Inhibitory Effect of Verbascoside Isolated from Buddleja brasiliensis Jacq. ex Spreng on Prolyl Oligopeptidase Activity

Verbascoside: comprehensive review of a phenylethanoid macromolecule and its journey from nature to bench

Polyphenolic compounds are among the most widely researched compounds for various therapeutic applications. However, naturally occurring phenylethanoid glycosides are least explored under this class of compounds. One such phenylethanoid glycoside, verbascoside (Vb), abundantly found among 200 species of 23 families, has gained recent attention due to its wide-spectrum therapeutic properties such as antioxidant, antimicrobial, anti-inflammatory, neuroprotective, cardioprotective, skin-protective, and anti-cancer. Despite having multiple therapeutic benefits, due to its large size, the compound has poor bioavailability for oral and topical applications. To meet these limitations, current research on Vb focuses on delivering it through nanoformulations. Presently, most developed formulations are liposome based for various applications, such as corneal epithelial wound healing, anti-neuropathic, anti-wrinkle, anti-hyperalgesia, atopic dermatitis, alopecia, and cutaneous wound healing. Multiple studies have confirmed the least acute and sub-acute toxicity for Vb. Few clinical studies have been performed for the therapeutic application of Vb to manage COVID-19, nephropathy, platelet aggregation, chronic primary glomerulonephritis, and acute hepatitis. Recent studies have shown the immense therapeutic potential of Vb in wound healing, dermatitis, neuroprotection, and anti-cancer activities, which creates a need for developing novel formulations for their respective uses. Long-term toxicity studies and techniques for scaling up Vb production by biotechnological approaches should be emphasized.

Copper exposure leads to changes in chlorophyll content and secondary metabolite profile in Lantana fucata leaves

Cultivation of plants in environments polluted by metals at toxic levels can affect the biosynthesis of secondary metabolites. Here, we analysed the effect caused by excess copper on the concentration of chlorophylls a and b and the profile of secondary metabolites of Lantana fucata leaves. Five copper (Cu) treatments (mg Cukg-1 soil) were tested: T0, 0; T1, 210; T2, 420; T3, 630; and T4, 840. We found that the concentrations of chlorophylls in the plants decreased when compared to the control. However, this did not lead to a significant reduction in its growth, possibly due to the low translocation of the metal to shoots and the activation of plant defence systems to tolerate the environment in which they are exposed, increasing the emission of lateral roots and activating pathways for the production of secondary metabolites. Therefore, we found a decrease in the concentration of two key compounds in secondary metabolism, p -coumaric and cinnamic acids in treatments with higher copper concentrations. We also found an increase in phenolics. Decreases in p -coumaric and cinnamic acids may have occurred because these are precursors in the synthesis of phenolic compounds, which are increased in the high Cu treatments. Six secondary metabolites were characterised, described for the first time for this plant species. Thus, the presence of excess Cu in the soil may have triggered an increase in the amount of reactive oxygen species in the plants, which that led to the synthesis of antioxidant compounds, as a defence strategy.

Diversification of phenolic glucosides by two UDP-glucosyltransferases featuring complementary regioselectivity

BACKGROUND

Glucoside natural products have been showing great medicinal values and potentials. However, the production of glucosides by plant extraction, chemical synthesis, and traditional biotransformation is insufficient to meet the fast-growing pharmaceutical demands. Microbial synthetic biology offers promising strategies for synthesis and diversification of plant glycosides.

RESULTS

In this study, the two efficient UDP-glucosyltransferases (UGTs) (UGT85A1 and RrUGT3) of plant origin, that are capable of recognizing phenolic aglycons, are characterized in vitro. The two UGTs show complementary regioselectivity towards the alcoholic and phenolic hydroxyl groups on phenolic substrates. By combining a developed alkylphenol bio-oxidation system and these UGTs, twenty-four phenolic glucosides are enzymatically synthesized from readily accessible alkylphenol substrates. Based on the bio-oxidation and glycosylation systems, a number of microbial cell factories are constructed and applied to biotransformation, giving rise to a variety of plant and plant-like O-glucosides. Remarkably, several unnatural O-glucosides prepared by the two UGTs demonstrate better prolyl endopeptidase inhibitory and/or anti-inflammatory activities than those of the clinically used glucosidic drugs including gastrodin, salidroside and helicid. Furthermore, the two UGTs are also able to catalyze the formation of N- and S-glucosidic bonds to produce N- and S-glucosides.

CONCLUSIONS

Two highly efficient UGTs, UGT85A1 and RrUGT3, with distinct regioselectivity were characterized in this study. A group of plant and plant-like glucosides were efficiently synthesized by cell-based biotransformation using a developed alkylphenol bio-oxidation system and these two UGTs. Many of the O-glucosides exhibited better PEP inhibitory or anti-inflammatory activities than plant-origin glucoside drugs, showing significant potentials for new glucosidic drug development.

Anti-Inflammatory Effects Induced by a Polyphenolic Granular Complex from Olive (Olea europaea, Mainly Cultivar coratina): Results from In Vivo and Ex Vivo Studies in a Model of Inflammation and MIA-Induced Osteoarthritis

MOMAST^® GR25 is a polyphenolic granular complex from olive pressing juice with high total content in polyphenols. In this work, we evaluated the possible anti-inflammatory effects of MOMAST^® GR25 in both acute and chronic inflammatory models. MOMAST^® GR25 decreased the levels of prostaglandin (PG) E₂ and 8-iso-PGF_2α in isolated rat colon, liver, and heart specimens stimulated with lipopolysaccharide (LPS). In vivo, compared to controls, rats treated with MOMAST^® GR25 (100 mg/kg to 1 g/kg) showed a significant reduction in both licking/biting time in the formalin test. In a rat model of osteoarthritis by monoiodoacetate (MIA) injection, MOMAST^® GR25 showed pain-relieving properties when acutely administered, reducing mechanical hyperalgesia and spontaneous pain. Moreover, a repeated daily treatment with MOMAST^® GR25 (300 mg/kg) fully counteracted osteoarticular pain without the development of tolerance to the antinociceptive effect. Taken together, our present findings showed that MOMAST^® GR25 could represent a potential strategy for the treatment of inflammation and pain.

Cytotoxic Effects of Verbascoside on MCF-7 and MDA-MB-231

Objectives

Verbascoside, also known as acteoside/kusaginin, has attracted a great attention due to its pharmacological features. In this study, we aimed to determine the cytotoxic effects of pure verbascoside isolated from Phlomis nissolii L. plant in both MCF-7 and MDA-MB-231 cell lines in vitro.

Materials and Methods

MCF-7 and MDA-MB 231 cells were treated with verbascoside (100, 48, 25, 10, 1, 0.5, and 0.1 μM) for 24, 48, and 72 hours. Cytotoxic effect of verbascoside in MCF-7 and MDA-MB-231 cells was assessed using TEBU-BIO cell counting kit 8.

Results and Conclusion

IC₅₀ values for 24, 48, and 72 h verbascoside exposure of MCF-7 cells were determined as 0.127, 0.2174, and 0.2828 μM, respectively. R² values were calculated as 0.9630, 0.8789 and 0.8752, respectively. Two-Way ANOVA multiple comparison test results showed that 100 μM verbascoside has the highest cytotoxic effect on MCF-7 breast cancer (BC) cells after 72 h of exposure. IC₅₀ values for 24, 48 and 72 h verbascoside exposure of MDA-MB 231 cells were determined as 0.1597, 0.2584 and 0.2563 μM, respectively and R² values were calculated as 0.8438, 0.5107 and 0.9203, respectively. Two-Way ANOVA multiple comparisons test results showed that 100 μM verbascoside has the highest cytotoxic effect on MDA-MB 231 BC cells after 24, 48 and 72 h of exposure.

Biological effects of verbascoside and its anti-inflammatory activity on oral mucositis: a review of the literature

Oral mucositis is among the most common tissue toxicities associated with both cytotoxic cancer regimens and head and neck radiotherapy. Current management of oral mucositis might comprise growth factors and cytokines, anti-inflammatory agents, anesthetics, analgesics, antimicrobial and coating agents, cryotherapy and mucosal protectants. Despite its long history and its impact on patients, there are currently no effective options for the prevention or treatment of mucositis. In recent years, more attention has been focused on the role of natural drugs. Verbascoside belongs to the phenylpropanoid glycosides family. Several biological properties have been described, such as anti-inflammatory, antimicrobial, antitumor and antioxidant. Verbascoside, particularly when in solution with polyvinylpyrrolidone and sodium hyaluronate, thanks to barrier effect, is useful in re-epithelialization and in reducing pain, oral mucositis score, burning and erythema.

A review on the structure and pharmacological activity of phenylethanoid glycosides

Phenylethanoid glycosides (PhGs) are compounds made of phenylethyl alcohol, caffeic acid and glycosyl moieties. The first published references about phenylethanoid glycosides concerned the isolation of echinacoside from Echinaceu ungustifolia (Asteraceae) in 1950 and verbascoside from Verbascum sinuatum (Scrophulariaceae) in 1963. Over the past 60 years, many compounds with these structural characteristics have been isolated from natural sources, and most of these compounds possess significant bioactivities, including antibacterial, antitumor, antiviral, anti-inflammatory, neuro-protective, antioxidant, hepatoprotective, and immunomodulatory activities, among others. In this review, we will summarize the phenylethanoid glycosides described in recent papers and list all the compounds that have been isolated over the past few decades. We will also attempt to present and assess recent studies about the separation, extraction, determination, and pharmacological activity of the excellent natural components, phenylethanoid glycosides.

The TLC-Bioautography as a Tool for Rapid Enzyme Inhibitors detection - A Review

Microorganisms and plants can be important sources of many compounds with potential pharmaceutical applications. Extraction of these matrices is one of the ways of identifying the presence of inhibitory active substances against enzymes whose high activity leads to serious human diseases including cancer, Parkinson's or Crohn's diseases. The isolation and purification of inhibitors are time-consuming and expensive steps in the analysis of the crude extract and therefore, it is necessary to find a fast, efficient, and inexpensive method for screening extracts of interest. TLC-Bioautography combines the separation of the extract on a thin layer with its subsequent biological analysis. TLC-Bioautography methods have been developed for several classes of enzymes including oxidoreductases, hydrolases and isomerases, and there is a potential for developing functional methods for other classes of enzymes. This review summarizes known TLC-Bioautography methods and their applications for determining the presence of enzyme inhibitors in extracts and compares the effectiveness of different methodological approaches. It also indicates the current state and perspective of the development of TLC-Bioautography and its possible future applications.

Purification of Phenylpropanoids from the Scaly Bulbs of Lilium Longiflorum by CPC and Determination of Their DPP-IV Inhibitory Potentials

The scaly bulbs of Lilium longiflorum (Liliaceae) are used as a food ingredient and a traditional medicine in East Asia. A preliminary study revealed that treatment with 100 μg/mL of the ethyl acetate fraction of this plant material inhibited dipeptidyl peptidase IV (DPP-IV) to 58.99%. Phytochemical studies were conducted to identify the active ingredient, and five compounds, namely, 1 (2.9 mg, 75.8% purity at 320 nm), 2 (12.2 mg, 97.9% purity at 320 nm), 3 (3.1 mg, 66.5% purity at 320 nm), 4 (6.8 mg, 96.9% purity at 320 nm), and 5 (6.2 mg, 90.2% purity at 320 nm) were purified from 200 mg of the ethyl acetate fraction of L. longiflorum via centrifugal partition chromatography (CPC) with a two-phase solvent system composed of chloroform/methanol/isopropanol/water (5:2:2:4, v/v/v/v) in an ascending mode. Their structures were identified as 1-O-p-coumaroyl-2-O-β-glucopyranosylglycerol (regaloside D, 1), 3,6'-O-diferuloylsucrose (2), 1-O-p-coumaroyl-2-O-β-glucopyranosyl-3-O-acetylglycerol (regaloside B, 3), 1-O-p-coumaroylglycerol (4), and 4-O-acetyl-3,6'-O-diferuloylsucrose (5), respectively, by ¹H and ¹³C NMR and MS analysis. Compounds 2 and 5 exhibited DPP-IV inhibitory activities with IC₅₀ values of 46.19 and 63.26 μM, respectively. Compounds 1, 3, and 4 did not show activities, indicating that biphenylpropanoids linked via the sugar moiety are more effective than phenylpropanoids with glycerol or glyceryl glucoside. This is the first report of simultaneous separation of five phenylpropanoids from L. longiflorum by CPC and evaluation of their DPP-IV inhibitory activities.

Evaluation of prolyl oligopeptidase and acetylcholinesterase inhibition by Phyllanthus tenellus Roxb. from Brazil

Phyllanthus tenellus Roxb. (Phyllanthaceae) is a plant used in Brazilian folk medicine for the treatment of intestinal infections and diabetes. Despite its use in traditional medicine, it was reported that P. tenellus extract may cause several effects in the central nervous system (CNS) of animals, such as agitation and signs of depression. The aim of this study was to determine the main constituents of P. tenellus methanol extract and to investigate whether the extract is able to inhibit the enzymes prolyl oligopeptidase (POP), acetylcholinesterase (AChE) and dipeptidyl peptidase-IV (DPP-IV). Corilagin (1) was isolated as the main constituent of the P. tenellus extract, along with rutin (2) and vitexin-2″-O-rhamnoside (3). The extract presented the ability to inhibit mainly POP. Dichloromethane and ethyl acetate fractions showed the highest inhibitory potency against POP (IC₅₀ values of 1.7 ± 0.4 and 11.7 ± 2 µg/mL, respectively). All fractions were inactive against AChE. Corilagin displayed selective POP inhibition in a dose-dependent manner, with IC₅₀= 19.7 ± 2.6 µg/mL. Corilagin exhibited moderate capacity to pass through the phospholipid membrane by passive diffusion, presenting effective permeability (Pe) of 1.26 × 10^-7 cm/s.

Prolyl oligopeptidase and its role in the organism: attention to the most promising and clinically relevant inhibitors

Prolyl oligopeptidase (POP), also called prolyl endopeptidase, is a cytosolic enzyme investigated by several research groups. It has been proposed to play an important role in physiological processes such as modulation of the levels of several neuronal peptides and hormones containing a proline residue. Due to its proteolytic activity and physiological role in cell signaling pathways, inhibition of POP offers an emerging approach for the treatment of Alzheimer's and Parkinson's diseases as well as other diseases related to cognitive impairment. Furthermore, it may also represent an interesting target for treatment of neuropsychiatric disorders, and as an antiangiogenesis or antineoplastic agent. In this review paper, we summarized naturally occurring POP inhibitors together with peptide-like inhibitors and their biological effects. Some of them have shown promising results and interesting pharmacological profiles. However, to date, there is no POP inhibitor available on the market although several clinical trials have been undertaken.

Polyphenol compounds and PKC signaling

BACKGROUND

Naturally occurring polyphenols found in food sources provide huge health benefits. Several polyphenolic compounds are implicated in the prevention of disease states, such as cancer. One of the mechanisms by which polyphenols exert their biological actions is by interfering in the protein kinase C (PKC) signaling pathways. PKC belongs to a superfamily of serine-threonine kinase and are primarily involved in phosphorylation of target proteins controlling activation and inhibition of many cellular processes directly or indirectly.

SCOPE OF REVIEW

Despite the availability of substantial literature data on polyphenols' regulation of PKC, no comprehensive review article is currently available on this subject. This article reviews PKC-polyphenol interactions and its relevance to various disease states. In particular, salient features of polyphenols, PKC, interactions of naturally occurring polyphenols with PKC, and future perspective of research on this subject are discussed.

MAJOR CONCLUSIONS

Some polyphenols exert their antioxidant properties by regulating the transcription of the antioxidant enzyme genes through PKC signaling. Regulation of PKC by polyphenols is isoform dependent. The activation or inhibition of PKC by polyphenols has been found to be dependent on the presence of membrane, Ca(2+) ion, cofactors, cell and tissue types etc. Two polyphenols, curcumin and resveratrol are in clinical trials for the treatment of colon cancer.

GENERAL SIGNIFICANCE

The fact that 74% of the cancer drugs are derived from natural sources, naturally occurring polyphenols or its simple analogs with improved bioavailability may have the potential to be cancer drugs in the future.

Verbascoside--a review of its occurrence, (bio)synthesis and pharmacological significance

Phenylethanoid glycosides are naturally occurring water-soluble compounds with remarkable biological properties that are widely distributed in the plant kingdom. Verbascoside is a phenylethanoid glycoside that was first isolated from mullein but is also found in several other plant species. It has also been produced by in vitro plant culture systems, including genetically transformed roots (so-called 'hairy roots'). Verbascoside is hydrophilic in nature and possesses pharmacologically beneficial activities for human health, including antioxidant, anti-inflammatory and antineoplastic properties in addition to numerous wound-healing and neuroprotective properties. Recent advances with regard to the distribution, (bio)synthesis and bioproduction of verbascoside are summarised in this review. We also discuss its prominent pharmacological properties and outline future perspectives for its potential application.