Antiradical activity of Paulownia tomentosa (Scrophulariaceae) extracts

Perspectives on antimicrobial properties of Paulownia tomentosa Steud. fruit products in the control of Staphylococcus aureus infections

ETHNOPHARMACOLOGICAL RELEVANCE

Paulownia tomentosa Steud. (P. tomentosa) is a medium-sized tree traditionally used in Chinese folk medicine for the treatment of infectious diseases. It is a rich source of prenylated phenolic compounds that have been extensively studied for their promising biological activities.

AIM OF THE STUDY

Due to the increasing development of antibiotic resistance, our study investigated plant-derived natural products from the fruits of P. tomentosa that could control Staphylococcus aureus infections with novel targets/modes of action and reduce antimicrobial resistance.

MATERIALS AND METHODS

The ethanolic extract was fractionated and detected by liquid chromatography. The antistaphylococcal effects of the plant formulations were studied in detail in vitro by various biological methods, including microdilution methods for minimum inhibitory concentration (MIC), the checkerboard titration technique for synergy assay, fluorescence measurements for membrane disruption experiments, autoinducer-2-mediated bioassay for quorum sensing inhibition, and counting of colony-forming units for relative adhesion. Morphology was examined by transmission electron microscopy.

RESULTS

Total ethanolic extract and chloroform fraction showed MICs of 128 and 32 μg/mL, respectively. Diplacol, diplacone, and 3'-O-methyl-5'-hydroxydiplacone inhibited S. aureus growth in the range of 8-16 μg/mL. Synergistic potential was shown in combination with mupirocin and fusidic acid. The ethanolic extract and the chloroform fraction destroyed the cell membranes by 91.61% and 79.46%, respectively, while the pure compounds were less active. The ethanolic extract and the pure compounds reduced the number of adhered cells to 47.33-10.26% compared to the untreated control. All tested plant formulations, except diplacone, inhibited quorum sensing of S. aureus. Transmission electron microscopy showed deformation of S. aureus cells.

CONCLUSIONS

The products from the fruit of P. tomentosa showed antimicrobial properties against S. aureus alone and in combination with antibiotics. By affecting intracellular targets, geranylated flavonoids proposed novel approaches in the control of staphylococcal infections.

A carotenoid cleavage dioxygenase 4 from Paulownia tomentosa determines visual and aroma signals in flowers

Paulownia tomentosa is an economically important fast-growing tree, and its flowers and fruits are a rich source of biologically active secondary metabolites. In addition, the flowers of P. tomentosa are distinguished by a strong aroma and are also excellent nectariferous plants. The flowers are pale lilac and characterized by the presence of yellow nectar guides, whose color changes during the development of the flower, representing reliable signals to pollinators while enhancing reproductive success. The chemical analyses of the nectar guides revealed the presence of carotenoids as the pigments responsible for the observed coloration, with β-carotene levels determining the color changes observed after anthesis, with a reduction at anthesis and further increase and accumulation in post anthesis. To understand how β-carotene accumulation was controlled in the nectar guides, the expression of genes related to carotenoid biosynthesis and metabolism was analyzed. Carotenogenic gene expression was not associated with the observed changes in β-carotene during flower development. However, the expression of a gene encoding a carotenoid cleavage dioxygenase, CCD4-4, was co-related with the levels of β-carotene in the nectar guides. In addition, CCD4-4 cleavage β-carotene at C9-C10 and C9'-C10' positions, resulting in the generation of β-ionone, which was detected in flowers at anthesis. The obtained results indicated a developmental stage specific regulation of apocarotenoid formation through β-carotene cleavage, resulting in color changes and volatile production as key traits for plant-pollinator interactions. DATA AVAILABILITY: Data will be made available on request.

A potential host and virus targeting tool against COVID-19: Chemical characterization, antiviral, cytoprotective, antioxidant, respiratory smooth muscle relaxant effects of Paulownia tomentosa Steud

COronaVIrus Disease 2019 (COVID-19) is a newly emerging infectious disease that spread across the world, caused by the novel coronavirus Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2). Despite the advancements in science that led to the creation of the vaccine, there is still an urgent need for new antiviral drugs effective against SARS-CoV-2. This study aimed to investigate the antiviral effect of Paulownia tomentosa Steud extract against SARS-CoV-2 and to evaluate its antioxidant properties, including respiratory smooth muscle relaxant effects. Our results showed that P. tomentosa extract can inhibit viral replication by directly interacting with both the 3-chymotrypsin-like protease and spike protein. In addition, the phyto complex does not reduce lung epithelial cell viability and exerts a protective action in those cells damaged by tert-butyl hydroperoxide , a toxic agent able to alter cells' functions via increased oxidative stress. These data suggest the potential role of P. tomentosa extract in COVID-19 treatment, since this extract is able to act both as an antiviral and a cytoprotective agent in vitro.

Paulownia Organs as Interesting New Sources of Bioactive Compounds

Paulownia spp. is a genus of trees in the Paulowniaceae family. It is native to southeastern Asia (especially China), where it has been cultivated for decorative, cultural, and medicinal purposes for over 2000 years. Depending on taxonomic classification, there are 6 to 17 species of Paulownia; P. tomentosa, P. elongata, P. fortunei, and P. catalpifolia are considered the most popular. Nowadays, Paulownia trees are planted in Asia, Europe, North America, and Australia for commercial, medical, and decorative purposes. Lately, growing interest in Paulownia has led to the development of various hybrids, the best-known being Clone in vitro 112, Shan Tong, Sundsu 11, and Cotevisa 2. Paulownia Clone in vitro 112 is an artificially created hybrid of two species of Paulownia: P. elongata and P. fortunei. The present review of selected papers from electronic databases including PubMed, ScienceDirect, and SCOPUS before 15 November 2022 describes the phytochemical characteristics, biological properties, and economic significance of various organs from different Paulownia species and hybrids, including P. tomentosa, P. elongata, P. fortunei, and Paulownia Clone in vitro 112. Many compounds from Paulownia demonstrate various biological activities and are promising candidates for natural preparations; for example, the leaves of Clone in vitro 112 have anti-radical and anticoagulant potential. However, further in vivo studies are needed to clarify the exact mechanism of action of the active substances and their long-term effects.

Antiproliferative and cytotoxic activities of C-Geranylated flavonoids from Paulownia tomentosa Steud. Fruit

Prenylated or geranylated flavonoids have been studied for their promising antiproliferative and cytotoxic activities. Twelve natural geranylated flavonoids (1-12) were isolated from the fruit of Paulownia tomentosa Steud. Their structures were elucidated using UV and IR spectroscopy, mass spectrometry, and 1D and 2D NMR spectroscopy. The absolute configurations were determined using NMR and circular dichroism. Seven of the compounds were characterized as new geranylated derivatives isolated from a natural source for the first time, namely 3'-O-methyl-5'-hydroxyisodiplacone (3), paulodiplacone A (5), tomentone II (6), tomentone B (7), tomentodiplacone P (8), paulodiplacone B (9), and tomentoflavone A (12). After 24 h of incubation at concentrations in the range 1-30 μM, the isolated compounds were tested for their antiproliferative and cytotoxic potentials against the human monocytic leukaemia cell line THP-1, using WST-1 and LDH assays, respectively. Almost all of the test compounds induced a concentration-dependent reduction in the metabolic activity of THP-1 cells and a concentration-dependent reduction in the cell viability. Diplacone (1) was the most potent antiproliferative and cytotoxic agent (IC₅₀ 9.31 ± 0.72 μM, LC₅₀ 18.01 ± 1.19 µM). 3'-O-Methyl-5'-hydroxydiplacone (2) showed relatively strong antiproliferative effect (IC₅₀ 12.61 ± 0.90 μM) and weaker cytotoxic activity (LC₅₀ > 30 μM), indicating that it may serve as a potential lead compound for further testing. The structure-activity relationship for the 12 isolated compounds is discussed.

Establishment of extraction design space for ursolic acid from Paulowniae Flos based on the concept of quality by design

INTRODUCTION

The application of quality by design (QbD) concept needs to be strengthened in the field of traditional Chinese medicine research. The extraction process has an important influence on the effectiveness of the drug, and the combination of QbD and the extraction process of the active ingredient helps to improve the effectiveness of the drug.

OBJECTIVE

To establish the extraction design space for ursolic acid (UA) from Paulowniae Flos based on the concept of QbD.

METHODS

The extraction yield of the target component UA was taken as critical quality attributes (CQAs), extraction time, extraction temperature, ethanol concentration and liquid-solid ratio, as critical process parameters (CPPs). Box-Behnken design (BBD) was applied to optimise the design space and the chromatographic conditions were performed on a Shimadzu C18 reversed-phase column with 0.1% (v/v) acetic acid aqueous water-acetonitrile (7:13, v/v) as the mobile phase at a 1 mL/min flow rate, using UA standard as a control and detection at 210 nm.

RESULTS

The single factor investigation and BBD experiment were used to construct the design space, while verification experiments and methodological validation were used to demonstrate that the space was robust and analytical methods were appropriate. The operating space of ethanol concentration 93-98%, liquid-solid ratio 28-37 mL/g and extraction temperature 70-78.3°C was recommended.

CONCLUSION

The proposed methodology can help to promote the quality control of the Chinese medicine extraction process and facilitate the production operation of the enterprise easier.

Phytochemical characteristics of Paulownia trees wastes and its use as unconventional feedstuff in animal feed

Due to the continuous increase in animal feed prices, and the presence of competition between humans and animals on food materials, it is imperative to identify other non-food plant resources to assist the animal feed industry and improve livestock productivity. Plant wastes may cause air, soil, and water pollution. However, if judiciously managed, they would be important resources. Plant wastes are used as feedstuffs and fertilizers. However, their use as animal feed is more useful than fertilizers. Because of the high content of fiber and non-protein N, these wastes are more valuable for feeding ruminants than poultry. The use of the plant wastes as feedstuffs could improve the environmental quality and profits for feed producers. Paulownias are fast-growing trees initially cultivated for wood production. However, due to their good nutritive value, their leaves have been used for ruminants, non-ruminants animals and poultry feeding. Furthermore, they are well-known for its medicinal and antibacterial properties. However, little is still known about its characteristics. This review aimed at providing detailed information about the nature, nutritional value, phytochemicals, and uses of Paulownia as a promising feedstuff in the fields of ruminants, non-ruminants, and poultry nutrition.

Paulownia C-geranylated flavonoids: their structural variety, biological activity and application prospects

Paulownia species, especially their flowers and fruits, are traditionally used in Chinese herbal medicines for the treatment of infectious diseases. C-geranylated flavonoids were found to be the major special metabolites in Paulownia flowers and fruits, and 76 C-geranylated flavonoids had been isolated and characterized thus far. Structural variations in Paulownia C-geranylated flavonoids are mainly due to the complicated structural modifications in their geranyl substituents. These natural compounds have attracted much attention because of their various biological activities, including antioxidation, anti-inflammation, cytotoxic activity and various enzymatic inhibitions, etc. Among them, diplacone, a major Paulownia component, was considered to have promise for applications in medicine. This paper summarizes the information from current publications on Paulownia C-geranylated flavonoids, with a focus on their structural variety, key spectroscopic characteristics, biological activity with structure-activity relationships and application prospects. We hope that this paper will stimulate further investigations of Paulownia species and this kind of natural product.

High temperature treatment allows the detection of episesamin in paulownia wood extractives

The composition and the relative variation of secondary metabolites of Paulownia tomentosa S. wood under thermal effect is a little explored area. Wood material was previously thermo-treated at 210 °C for 3 hours using a press vacuum technology. Extractives of untreated and thermo-treated wood material achieved with Soxhlet extraction techniques were obtained. Then the extracts were chromatographed by using thin layer chromatography. Component groups in extracts were determined by gas chromatography in combination with mass spectrometry. In terms of wood change the thermo-treatment of wood induces a darkening of wood color surface (ΔL* = 28.3), an increase of mass loss (3.5%) and an increase of the amount of extractives and lignin content as well as an increase of the chloroform soluble fraction. This work mainly describes the chemical exploration of the extract from paulownia wood, leading to the isolation and identification of episesamin.

Mechanisms on formation of hierarchically porous carbon and its adsorption behaviors

Using simple one-step carbonization-activation, the residues of paulownia flowers are employed as a precursor to prepare hierarchically porous activated carbon. After investigating the optimum conditions, the obtained paulownia flowers based activated carbon (PFAC) is characterized by Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, Brunauer-Emmett-Teller specific surface area analysis (S(BET)), thermo gravimetric analysis, and X-ray photoelectron spectroscopy. The PFAC owns a high specific surface area of 1,053 m(2)/g as well as a hierarchically porous structure with a combination of micro-, meso- and macropores. The pore-forming mechanism is discussed according to results of characterization. Using methylene blue as model dye, the adsorption behaviors of PFAC were investigated. We found that the dye could be rapidly adsorbed by hierarchically porous PFAC, and the adsorption capacity of PFAC reached 300 mg/g.

C-Geranylated Flavanones from Paulownia tomentosa Fruits as Potential Anti-inflammatory Compounds Acting via Inhibition of TNF-α Production

Eleven new C-geranylated flavonoids, tomentodiplacones L, M, and N (1, 2, 10), tomentodiplacol B (3), 3',4'-O-dimethyl-5'-hydroxydiplacone (4), mimulones F, G, and H (5, 6, 7), paulowniones A (8) and B (9), tomentone (11), and 3',4',5'-trimethoxyflavanone (12), together with 11 known flavonoids (13-23), were isolated from fruits of Paulownia tomentosa. The structures of the compounds isolated were determined by spectroscopic data interpretation. The ability of compounds 1-23, together with the nonprenylated flavanones eriodictyol (24) and naringenin (25), to reduce the production of the pro-inflammatory cytokine TNF-α in THP-1 cells after bacterial lipopolysaccharide stimulation was evaluated using an in vitro screening test. The preliminary structure-activity relationships of these derivatives were also studied, and the correlation of their TNF-α inhibitory activity with their lipophilicity was investigated. The mechanism of action of compounds with significant antiphlogistic potential (4, 7, 10, 14, 22) was investigated. These compounds reduced both the secretion of TNF-α and the level of its corresponding mRNA. Compounds 4, 7, 10, 14, and 22 inhibited the nuclear translocation of NF-κB, which controls the expression of TNF-α, by blocking the degradation of IκB.

Mimulone-induced autophagy through p53-mediated AMPK/mTOR pathway increases caspase-mediated apoptotic cell death in A549 human lung cancer cells

Anticancer properties and mechanisms of mimulone (MML), C-geranylflavonoid isolated from the Paulownia tomentosa fruits, were firstly elucidated in this study. MML prevented cell proliferation in a dose- and time-dependent way and triggered apoptosis through the extrinsic pathway in A549 human lung adenocarcinoma cells. Furthermore, MML-treated cells displayed autophagic features, such as the formation of autophagic vacuoles, a primary morphological feature of autophagy, and the accumulation of microtubule-associated protein 1 light chain 3 (LC3) puncta, another typical maker of autophagy, as determined by FITC-conjugated immunostaining and monodansylcadaverine (MDC) staining, respectively. The expression levels of LC3-I and LC3-II, specific markers of autophagy, were also augmented by MML treatment. Autophagy inhibition by 3-methyladenine (3-MA), pharmacological autophagy inhibitor, and shRNA knockdown of Beclin-1 reduced apoptotic cell death induced by MML. Autophagic flux was not significantly affected by MML treatment and lysosomal inhibitor, chloroquine (CQ) suppressed MML-induced autophagy and apoptosis. MML-induced autophagy was promoted by decreases in p53 and p-mTOR levels and increase of p-AMPK. Moreover, inhibition of p53 transactivation by pifithrin-α (PFT-α) and knockdown of p53 enhanced induction of autophagy and finally promoted apoptotic cell death. Overall, the results demonstrate that autophagy contributes to the cytotoxicity of MML in cancer cells harboring wild-type p53. This study strongly suggests that MML is a potential candidate for an anticancer agent targeting both autophagy and apoptotic cell death in human lung cancer. Moreover, co-treatment of MML and p53 inhibitor would be more effective in human lung cancer therapy.

Phytochemical profile of Paulownia tomentosa (Thunb). Steud

Paulownia tomentosa, a member of the plant family Paulowniaceae and a rich source of biologically active secondary metabolites, is traditionally used in Chinese herbal medicine. Flavonoids, lignans, phenolic glycosides, quinones, terpenoids, glycerides, phenolic acids, and miscellaneous other compounds have been isolated from different parts of P. tomentosa plant. Recent interest in this species has focused on isolating and identifying of prenylated flavonoids, that exhibit potent antioxidant, antibacterial, and antiphlogistic activities and inhibit severe acute respiratory syndrome coronavirus papain-like protease. They show cytotoxic activity against various human cancer cell lines and inhibit the effects of human cholinesterase, butyrylcholinesterase, and bacterial neuraminidases. Most of the compounds considered here have never been isolated from any other species of plant. This review summarizes the information about the isolated compounds that are active, their bioactivities, and the structure-activity relationships that have been worked out for them.

Advanced research on acteoside for chemistry and bioactivities

Acteoside is one kind of phenylethanoid glycoside, which has shown a lot of biological activities. This article reviewed the study progress of acteoside, such as distribution, preparation, identification, and bioactivities.

Antiradical and cytoprotective activities of several C-geranyl-substituted flavanones from Paulownia tomentosa fruit

Antiradical and cytoprotective activities of several flavanones isolated from Paulownia tomentosa (Thunb.) Steud. (Scrophulariaceae) have been evaluated using different in vitro and in vivo methods. The capacity of flavanones to scavenge radicals was measured in vitro by means of DPPH and ABTS assays, the inhibition of hydroxyl radicals produced in Fenton reactions, FRAP, scavenging superoxide radicals using enzymatic and nonenzymatic assays and the inhibition of peroxynitrite-induced nitration of tyrosine. The in vivo testing involved measuring the cytoprotective effect of chosen flavanones against alloxan-induced diabetes in mice. The activity of tested compounds was expressed either as a Trolox^® equivalent or was compared with rutin or morine as known antioxidant compounds. The highest activity in most tests was observed for diplacone and 3´-O-methyl-5´-hydroxydiplacone, and the structure vs. the antioxidant activity relationship of geranyl or prenyl-substituted flavonoids with different substitutions at the B and C ring was discussed.

Anti-herbivore structures of Paulownia tomentosa: morphology, distribution, chemical constituents and changes during shoot and leaf development

BACKGROUND AND AIMS

Recent studies have shown that small structures on plant surfaces serve ecological functions such as resistance against herbivores. The morphology, distribution, chemical composition and changes during shoot and leaf development of such small structures were examined on Paulownia tomentosa.

METHODS

The morphology and distribution of the structures were studied under light microscopy, and their chemical composition was analysed using thin-layer chromatography and high-performance liquid chromatography. To further investigate the function of these structures, several simple field experiments and observations were also conducted.

KEY RESULTS

Three types of small structures on P. tomentosa were investigated: bowl-shaped organs, glandular hairs and dendritic trichomes. The bowl-shaped organs were densely aggregated on the leaves near flower buds and were determined to be extrafloral nectarines (EFNs) that secrete sugar and attract ants. Nectar production of these organs was increased by artificial damage to the leaves, suggesting an anti-herbivore function through symbiosis with ants. Glandular hairs were found on the surfaces of young and/or reproductive organs. Glandular hairs on leaves, stems and flowers secreted mucilage containing glycerides and trapped small insects. Secretions from glandular hairs on flowers and immature fruits contained flavonoids, which may provide protection against some herbivores. Yellow dendritic trichomes on the adaxial side of leaves also contained flavonoids identical to those secreted by the glandular hairs on fruits and flowers. Three special types of leaves, which differed from the standard leaves in shape, size and identity of small structures, developed near young shoot tips or young flower buds. The density of small structures on these leaf types was higher than on standard leaves, suggesting that these leaf types may be specialized to protect young leaves or reproductive organs. Changes in the small structures during leaf development suggested that leaves of P. tomentosa are primarily protected by glandular hairs and dendritic trichomes at young stages and by the EFNs at mature stages.

CONCLUSIONS

The results indicate that P. tomentosa protects young and/or reproductive organs from herbivores through the distribution and allocation of small structures, the nature of which depends on the developmental stage of leaves and shoots.