locust Flower Extract via Encapsulation Using Alginate and Alginate-Chitosan Microparticles

Black locust flower extract contains various polyphenols and their glucosides contribute to the potential health benefits. After intake of these bioactive compounds and passage through the gastrointestinal tract, their degradation can occur and lead to a loss of biological activity. To overcome this problem, the bioactive compounds should be protected from environmental conditions. This study aimed to encapsulate the black flower extract in the microparticles based on biodegradable polysaccharides, alginate, and chitosan. In the extract, the total antioxidant content was found to be 3.18 ± 0.01 g gallic acid equivalent per 100 g of dry weight. Also, the presence of lipids (16), phenolics (27), organic acids (4), L-aspartic acid derivative, questinol, gibberellic acid, sterol, and saponins (2) was confirmed using the UHPLC-ESI-MS analysis. In vitro assays showed that the extract has weak anti-α-glucosidase activity and moderate antioxidant and cytotoxic activity against the HeLa cell line. The extrusion method with secondary air flow enabled the preparation of microparticles (about 270 μm) encapsulated with extract. An encapsulation efficiency of over 92% was achieved in the alginate and alginate-chitosan microparticles. The swelling study confirmed a lower permeability of alginate-chitosan microparticles compared with alginate microparticles. For both types of microparticles, the release profile of antioxidants in the simulated gastrointestinal fluids at 37 °C followed the Korsmeyer-Peppas model. A lower diffusion coefficient than 0.5 indicated the simple Fick diffusion of antioxidants. The alginate-chitosan microparticles enabled a more sustained release of antioxidants from extract compared to the alginate microparticles. The obtained results indicated an improvement in the antioxidant activity of bioactive compounds from the extract and their protection from degradation in the simulated gastric conditions via encapsulation in the polymer matrixes. Alginate-chitosan showed slightly slower cumulative antioxidant release from microparticles and better antioxidant activity of the extract compared to the alginate system. According to these results, alginate-chitosan microparticles are more suitable for further application in the encapsulation of black locust flower extract. Also, the proposed polymer matrix as a drug delivery system is safe for human use due to its biodegradability and non-toxicity.

Fermentation of Robinia pseudoacacia flower for improving the antioxidation: optimized conditions, active composition, mechanism, and biotransformation process

Robinia pseudoacacia flower is a natural product with many biological activities, including antioxidation. To further develop its antioxidation, the extract was fermented by Aspergillus niger FFCC 3112 in the medium with carbon to nitrogen ratio of 1.4:1 and initial pH of 4.2 for 3.5 days to form the best antioxidant activity of the fermentation product by strain screening, single factor optimization, and response surface methodology. Further analysis, isolation and activity determination showed that a main chemical component, kaempferol-3-O-α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranosyl-7-O-α-L-rhamnopyranoside, in the extract was completely hydrolyzed to kaempferol-7-O-α-L-rhamnopyranoside and kaempferol with better antioxidant activity through biotransformation, which was the basis for improving the antioxidant activity of fermentation products. Moreover, the mechanism of antioxidant and the contribution of phenolic hydroxyl groups were investigated by density functional theory. The result indicated that the antioxidant capacity of kaempferol-7-O-α-L-rhamnopyranoside and kaempferol increased with the increase of solvent polarity. In high-polarity solvents, they mainly scavenge free radicals through single electron transfer followed by proton transfer.

Invasive Alien Species as a Potential Source of Phytopharmaceuticals: Phenolic Composition and Antimicrobial and Cytotoxic Activity of Robinia pseudoacacia L. Leaf and Flower Extracts

Black locust (Robinia pseudoacacia L.), an invasive tree in Europe, commonly known for its negative impact on biodiversity, is a rich source of phenolic compounds recognized in traditional medicine. Since the metabolite profile depends on the environment and climate, this study aimed to provide the first LC-MS phytochemical screening of the black locust from the Istria region (Croatia). The compounds were extracted from leaves and flowers with 70% ethanol and 80% methanol. Total phenolics (TP) and flavonoids (TF), as well as antioxidant capacity (AC) measured by ABTS (17.49-146.41 mg TE/g DW), DPPH (24.67-118.49 mg TE/g DW), and FRAP (7.38-77.53 mg TE/g DW) assays, were higher in leaf than in flower extracts. Higher TP and total non-flavonoid (TNF) values were displayed in ethanolic than in methanolic extracts. In total, 64 compounds were identified, of which flavonols (20) and hydroxycinnamic acid derivatives (15) were the most represented. Flavanols such as catechin dominated in leaf extracts, followed by flavonols, with kaempferol glucuronyl rhamnosyl hexosides as the main compound, respectively. Flower extracts had the highest share of flavones, followed by ellagitannins, with luteolin dirhamnosyl hexosides and vescalagin, respectively, being predominant. The extracts had good quorum sensing, biofilm formation prevention, and eradicating capacity. The results provided new insights into the phytochemical properties of R. pseudoacacia as the first step toward its potential pharmaceutical use.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Nutritional Attributes and Phenolic Composition of Flower and Bud of Sophora japonica L. and Robinia pseudoacacia L

Sophora japonica L. (SJL) and Robinia pseudoacacia L. (RPL) are widely cultivated in China. However, the utilization of their main by-products are limited due to a lack of comprehensive nutritional attributes. Herein, the proximate composition, mineral elements, fatty acids, amino acids, monosaccharides, and phenolics were analyzed to investigate the nutritional attributes of SJL and RPL. Dietary fiber was the main ingredient in SJL and RPL, followed by protein and lipids. The content of Fe in SJL and RPL was highest, especially in flowers of SJL, reaching about 1179.51 mg/kg. The total unsaturated fatty acids accounted for 89.67% of the bud of SJL. Meanwhile, the essential amino acids contents of the flower and bud of SJL and RPL accounted for 35.95-40.59% of total amino acids. The flower of SJL (373.75 mg/g) exhibited the most abundant monosaccharides. Meanwhile, the total phenolics and flavonoid contents in the buds of SJL and RPL were significantly higher than that of the flower, implying the buds possessed better biological activity. Moreover, the bud of SJL possessed the most abundant phenolics. The results provided a reference for the development of functional food derived from SJL and RPL.

Metabolomics-Based Profiling of Clerodendrum speciosum (Lamiaceae) Leaves Using LC/ESI/MS-MS and In Vivo Evaluation of Its Antioxidant Activity Using Caenorhabditis elegans Model

We investigated the antioxidant activity of the total methanol extract of C. speciosum leaves (CST), the ethyl acetate (CSE), and the remaining aqueous (CSR) fractions in vitro, in vivo using Caenorhabditis elegans model, and in silico. LC-ESI-MS/MS analysis was employed for metabolic profiling of CST. ADME/TOPAKT prediction was performed to determine the potential pharmacokinetic, pharmacodynamic, and toxicity properties of the major identified phytoconstituents. All examined samples showed considerable antioxidant activity where CST, CSE, and CSR displayed EC₅₀ values of 27.1, 16.2, and 21.3 µg/mL, respectively, in 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) assay, whereas they showed 11.44, 16.27, and 12.16 Fe²⁺ equivalents/mg of sample, respectively, in ferric reducing antioxidant power (FRAP) assay. CST, CSE, and CSR displayed total phenolic content of 262, 326, and 289 mg GAE/g sample, respectively. In vivo antioxidant study revealed that CST at 150 μg/mL increased the survival rate of C. elegans by 71.88% compared to untreated group. Regarding intracellular reactive oxygen species (ROS), worms treated with 150 μg/mL of CSE exhibited 60.42% reduction of ROS compared to the untreated group. Quantitation of hsp-16.2/GFP expression in Caenorhabditis elegans showed that worms treated with 150 μg/mL of CSR exerted 40.43% reduction in fluorescence with respect to the untreated group. LC-ESI-MS/MS of CST revealed the presence of sixteen secondary metabolites belonging mainly to polyphenolics with phenyl propanoids constituting the major detected class. The in silico study showed that rosmarinic acid displayed the best fitting within the active sites of Daf-2 protein with considerable safety profile and limited pharmacokinetic and pharmacodynamic that could be slightly enhanced by certain treatment.

Snailase: A Promising Tool for the Enzymatic Hydrolysis of Flavonoid Glycosides From Plant Extracts

Plants typically contain a broad spectrum of flavonoids in varying concentrations. As a rule, several flavonoid classes occur in parallel, and, even for a single flavonoid, divergent glycosylation patterns are frequently observed, many of which are not commercially available. This can be challenging in studies in which the distribution between flavonoid classes, or features that are not affected by glycosylation patterns, are adressed. In addition, hydrolysis simplifies the quantification process by reducing peak interferences and improving the peak intensity due to the accumulation of the respective aglycone. Effective removal of glycose moieties can also be relevant for technological applications of flavonoid aglycones. Herein, we present a fast and reliable method for the enzymatic hydrolysis glycosides from plant extracts using the commercial enzyme mix snailase, which provided the highest aglycone yields across all investigated flavonoids (aurones: leptosidin, maritimetin, sulfuretin; chalcones: butein, lanceoletin, okanin, phloretin; dihydroflavonols: dihydrokaempferol; flavanones: eriodictyol, hesperetin; flavones: acacetin, apigenin, diosmetin, luteolin; flavonols: isorhamnetin, kaempferol, myricetin, quercetin; isoflavones: biochanin A, formononetin, genistein) from methanolic extracts of nine plants (Bidens ferulifolia, Coreopsis grandiflora, Fagus sylvatica, Malus × domestica, Mentha × piperita, Petunia × hybrida, Quercus robur, Robinia pseudoacacia, and Trifolium pratense) in comparison to four other enzymes (cellobiase, cellulase, β-glucosidase, and pectinase), as well as to acidic hydrolysis by hydrochloric acid.

Phytochemical Profile and Microbiological Activity of Some Plants Belonging to the Fabaceae Family

This study aimed to investigate the chemical composition and the activity against Staphylococcus aureus (S. aureus) (ATCC 25923), Streptococcus pyogenes (S. pyogenes) (ATCC 19615), Escherichia coli (E. coli) (ATCC 25922), Pseudomonas aeruginosa (P. aeruginosa) (ATCC 27853), Shigella flexneri (S. flexneri) (ATCC 12022), Salmonella typhimurium (S. typhimurium) (ATCC 14028), Haemophillus influenzae (H. influenza) type B (ATCC 10211) and two fungal strains: Candida albicans (C. albicans) (ATCC 10231) and Candida parapsilopsis (C. parapsilopsis) (ATCC 22019) of the extracts obtained from Melilotus officinalis (MO), Coronilla varia (CV); Ononis spinosa (OS) and Robinia pseudoacacia (RP) (Fabaceae), and to identify the chemical compounds responsible for the antimicrobial effect against the tested strains. The extracts were obtained by conventional hydroalcoholic extraction and analyzed in terms of total polyphenols using the spectrophotometric method and by liquid chromatography (LC). The results have shown that the highest polyphenols content was recorded in the RP sample (16.21 mg gallic acid equivalent GAE/g), followed by the CV (15.06 mg GAE/g), the OS (13.17 mg GAE/g), the lowest value being recorded for the MO sample (11.94 mg GAE/g). The antimicrobial testing of plant extracts was carried out using the microdilution method. The most sensitive strains identified were: E. coli, S. typhimurium, P. aeruginosa and S. pyogenes, while protocatechuic acid, gallic acid, caffeic acid, quercetin, rutin, and kaempferol were identified as the chemical compounds responsible for the antibacterial effect. The analysis of the correlation between the chemical composition and the antimicrobial effect proved a moderate (r > 0.5) positive correlation between rosmarinic acid and S. pyogenes (r = 0.526), rosmarinic acid and S. typhimurium (r = 0.568), quercetin and C. albicans (r = 0.553), quercetin and S. pyogenes (r = 0.605). Therefore, it suggested possible antimicrobial activity generated by these chemical components. The results recommend the Fabaceae plants as promising candidates for further research to develop novel natural antimicrobial drugs.

TRAPPC13 Is a Novel Target of Mesorhizobium amorphae Type III Secretion System Effector NopP

Similar to pathogenic bacteria, rhizobia can inject effector proteins into host cells directly to promote infection via the type III secretion system (T3SS). Nodulation outer protein P (NopP), a specific T3SS effector of rhizobia, plays different roles in the establishment of multiple rhizobia-legume symbiotic systems. Mesorhizobium amorphae CCNWGS0123 (GS0123), which infects Robinia pseudoacacia specifically, secretes several T3SS effectors, including NopP. Here, we demonstrate that NopP is secreted through T3SS-I of GS0123 during the early stages of infection, and its deficiency decreases nodule nitrogenase activity of R. pseudoacacia nodules. A trafficking protein particle complex subunit 13-like protein (TRAPPC13) has been identified as a NopP target protein in R. pseudoacacia roots by screening a yeast two-hybrid library. The physical interaction between NopP and TRAPPC13 is verified by bimolecular fluorescence complementation and coimmunoprecipitation assays. In addition, subcellular localization analysis reveals that both NopP and its target, TRAPPC13, are colocalized on the plasma membrane. Compared with GS0123-inoculated R. pseudoacacia roots, some genes associated with cell wall remodeling and plant innate immunity down-regulated in ΔnopP-inoculated roots at 36 h postinoculation. The results suggest that NopP in M. amorphae CCNWGS0123 acts in multiple processes in R. pseudoacacia during the early stages of infection, and TRAPPC13 could participate in the process as a NopP target.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Fibers Obtained from Invasive Alien Plant Species as a Base Material for Paper Production

Invasive alien plant species (IAPS) are one of the biggest challenges in European ecosystems, displacing local vegetation, destroying agricultural land, and causing billions of dollars of damage to the European economy every year. Many of them are removed daily and mainly burned. In this work, we investigated the possibilities of using plants as feedstock for paper production. Papers made from three invasive alien plants, i.e., Knotweed, Goldenrod, and Black locust, were studied and compared with commercial office paper. The study included testing of: (1) structural properties—basic physical properties, grammage, thickness, density and specific volume, moisture content, and ash content; (2) physical and dynamic mechanical properties—tensile strength, Clark stiffness, viscoelastic properties; (3) colorimetric properties of prints; (4) effect of UV light on ageing; and (5) study of cellulose fiber structure and morphology by microscopy. The results suggested that the paper produced can be used as commercial office paper, considering that the paper is slightly dyed. Such papers can also be used for special purposes that present a natural style and connection to nature. The papers produced can also be used for printing documents that are meant to be kept.

The combined effects of elevated atmospheric CO2 and cadmium exposure on flavonoids in the leaves of Robinia pseudoacacia L. seedlings

Flavonoids participate in several plant processes such as growth and physiological protection in adverse environments. In this study, we investigated the combined effects of eCO₂ and cadmium (Cd)-contaminated soils on the total flavonoid and monomer contents in the leaves of Robinia pseudoacacia L. seedlings. Elevated CO₂, Cd, and eCO₂+ Cd increased the total flavonoids in the leaves relative to the control, and eCO₂ mostly increased (p < 0.05) the total flavonoid content under Cd exposure. Elevated CO₂ increased (p < 0.05) robinin, rutin, and acacetin contents in the leaves of 45-day seedlings and decreased (p < 0.05) the content of robinin and acacetin at 90 and 135 d under Cd exposure except for robinin at day 45 under Cd1 and acacetin on day 135 under Cd1. Quercetin content decreased (p < 0.05) under the combined conditions relative to Cd alone. Kaempferol in the leaves was only detected under eCO₂ on day 135. The responses of total chlorophyll, total soluble sugars, starch, C, N, S, and the C/N ratio in the leaves to eCO₂ significantly affected the synthesis of total flavonoids and monomers under Cd exposure. Overall, rutin was more sensitive to eCO₂+ Cd than the other flavonoids. Cadmium, CO_2, and time had significant interactive effects on the synthesis of flavonoids in the leaves of R. pseudoacacia L. seedlings. Elevated CO₂ may improve the protection and defense system of seedlings grown in Cd-contaminated soils by promoting the synthesis of total flavonoids, although robinin, rutin, quercetin, and acacetin yields may reduce with time. Additionally, increased Cd in the leaves suggested that eCO₂ could improve the phytoremediation of Cd-contaminated soils.

A new flavonoid, a new phenylethanoid glycoside and related compounds isolated from the inflorescences of Plantago lanceolata L

For the first time inflorescences of a plant species from the genus Plantago (Pantaginaceae)-Plantago lanceolata L. (Ribwort Plantain), a known medicinal plant, were subjected to studies of phenolic compounds, which resulted in an isolation of two new compounds: a flavonoid-isorhamnetin 3-O-α-L-⁴C₁-arabinopyranosyl-(1→2)-β-D-⁴C₁-glucopyranoside) (1) and a phenylethanoid glycoside-2-(3,4-dihydroxyphenyl)ethyl O-α-L-arabinofuranosyl-(1→2)-[α-L-¹C₄-rhamnopyranosyl-(1→3)][E-caffeoyl-1→4]-β-D-⁴C₁-glucopyranoside (14), along with fourteen known compounds-eight flavonoids (2-9) and six phenylethanoid glycosides (10-13, 15-16). The chemical structures were established by 1 D and 2 D NMR and HRESIMS spectral methods. The known phenylethanoids were the same as reported for leaves or aerial parts of P. lanceolata or other Plantago species. The flavonoids appeared to be only flavonols, mainly isorhamnetin 3-O- and 3,4'-O- glycosides, and thus completely different from flavones, mainly luteolin and apigenin glucuronides, previously reported in the leaves. The possible medicinal and chemotaxonomic relevance of the phenolics found in P. lanceolata inflorescences were taken into consideration.

Effect of Robinia pseudoacacia Leaf Extract on Interleukin-1β-mediated Tumor Angiogenesis

BACKGROUND/AIM

Interleukin (IL)-1β is a pro-inflammatory cytokine that has recently been established as a stimulator of angiogenesis via regulation of proangiogenic factor expression in the tumor microenvironment. This study aimed to demonstrate the inhibitory effects of Robinia pseudoacacia leaf extract (RP) on IL-1β-mediated tumor angiogenesis.

MATERIALS AND METHODS

Secreted embryonic alkaline phosphatase (SEAP) reporter gene assay, ex vivo and in vitro tube formation assay, western blot, and quantitative PCR were used to analyze the inhibitory effect of RP on IL-1β-mediated angiogenesis.

RESULTS

RP inhibited secretion of SEAP, blocked IL-1β signaling, and inhibited IL-1β-mediated angiogenesis in ex vivo and in vitro assays. RP inhibited nuclear translocation of NF-ĸB by suppressing phosphorylation of IL-1β signaling protein kinases and inhibited mRNA expression of IL-1β-induced pro-angiogenic factors including VEGFA, FGF2, ICAM1, CXCL8, and IL6.

CONCLUSION

RP suppressed IL-1β-mediated angiogenesis and, thus, could be a promising agent in anticancer therapy.

Type III secretion systems impact Mesorhizobium amorphae CCNWGS0123 compatibility with Robinia pseudoacacia

Rhizobia and legume plants are famous mutualistic symbiosis partners who provide nitrogen nutrition to the natural environment. Rhizobial type III secretion systems (T3SSs) deliver effectors that manipulate the metabolism of eukaryotic host cells. Mesorhizobium amorphae CCNWGS0123 (GS0123) contains two T3SS gene clusters, T3SS-I and T3SS-II. T3SS-I contains all the basal components for an integrated T3SS, and the expression of T3SS-I genes is up-regulated in the presence of flavonoids. In contrast, T3SS-II lacks the primary extracellular elements of T3SSs, and the expression of T3SS-II genes is down-regulated in the presence of flavonoids. Inoculation tests on Robinia pseudoacacia displayed considerable differences in gene expression patterns and levels among roots inoculated with GS0123 and T3SS-deficient mutant (GS0123ΔrhcN1 (GS0123ΔT1), GS0123ΔrhcN2 (GS0123ΔT2) and GS0123ΔrhcN1ΔrhcN2 (GS0123ΔS)). Compared with the GS0123-inoculated plants, GS0123ΔT1-inoculated roots formed very few infection threads and effective nodules, while GS0123ΔT2-inoculated roots formed a little fewer infection threads and effective nodules with increased numbers of bacteroids enclosed in one symbiosome. Moreover, almost no infection threads or effective nodules were observed in GS0123ΔS-inoculated roots. In addition to evaluations of plant immunity signals, we observed that the coexistence of T3SS-I and T3SS-II promoted infection by suppressing host defense response in the reactive oxygen species defense response pathway. Future studies should focus on identifying rhizobial T3SS effectors and their host target proteins.

Evaluation of antiviral effect and toxicity of total flavonoids extracted from Robinia pseudoacacia cv. idaho

In this study, we aimed to evaluate the antiviral effect of total flavonoids extracted from Robinia pseudoacacia cv. idaho (RPTF) in vivo and its toxicity on rats with oral gavage. RPTF was prepared by percolation with 70% ethanol for 24 h and its antiviral effect on different kinds of viruses was evaluated in vitro by MTT staining. The long-term toxicity of RPTF on rats was evaluated through the detection of general behavior, body weight, food intake and related organ tissue sections of experimental animals. We found that RPTF produced significantly inhibitory effects on HSV-1 and EV-71 viruses with the therapeutic index TI values 113.8 and 46.2, respectively. Moreover, toxicity evaluation in vivo showed no significantly adverse effects in rats, indicating that RPTF was safe in use. In conclusion, we demonstrated that RPTF, natural compounds in the Chinese traditional medicine, could act as promising and effective antiviral therapeutics with relative safety in use.

Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Black Locust (Robiniae Pseudoacaciae) Flowers and Comparison with Conventional Methods

The aim of this study was to optimize the ultrasound-assisted extraction of phenolic compounds from black locust (Robiniae pseudoacaciae) flowers using central composite design. The ethanol concentration (33-67%), extraction temperature (33-67 °C), and extraction time (17-33 min) were analyzed as the factors that impact the total phenolic content. The liquid-to-solid ratio of 10 cm3 g-1 was the same during extractions. The optimal conditions were found to be 59 °C, 60% (v/v) ethanol, and extraction time of 30 min. The total phenolic content (TPC = 3.12 gGAE 100 g-1 dry plant material) and antioxidant activity (IC50 = 120.5 µg cm-3) of the extract obtained by ultrasound-assisted extraction were compared with those obtained by maceration (TPC = 2.54 gGAE 100 g-1 dry plant material, IC50 = 150.6 µg cm-3) and Soxhlet extraction (TPC = 3.22 gGAE 100 g-1 dry plant material, IC50 = 204.2 µg cm-3). The ultrasound-assisted extraction gave higher total phenolic content and better antioxidant activity for shorter extraction time so that it represents the technique of choice for the extraction of phenolic compounds. The obtained extract, as the source of antioxidants, can be applied in the pharmaceutical and food industries.

The Phytochemistry of Cherokee Aromatic Medicinal Plants

Background: Native Americans have had a rich ethnobotanical heritage for treating diseases, ailments, and injuries. Cherokee traditional medicine has provided numerous aromatic and medicinal plants that not only were used by the Cherokee people, but were also adopted for use by European settlers in North America. Methods: The aim of this review was to examine the Cherokee ethnobotanical literature and the published phytochemical investigations on Cherokee medicinal plants and to correlate phytochemical constituents with traditional uses and biological activities. Results: Several Cherokee medicinal plants are still in use today as herbal medicines, including, for example, yarrow (Achillea millefolium), black cohosh (Cimicifuga racemosa), American ginseng (Panax quinquefolius), and blue skullcap (Scutellaria lateriflora). This review presents a summary of the traditional uses, phytochemical constituents, and biological activities of Cherokee aromatic and medicinal plants. Conclusions: The list is not complete, however, as there is still much work needed in phytochemical investigation and pharmacological evaluation of many traditional herbal medicines.

Isolation and Identification of the Five Novel Flavonoids from Genipa americana Leaves

Genipa americana is a medicinal plant popularly known as "jenipapo", which occurs in Brazil and belongs to the Rubiaceae family. It is a species widely distributed in the tropical Central and South America, especially in the Cerrado biome. Their leaves and fruits are used as food and popularly in folk medicine to treat anemias, as an antidiarrheal, and anti-syphilitic. Iridoids are the main secondary metabolites described from G. americana, but few studies have been conducted with their leaves. In this study, the aim was to chemical approach for identify the main compounds present at the extract of G. americana leaves. The powdered leaves were extracted by maceration with EtOH: water (70:30, v/v), following liquid-liquid partition with petroleum ether, chloroform, ethyl acetate and n-butanol. A total of 13 compounds were identified. In addition three flavonoids were isolated from the ethyl acetate fraction: quercetin-3-O-robinoside (GAF 1), kaempferol-3-O-robinoside (GAF 2) and isorhamnetin-3-O-robinoside (GAF 3) and, from n-butanol fraction more two flavonoids were isolated, kaempferol-3-O-robinoside-7-O-rhamnoside (robinin) (GAF 4) and isorhamnetin-3-O-robinoside-7-rhamnoside (GAF 5). Chemical structures of these five flavonoids were elucidated using spectroscopic methods (MS, ¹H and ¹³C-NMR 1D and 2D). These flavonoids glycosides were described for the first time in G. americana.

From Robinia pseudoacacia L. nectar to Acacia monofloral honey: biochemical changes and variation of biological properties

BACKGROUND

Robinia pseudoacacia L. nectar and its derivative monofloral honey were systematically compared in this study, to understand how much the starting solution reflected the final product, after re-elaboration by Apis mellifera ligustica Spinola.

RESULTS

Subjected to dehydration in the hive, nectar changed in its water and sugar content when transformed into honey, as physicochemical and gas chromatographic-mass spectrometric analyses revealed. Spectrophotometric measurements and characterization by high-performance liquid chromatography-diode array detection of 18 plant molecules demonstrated honey to be richer than nectar in secondary metabolites. For the first time, the hypothesis of the existence of a nectar redox cycle in R. pseudoacacia was reported, as previously described for Nicotiana sp., based on 1D-protein profiles, western blot analysis and detection of H₂ O₂ and ascorbate. The bioactivity of both matrices was also investigated. Antiradical in vitro tests showed that Acacia honey was more antioxidant than nectar, which was even able to induce oxidative stress directly in a eukaryotic cell system. Antimicrobial assays demonstrated that nectar was bacteriostatic, due to H₂ O₂ activity, whereas honey was even bactericidal.

CONCLUSION

All these data support the ecological role of nectar and honey in nature: protection of the gynoecium from pathogens and preservation from degradative processes, respectively. © 2018 Society of Chemical Industry.

Bactericidal effect of extracts and metabolites of Robinia pseudoacacia L. on Streptococcus mutans and Porphyromonas gingivalis causing dental plaque and periodontal inflammatory diseases

The mouth cavity hosts many types of anaerobic bacteria, including Streptococcusmutans and Porphyromonas gingivalis, which cause periodontal inflammatory diseases and dental caries. The present study was conducted to evaluate the antibacterial potential of extracts of Robinia pseudoacacia and its different fractions, as well as some of its natural compounds against oral pathogens and a nonpathogenic reference bacteria, Escherichia coli. The antibacterial activity of the crude extract and the solvent fractions (hexane, chloroform, ethyl acetate and butanol) of R. pseudoacacia were evaluated against S.mutans, P. gingivalis and E. coliDH5α by standard micro-assay procedure using conventional sterile polystyrene microplates. The results showed that the crude extract was more active against P. gingivalis (100% growth inhibition) than against S. mutans (73% growth inhibition) at 1.8 mg/mL. The chloroform and hexane fractions were active against P. gingivalis, with 91 and 97% growth inhibition, respectively, at 0.2 mg/mL. None of seven natural compounds found in R. pseudoacacia exerted an antibacterial effect on P. gingivalis; however, fisetin and myricetin at 8 µg/mL inhibited the growth of S. mutans by 81% and 86%, respectively. The crude extract of R. pseudoacacia possesses bioactive compounds that could completely control the growth of P. gingivalis. The antibiotic activities of the hexane and chloroform fractions suggest that the active compounds are hydrophobic in nature. The results indicate the effectiveness of the plant in clinical applications for the treatment of dental plaque and periodontal inflammatory diseases and its potential use as disinfectant for various surgical and orthodontic appliances.

Identification and quantification of the sedative and anticonvulsant flavone glycoside from Chrysanthemum boreale

The flowers or leaves of Chrysanthemum boreale (Compositae) have been traditionally used as herb tea to reduce anxiety, insomnia, and stress. Sedative and anticonvulsant activities were evaluated in mice using pentobarbital-induced sleeping assay and pentylenetetrazole (PTZ)-induced convulsion assay. The flower extract exhibited more potent activities than the extracts of the leaves and stems, and chromatographic isolation yielded the five compounds acacetin, linarin, acacetin 7-O-β-D-glucopyranosyl-(1 → 2)[α-L-rhamnopyranosyl-(1 → 6)]-β-D-glucopyranoside, chlorogenic acid, and 3,5-di-O-caffeoylquinic acid. These compounds were simultaneously analyzed by HPLC, and the method was validated. The contents of linarin, which were shown to be most abundant in C. boreale, were observed in the order of leaf (11.93 mg/g) > flower (8.50 mg/g) > stem (5.60 mg/g). Linarin and its aglycone, acacetin, exhibited sedative and anticonvulsant activities in the present in vivo assays. It can be considered that linarin is one of the active compounds effective against anxiety, insomnia, and stress, with acacetin as its active moiety.

Geranyl Flavonoids from Robinia pseudoacacia

A new geranyl flavonol, robipseudin A (1), and a known geranyl flavone, kuwanon S (2), were isolated from the leaves of Robinia pseudoacacia. The structure of the new compound was determined by spectroscopic methods. Compounds 1 and 2 showed moderate antioxidant activities in the DPPH radical scavenging assay.

Flavone tetraglycosides and benzyl alcohol glycosides from the Mongolian medicinal plant Dracocephalum ruyschiana

From an extract of the aerial parts of Dracocephalum ruyschiana, five new flavone tetraglycosides, five new benzyl alcohol glycosides, and 19 known compounds were isolated. The tetraglycosides contain a 7-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)]-β-d-glucopyranosyl moiety. The benzyl alcohol glycosides had acyl groups on their glycosyl or aglycone moieties. The compounds were tested for antioxidant activity using DPPH. Although the new compounds were not active, phenylpropanoylquinic acid derivatives were revealed as radical scavengers in D. ruyschiana.

Inhibitory activity of coumarins from Artemisia capillaris against advanced glycation endproduct formation

Since glycation can lead to the onset of diabetic complications due to chronic hyperglycemia, several indigenous Artemisia species were evaluated as potential inhibitors of advanced glycation endproducts (AGE). Among them, the Artemisia capillaris plant demonstrated the highest AGE inhibitory activity. Repeated column chromatography was performed to isolate a new acylated flavonoid glycoside, acacetin-7-O-(6″-O-acetyl)-β-D-glucopyranosyl-(1→2)[α-L-rhamnopyranosyl]-(1→6)-β-D-glucopyranoside, along with 11 known flavonoids (acacetin-7-O-β-D-glucopyranosyl-(1→2)[α-L-rhamnopyranosyl]-(1→6)-β-D-glucopyranoside, linarin, quercetin, hyperoside, isorhamnetin, isorhamnetin 3-galactoside, isorhamnetin 3-glucoside, isorhamnetin 3-arabinoside, isorhamnetin 3-robinobioside, arcapillin, and cirsilineol), six coumarins (umbelliferone, esculetin, scopoletin, scopolin, isoscopolin, and scoparone), and two phenolic derivatives (4,5-di-O-caffeoylquinic acid and chlorogenic acid). In determining the structure-activity relationship (SAR), it was found that the presence and position of hydroxyl group of test coumarins (coumarin, esculin, isoscopoletin, daphnetin, 4-methylcoumarin, and six isolated coumarins) may play a crucial role in AGE inhibition. A free hydroxyl group at C-7 and a glucosyl group instead of a methoxyl group at C-6 are two important parameters for the inhibitory potential of coumarins on AGE formation. A. capillaris and five key AGE inhibitors, including 4,5-di-Ocaffeoylquinic acid, umbelliferone, esculetin, esculin, and scopoletin, were identified as potential candidates for use as therapeutic or preventive agents for diabetic complications and oxidative stress-related diseases. We understand this to be the first detailed study on the SAR of coumarins in AGE inhibition.

Potent antiviral flavone glycosides from Ficus benjamina leaves

Crude ethanol extracts from Ficus benjamina leaves strongly inhibit Herpes Simplex Virus 1 and 2 (HSV-1/2) as well as Varicella Zoster Virus (VZV) cell infection in vitro. Bioassay-guided fractionation of the crude extract demonstrated that the most efficient inhibition of HSV-1 and HSV-2 was obtained with the flavonoid fraction. The present study was aimed to further isolate, purify and identify substances with potent antiviral activity from the flavonoid fraction of F. benjamina extracts. Flavonoids were collected from the leaf ethanol extracts through repeated purification procedure and HPLC analysis. The antiviral activity of each substance was then evaluated in cell culture. Three known flavone glycosides, (1) quercetin 3-O-rutinoside, (2) kaempferol 3-O-rutinoside and (3) kaempferol 3-O-robinobioside, showing highest antiviral efficiency were selected and their structure was determined by spectroscopic analyses including NMR and mass spectrometry (MS). These three flavones were highly effective against HSV-1 reaching a selectivity index (SI) of 266, 100 and 666 for compound 1, 2 and 3, respectively, while the SI of their aglycons, quercetin and kaempferol amounted only in 7.1 and 3.2, respectively. Kaempferol 3-O-robinobioside showed similar SI to that of acyclovir (ACV), the standard anti-HSV drug. Although highly effective against HSV-1 and HSV-2, these flavone glycosides did not show any significant activity against VZV.

Identification of common glycosyl groups of flavonoid O-glycosides by serial mass spectrometry of sodiated species

Flavonoid O-glycosides are a ubiquitous and important group of plant natural products in which a wide variety of sugars are O-linked to an aglycone. Determining the identity of the sugars, and the manner in which they are linked, by mass spectrometry alone is challenging. To improve the identification of common O-linked di- and trisaccharides when analysing mixtures of flavonoid O-glycosides by liquid chromatography/mass spectrometry (LC/MS), the fragmentation of electrosprayed sodium adducts in an ion trap mass spectrometer was investigated. The sodium adducts [M + Na](+) of kaempferol 3-O-glycosides generated sodiated glycosyl groups by the neutral loss of kaempferol. The product ion spectra of these sodiated glycosyl groups differed between four isomeric kaempferol 3-O-rhamnosylhexosides and four isomeric kaempferol 3-O-glucosylhexosides in which the primary hexose was either glucose or galactose and bore the terminal glucose or rhamnose at either C-2 or C-6. Fragmentation of sodiated glycosyl groups from linear O-triglucosides and branched O-glucosyl-(1 → 2)-[rhamnosyl-(1 → 6)]-hexosides produced sodiated disaccharide residues, and the product ion spectra of these ions assisted the identification of the complete sugar. The product ion spectra of the sodiated glycosyl groups were consistent among flavonoid O-glycosides differing in the position at which the sugar was O-linked to the aglycone, and the nature of the aglycone. The abundance of sodiated species was enhanced by application of a pre-trap collision voltage, without the need to dope with salt, allowing automated LC/MS methods to be used to identify the glycosyl groups of common flavonoid O-glycosides, such as rutinosides, robinobiosides, neohesperidosides, gentiobiosides and sophorosides.