Phenylethanoid Glycosides Verbascoside Research Articles

Verbascoside and rare flavone glucosides from Citharexylum spinosum L. flowers as antihyperglycemic agents: Isolation, α-amylase inhibition, molecular docking and drug-likeness prediction

Human concern for its public health has been a cornerstone since ancient times, with humans exploring natural resources in their environment for medicinal purposes. Plants have long served as the primary source of medicinal compounds, reflecting centuries of exploration and experimentation. Today, leveraging cognitive and technological advancements, researchers continue to deepen their studies towards achieving optimal health conditions. In pursuit of antihyperglycemic phyto-alternatives, a phytochemical investigation of EtOAc and n-BuOH flower extracts of Citharexylum spinosum L. yielded four rare flavone glucosides viz. cirsilineol 4′-glucoside, jaceoside, 5,4′-dihydroxy-7,3′-dimethoxyflavone 6-glucoside and pedaliin. Additionally, the flavone aglycone apigenin, and the phenylethanoid glycoside verbascoside were isolated. The flavonoid compounds were isolated for the first time from C. spinosum tree. The extracts underwent silica gel column chromatography for simplification, followed by compound purification using preparative HPLC. Molecular structures were elucidated through NMR spectroscopic experiments, spectrometric ESI-HRMS analysis, and comparisons with existing literature data. Subsequently, extracts and isolated compounds were evaluated for their antihyperglycemic activities by assessing their ability to inhibit α-amylase enzymatic activity. EtOAc and n-BuOH extracts displayed important anti-α-amylase properties with IC50 values of 52.5 ± 1.2 and 36.3 ± 1.1 µg/mL, respectively. The results demonstrated promising inhibitory properties of the α-amylase enzyme by the polyphenols isolated in this study. IC50 values ranged from 12.8 ± 0.1 to 23.2 ± 0.1 µM for the isolated compounds, comparable to the reference standard acarbose (IC50= 12.3 ± 0.1 µM). Furthermore, a structure-activity relationship study was conducted, with all isolated molecules docked to the α-amylase enzyme (PDB: 7TAA) and their drug-likeness properties predicted.

Phenylethanoid glycoside verbascoside ameliorates podocyte injury of diabetic kidney disease by regulating NR4A1-LKB1-AMPK signaling

Diabetic kidney disease (DKD) is one of the leading causes of end-stage renal disease. Verbascoside is a ubiquitous phenylethanoid glycoside with potent anti-inflammatory, antioxidant, and hypoglycemic properties. This study determined the renoprotective effect of verbascoside against DKD, as well as the underlying mechanism. After administration of verbascoside for 4 consecutive weeks, the fasting blood glucose level, albumin:creatinine ratio, and podocyte damage in diabetic mice were alleviated, especially at a dose of 150 mg/kg/d. Moreover, the inflammatory response, cell apoptosis, and autophagy were improved in a dose-dependent fashion in the kidneys of diabetic mice and high glucose-stimulated podocytes. Verbascoside reversed the elevated NR4A1 expression and suppressed LKB1 to inhibit AMPKα phosphorylation. Silencing NR4A1 inhibited LKB1 and phospho-AMPKα expression, and relieved the stress response in injured podocytes. Taken together, our results indicated that verbascoside alleviates DKD-associated podocyte injury by regulating NR4A1-LKB1-AMPK signaling.

Leucosceptoside A from Devil's Claw Modulates Psoriasis-like Inflammation via Suppression of the PI3K/AKT Signaling Pathway in Keratinocytes.

Psoriasis is a chronic inflammatory skin condition characterized by abnormal keratinocyte proliferation and differentiation that is accompanied with dysregulated immune response and abnormal vascularization. Devil’s claw (Harpagophytum procumbens (Burch.) DC. ex Meisn.) tubers extract has been used both systemically and topically for treatment of chronic inflammatory diseases such as arthritis, osteoporosis, inflammatory bowel disease, among others. However, its potential mechanisms of action against psoriasis remains poorly investigated. The human keratinocyte HaCaT cell line is a well-accepted in vitro model system for inflammatory skin disorders such as psoriasis. The present study involved an exploration of the effect of biotechnologically produced H. procumbens (HP) cell suspension extract and pure phenylethanoid glycosides verbascoside (VER) and leucosceptoside A (LEU) in interferon (IFN)-γ/interleukin (IL)-17A/IL-22-stimulated HaCaT cells as a model of psoriasis-like inflammation. Changes in key inflammatory signaling pathways related to psoriasis development were detected by reverse transcription polymerase chain reaction and western blotting. Treatment with LEU, but not VER and HP extract improved psoriasis-related inflammation via suppression of the PI3K/AKT signaling in IFN-γ/IL-17A/IL-22-stimulated HaCaT cells. Our results suggest that LEU may exhibit therapeutic potential against psoriasis by regulating keratinocyte differentiation through inhibition of the PI3K/AKT pathway.

Evaluation of in vitro antiprotozoal activity of Ajuga laxmannii and its secondary metabolites

Context Some Ajuga L. (Lamiaceae) species are traditionally used for the treatment of malaria, as well as fever, which is a common symptom of many parasitic diseases.Objective In the continuation of our studies on the identification of antiprotozoal secondary metabolites of Turkish Lamiaceae species, we have investigated the aerial parts of Ajuga laxmannii.Materials and methods The aerial parts of A. laxmannii were extracted with MeOH. The H2O subextract was subjected to polyamide, C18-MPLC and SiO2 CCs to yield eight metabolites. The structures of the isolates were elucidated by NMR spectroscopy and MS analyses. The extract, subextracts as well as the isolates were tested for their in vitro antiprotozoal activities against Plasmodium falciparum, Trypanasoma brucei rhodesiense, T. cruzi and Leishmania donovani at concentrations of 90–0.123 μg/mL.Results Two iridoid glycosides harpagide (1) and 8-O-acetylharpagide (2), three o-coumaric acid derivatives cis-melilotoside (3), trans-melilotoside (4) and dihydromelilotoside (5), two phenylethanoid glycosides verbascoside (6) and galactosylmartynoside (7) and a flavone-C-glycoside, isoorientin (8) were isolated. Many compounds showed moderate to good antiparasitic activity, with isoorientin (8) displaying the most significant antimalarial potential (an IC50 value of 9.7 μg/mL).Discussion and conclusion This is the first report on the antiprotozoal evaluation of A. laxmannii extracts and isolates. Furthermore, isoorientin and dihydromelilotoside are being reported for the first time from the genus Ajuga.

Phytochemical study of Capraria biflora L. aerial parts (Scrophulariaceae) from Martinique island (French West Indies)

Aerial parts of Capraria biflora L. were collected in Martinique (French West Indies) and extracted by methanol. Two original chlorinated iridoids, 3-hydroxymyopochlorin (1) and 5-hydroxyglutinoside (2) were isolated by CPC (centrifugal partition chromatography) and characterized from the extract together with five known iridoid glycosides (3–7), two flavonoid glucuronides (8–9) and the phenylethanoid glycoside verbascoside (10). The structure of these compounds together with their relative configuration was established by spectroscopic data including in particular 1D and 2D NMR experiments (HSQC, HMBC, NOESY) and HRESIMS. Preliminary antibacterial evaluation of 1, 2 and 3 against a panel of Gram-positive and Gram-negative strains has been performed.

Further iridoid glucosides in the genus Manulea (Scrophulariaceae)

From Manulea altissima (Scrophulariaceae) were isolated five known secoiridoid glucosides sweroside, eustomoside, eustoside, secoxyloganin and secologanoside as well as the 4″-O-rhamnopyranosyl-feruloyl ester of adoxosidic acid, named altissimoside. Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. In addition two previously unknown terpenoid esters of 6β-hydroxy 8-epi-boschnaloside, named manucoside A and B were isolated from a formerly obtained fraction from the work-up of Manulea corymbosa. The distribution of iridoid glucosides in the Scrophulariaceae is discussed.

Inhibition of the DHT-induced PSA secretion by Verbascum xanthophoeniceum and Serenoa repens extracts in human LNCaP prostate epithelial cells

Ethnopharmacological relevanceVerbascum xanthophoeniceum is a mullein plant, typical of Balkan region and some parts of Turkey, traditionally used as phytotherapeutic agent due to its anti-inflammatory properties. It is rich in phenylethanoid and iridoid metabolites whose anti-inflammatory properties are under characterization. Materials and methodsThe role of Verbascum xanthophoeniceum crude methanolic extract and its isolated phenylethanoid glycoside verbascoside have been evaluated, in comparison to a saw palmetto extract, on a human in vitro model of androgen-regulated prostate epithelium, the LNCaP cell line. Cytotoxicity and DHT-induced free and total PSA secretion have been thoroughly studied. ResultsWe have found that similar to saw palmetto, Verbascum xanthophoeniceum extract and its isolated phenylethanoid glycoside verbascoside have no cytotoxicity in human LNCaP prostate epithelial cells, whereas an inhibitory effect on the DHT-induced free and total PSA secretion, a recognized anti-androgen like activity, has been shown in case of both Verbascum xanthophoeniceum extract and pure verbascoside. Furthermore, in the absence of the endogenous androgen DHT, an androgen-like activity in Verbascum xanthophoeniceum is detectable as it is for saw palmetto, suggesting that a mixed androgen-antiandrogen activity is present. ConclusionsFor the first time, Serenoa repens and Verbascum xanthophoeniceum extracts have shown an absence of cytotoxicity and an inhibitory effect on DHT-induced PSA secretion in an in vitro model of human prostate epithelium, whereas the phenylethanoid glycoside verbascoside appeared to explain only part of the Verbascum xanthophoeniceum inhibitory activity on PSA secretion.

Inhibitory effect of the methanolic extract of Verbascum latisepalum Hub.-Mor. on endothelium-dependent relaxation in rat thoracic aorta.

The leaves and flowers of Verbascum species are used to treat respiratory disorders, haemorrhoids, rheumatic pain, and wounds as well as for the treatment of eczema and other types of inflammatory skin conditions in traditional Turkish medicine. We examined the effect of the methanolic extract of the aerial parts of Verbascum latisepalum Hub.-Mor. on the endothelium-dependent relaxation response in rat aortic rings which is mediated by nitric oxide (NO). Six fractions, A-F, were obtained from the methanolic extract through bioassay-guided fractionation procedures. The phenylethanoid glycoside verbascoside was isolated from fraction D and its structure elucidated by spectral techniques. The inhibitory effects of the extract, its fractions, and verbascoside on the acetylcholine-induced relaxation response in phenylephrine-precontracted aorta was examined in the absence and presence of L-arginine, a precursor in the synthesis of NO. The observation that the effects of the methanolic extract, of fraction D, and of verbascoside were reversed by L-arginine, indicates that verbascoside has an inhibitory effect on the synthesis of NO. This effect should be taken into consideration in view of the wide range of uses of Verbascum species in Turkish folk medicine.

Unexpected Secoiridoid Glucosides from Manulea corymbosa

From an extract of Manulea corymbosa were isolated four known secoiridoid glucosides (1-4), 10 new monoterpenoid esters of secologanol, namely, manuleosides A-I (5-11, 13, and 14) and dimethyl rhodanthoside A (12), and four new phenylpropanoid esters of carbocyclic iridoid glucosides, manucorymbosides I-IV (15-18). Also, the caffeoyl phenylethanoid glycoside verbascoside was isolated. The presence of secoiridoids apparently derived from loganic acid in the family Scrophulariaceae is unprecedented and greatly unexpected.

Quantitative determination of bioactive phenylethanoid glycosides in Clerodendrum phlomidis using HPTLC

A new validated high performance thin layer chromatographic method has been developed for the simultaneous determination of three bioactive phenylethanoid glycosides verbascoside (1), leucosceptoside A (2) and martynoside (3) in the roots of Clerodendrum phlomidis. Extraction efficiency of marker compounds was studied using normal (cold and hot), ultrasonic as well as microwave assisted extraction techniques with various solvents. Well resolved separation of marker compounds was achieved on silica gel 60F254 plates using the mobile phase consisting of chloroform–methanol–water (7.8:2.0:0.2, v/v/v). Quantitation of marker compounds was carried out using the densitometric reflection/absorption mode at 460 nm after post-chromatographic derivatization with vanillin–sulphuric acid reagent. Method was validated for peak purity, precision, robustness and sensitivity etc., as per ICH guidelines. Report on the occurrence of phenylethanoid glycosides for the first time in C. phlomidis is of chemotaxonomic importance.

Verbascum xanthophoeniceum-derived phenylethanoid glycosides are potent inhibitors of inflammatory chemokines in dormant and interferon-gamma-stimulated human keratinocytes

Ethnopharmacological relevanceVerbascum xanthophoeniceum is a representative of mullein species with a strong tradition of use in folk medicine as a remedy in inflammatory and infectious contexts. This plant accumulates phenylethanoid and iridoid metabolites with a partially characterized bioactivity. Materials and methodsHere, we compared anti-inflammatory effects of Verbascum xanthophoeniceum crude extract, its fractions, isolated iridoid glycosides, including aucubin, ajugol, harpagide, harpagoside, nigroside III and nigroside VI, and phenylethanoid glycosides verbascoside and forsythoside B in primary cultures of normal human keratinocytes (NHK). The gene expression, synthesis, and release of soluble pro-inflammatory chemokines, such as IL-8, MCP-1 and IP-10, in dormant and IFN-γ−activated NHK were investigated, and IC50 for each extract/individual substance was determined. ResultsWe found that the phenylethanoid glycosides verbascoside and forsythoside B were effective, dose-dependent inhibitors of gene expression and de novo synthesis of all the chemokines, whereas the iridoid glycosides and phenylpropanoid aglycone rosmarinic acid displayed a poor and selective inhibition. Accordingly, the fraction of the crude extract containing verbascoside effectively impaired both spontaneous and induced chemokine expression in NHK. ConclusionThis is the first report on the identification of active constituents of Verbascum xanthophoeniceum possessing anti-inflammatory properties towards human keratinocytes. Phenylethanoid glycosides exerted exquisite corticosteroid-like inhibition of pro-inflammatory chemokines at transcriptional and translational levels.

Sonication-assisted Agrobacterium rhizogenes-mediated transformation of Verbascum xanthophoeniceum Griseb. for bioactive metabolite accumulation

An efficient protocol for the establishment of transformed root culture of Verbascum xanthophoeniceum using sonication-assisted Agrobacterium rhizogenes-mediated transformation is reported. Only 10days after the inoculation with A. rhizogenes ATCC 15834 and 45s ultrasound exposure, hairy roots appeared on 75% of the Verbascum leaves. Ten hairy root lines were isolated, although only half of them were free of bacterial contamination and started growing when excised from mother explants. The transgenic nature of the most vigorously growing hairy root clones (VX1 and VX6) was confirmed by polymerase chain reaction. Under submerged cultivation both hairy root clones accumulated high biomass amounts (12.8 and 14.3gL(-1), respectively) and significant amounts of bioactive phenylethanoid glycoside verbascoside (over 6-times more than in mother plant leaves). LC-APCI-MS analyses confirmed verbascoside accumulation in hairy root clones along with three other phenylethanoid glycosides (forsythoside B, leucosceptoside B and martynoside) and an iridoid glycoside aucubin. This is the first report on the induction of hairy roots of Verbascum plants.

Anti-inflammatory activity of Devil’s claw in vitro systems and their active constituents

Cell suspension and Agrobacterium rhizogenes-transformed hairy root cultures of Devil’s claw ( Harpagophytum procumbens), an African plant with high medicinal value, were cultivated in shake-flasks. A purification scheme to isolate their main active constituents (the phenylethanoid glycosides verbascoside, leucosceptoside A, β-OH-verbascoside and martynoside; structurally identified by NMR and LC–MS) was then developed, and their concentrations in the cultures were determined by UV spectrometry following HPLC separation. Preparations, extracts and the isolated phenylethanoid glycosides from the H. procumbens in vitro systems were tested on isolated murine macrophages to study their effects on nitric oxide (NO) and cytokine (TNF-α, IL-6) release and the expression of COX-1 and COX-2. They were also added to human serum to investigate their effects on the classical pathway of complement activation. The results indicate that the extracts and preparations of the in vitro systems, and pure verbascoside (their main active constituent), had strong anti-inflammatory properties, comparable to or even higher than that of pure harpagoside (a major anti-inflammatory constituent of intact Devil’s claw tubers). Thus, they have potential as new anti-inflammatory agents.

Potential bioactive phenolics of Macedonian Sideritis species used for medicinal “Mountain Tea”

Twenty four phenolic compounds have been characterised in medicinal Sideritis species (aerial parts) from Macedonia by liquid chromatography–UV diode array coupled to ion-trap mass spectrometry with electrospray ionisation interface (negative mode). Three new phenylethanoid glycosides, alyssonoside, echinacoside, and forsythoside were detected for the first time in the genus of Sideritis, along with two known phenylethanoid glycoside verbascoside and leucoseptoside A. Three hydroxycinnamic acids, such as, 3-caffeoylquinic acid, 5-caffeoylquinic acid and feruloylquinic acid, five flavonoid 7- O-diglycosides of apigenin, hypolaetin, 3′- O-methylhypolaetin, isoscutellarein and 4′- O-methylisoscutellarein and 11 acetylated flavonoid 7- O-diglycosides. The phenolic profile of different parts of two wild and cultivated grown Sideritis species from Macedonia has been analysed using water and methanol extracts to give an insight of the nature of the flavonoids in their glycosylated forms and combinations with phenolic acids present in the plants. The structures of flavonoid glycosides were analysed before and after alkaline hydrolysis. The effect of sugar substitution and acetylation on the flavonoids and ESI ionisation and fragmentation are discussed.

South African Lippia herbal infusions: Total phenolic content, antioxidant and antibacterial activities

Lippia javanica and Lippia scaberrima are used as herbal remedies and are commercially traded as health teas in southern Africa under the brands “Mosukujane” and “Musukudu”, respectively. This study evaluates the relationship between the presence of phenolic compounds and the antioxidant activities of infusions prepared from four Lippia species ( L. javanica, L. scaberrima, L. rehmannii and L. wilmsii) indigenous to South Africa. The antioxidant activities of the infusions, determined by the 2,2-diphenylpycrylhydrazyl (DPPH) method, were also compared to those of popular black, green and herbal tea brands. Of the four indigenous species, infusions of L. javanica and L. wilmsii exhibited the highest antioxidant activities (EC 50: 358 and 525 µg/ml, respectively) and contained the most phenolic compounds (14.8 and 14.5 mg/ml of dry weight gallic acid equivalent, respectively). Antibacterial activities of methanolic extracts of the four Lippia species were determined against four human pathogens ( Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). The extract of L. javanica was the most active against all the pathogens tested. Those Lippia species ( L. javanica and L. wilmsii) previously reported to produce higher levels of the pharmacologically active phenylethanoid glycosides verbascoside and isoverbascoside, portrayed stronger antioxidant and antibacterial activities. This study gives credence to the use of infusions of these Lippia species for their general health benefits.

The effect of verbascoside on cyclic 3′,5′-adenosine monophosphate levels in isolated rat heart

The effects mediated by the naturally occurring phenylethanoid glycoside verbascoside (1 mM) in isolated rat hearts (significant increases in heart rate (42%), contractile force (13%) and coronary perfusion rate (113%)) all coincided with a marked increase in intracellular levels of cyclic-3′,5′-adenosine monophosphate (1733% increase).