Methyl caffeate as an alpha-glucosidase inhibitor from Solanum torvum fruits and the activity of related compounds

In vitro and in silico analysis of Solanum torvum fruit and methyl caffeate interaction with cholinesterases

Oxidative stress along with dysfunction in cholinergic neurotransmission primarily underlies cognitive impairment. A significant approach to mitigate cognitive dysfunction involves the inhibition of cholinesterases, namely acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Exploring the potential antioxidant and anticholinesterase effects of edible plants holds promise for their utilization as botanicals to enhance cognition. Solanum torvum fruit with vast biological properties are used as food. In the present study, butanolic extract of S. torvum fruits (BESTF) was prepared. Additionally, the study investigated into the properties of methyl caffeate (MC), a compound present in S. torvum, obtained in its pure form. In vitro antioxidant and anticholinesterases activity of BESTF and MC were determined. BESTF and MC showed potent antioxidant property. BESTF and MC dose-dependently inhibited AChE (IC50 values: 166.6 µg/ml and 680.6 µM, respectively) and BChE (IC50 values: 161.55 µg/ml and 413 µM, respectively). BESTF and MC inhibited AChE and BChE in competitive mode. Active site gorge of AChE/BChE was occupied by MC which formed interaction with amino acids present in catalytic site and PAS in in silico. Further, molecular dynamics simulations followed by free energy calculation, principal component analysis and dynamic cross-correlation matrix provided the compelling evidence that that MC maintained stable interactions during MD simulation with AChE and BChE. Collectively, the results from the present study underlines the cognitive-enhancing effect of BESTF and MC.

Phytochemical Analysis, Anti-inflammatory, and Anticancer Activities of the Halophyte Herb Bassia indica

Bassia indica (Wight) A.J. Scott, family Amaranthaceae, is a halophyte herb growing in extreme environments and hence deemed as a potential economic source of bioactive chemicals with functional properties. In our study, 25 compounds were obtained from B. indica. We aimed to assess the inhibitory effect of the methanol extract of B. indica and its isolated compounds on COX-2 and cytotoxicity activity against MCF-7, OVK-18, HepG2, and HCT116 tumor cells. Among the isolates, the triterpene oleanane saponin (23) displayed promising anti-inflammatory activity with an IC50 = 3.05 ± 0.15 μg/mL. Additionally, N- trans-feruloyl tyramine (11) exhibited significant cytotoxicity to OVK-18 with IC50 = 1.74 ± 1.56 μg/mL, whereas 6,7-dihydroxy coumarin (7) exhibited potent inhibition against the MCF-7 cell line with IC50 = 1.47 ± 0.22 μg/mL. Interestingly, compounds 1 and 25 exhibited remarkable cytotoxicity against HepG2 and HCT116 cells with IC50 < 0.1 μg/mL, while compounds 2, 4, 5, 6, and 9 exerted potent cytotoxicity against HepG2. Finally, B. indica is a potential source of candidate compounds for the development of anti-inflammatory and antitumor therapies.

Solanum Fruits: Phytochemicals, Bioaccessibility and Bioavailability, and Their Relationship With Their Health-Promoting Effects

The Solanum genus is the largest in the Solanaceae family containing around 2,000 species. There is a great number of edibles obtained from this genus, and globally, the most common are tomato (S. lycopersicum), potato (S. tuberosum), and eggplant (S. melongena). Other fruits are common in specific regions and countries, for instance, S. nigrum, S. torvum, S. betaceum, and S. stramonifolium. Various reports have shown that flavonoids, phenolic acids, alkaloids, saponins, and other molecules can be found in these plants. These molecules are associated with various health-promoting properties against many non-communicable diseases, the main causes of death globally. Nonetheless, the transformations of the structure of antioxidants caused by cooking methods and gastrointestinal digestion impact their potential benefits and must be considered. This review provides information about antioxidant compounds, their bioaccessibility and bioavailability, and their health-promoting effects. Bioaccessibility and bioavailability studies must be considered when evaluating the bioactive properties of health-promoting molecules like those from the Solanum genus.

Approaches for the enzymatic synthesis of alkyl hydroxycinnamates and applications thereof

Alkyl hydroxycinnamates (AHs) is a group of molecules of biotechnological interest due to their cosmetic, food, and pharmaceutical applications. Among their most interesting uses are as UV protectants, skin depigmentation agents, and antioxidant ingredients which are often claimed for their antitumoral potential. Nowadays, many sustainable enzymatic approaches using low-cost starting materials are available and interesting immobilization techniques are helping to increase the reuse of the biocatalysts, allowing the intensification of the processes and increasing AHs accessibility. Here a convenient summary of AHs most interesting biological activities and possible applications is presented. A deeper analysis of the art state to obtain AHs, focusing on most employed enzymatic synthesis approaches, their sustainability, acyl donors relevance, and most interesting enzyme immobilization strategies is provided.Key points• Most interesting alkyl hydroxycinnamates applications are summarized.• Enzymatic approaches to obtain alkyl hydroxycinnamates are critically discussed.• Outlook of enzyme immobilization strategies to attain alkyl hydroxycinnamates.

Synthesis of Yakuchinone B-Inspired Inhibitors against Islet Amyloid Polypeptide Aggregation

Type 2 diabetes mellitus (T2DM) is associated with pancreatic β-cell dysfunction and insulin resistance. Islet amyloid polypeptide (IAPP) aggregation is found to induce islet β-cell death in T2DM patients. Recently, we demonstrated that yakuchinone B derivative 1 exhibited inhibitory activity against IAPP aggregation. Thus, in this study, a series of synthesized yakuchinone B-inspired compounds were tested for their anti-IAPP aggregation activity. Four of these compounds, 4e-h, showed greater activity than the lead compound 1, in the sub-μM range (IC₅₀ = 0.7-0.8 μM). The molecular docking analysis revealed crucial hydrogen bonds between the compounds and residues S19 and N22 and important hydrophobic interactions with residue I26. Notably, compounds 4g and 4h significantly protected β-cells against IAPP-induced toxicity with EC₅₀ values of 0.1 and 0.2 μM, respectively. In contrast, the protective activities of compounds 4e and 4f were weak. Overall, these results suggest that the compounds exhibiting IAPP aggregation-inhibiting activity have the potential to treat T2DM.

A novel acylated flavonol tetraglycoside and rare oleanane saponins with a unique acetal-linked dicarboxylic acid substituent from the xero-halophyte Bassia indica

In recent years, the scientific interest and particularly the economic significance of halophytic plants has been highly demanding due to the medicinal and nutraceutical potential of its bioactive compounds. A xero-halophyte Bassia indica is deemed to be a very cheap source of natural entities without chemical or biological investigation. In this context, a new acylated flavonol tetraglycoside, kaempferol-3-O-β-d-glucopyranosyl-(1→6)-O-[β-D-galactopyranosyl-(1→3)-2-O-trans-feruloyl-α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (14), together with rare occurring flavonol triglycoside, isorhamnetin-3-O-β-d-glucopyranosyl-(1→6)-O-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (15), were isolated from the aqueous methanol extract of the aerial parts of B. indica. The study also reported an optimal separation and characterization of a new seco-glycosidic oleanane saponin with 2'R,3'S stereocenters, identified as (2'R,3'S)-3-O-[2'-hydroxy-3'-(2"-O-glycolyl)-oxo-propionic acid-β-D-glucuronopyranosyl]-28-O-β-D-glucopyranosyl-olean-12-en-3β-ol-28-oic acid (17), in addition to its derivative, 3-O-[2'-(2"-O-glycolyl)-glyoxylyl-β-D-glucuronopyranosyl]-28-O-β-d-glucopyranosyl-olean-12-en-3β-ol-28-oic acid (16). The structures of all isolated compounds were elucidated based on 1D, 2D NMR, and HR-MS analysis, as well as comparing with similar derivatives published in the literature. Furthermore, thirteen known compounds were isolated and identified as β-sitosterol (1), vanillic acid (2), o-hydroxybenzoic acid (3), р-hydroxybenzoic acid (4), 6,7-dihydroxycoumarin (5), methyl caffeate (6), caffeic acid (7), quercetin (8), uracil (9), thymidine (10), tachioside (11), isorhamnetin-3-O-β-D-glucopyranoside (12), kaempferol-3-O-rutinoside (13). The anticholinesterase activity of all isolated compounds was evaluated.

Caffeates and Caffeamides: Synthetic Methodologies and Their Antioxidant Properties

Polyphenols are secondary metabolites of plants and include a variety of chemical structures, from simple molecules such as phenolic acids to condensed tannins and highly polymerized compounds. Caffeic acid (3,4-dihydroxycinnamic acid) is one of the hydroxycinnamate metabolites more widely distributed in plant tissues. It is present in many food sources, including coffee drinks, blueberries, apples, and cider, and also in several medications of popular use, mainly those based on propolis. Its derivatives are also known to possess anti-inflammatory, antioxidant, antitumor, and antibacterial activities, and can contribute to the prevention of atherosclerosis and other cardiovascular diseases. This review is an overview of the available information about the chemical synthesis and antioxidant activity of caffeic acid derivatives. Considering the relevance of these compounds in human health, many of them have been the focus of reviews, taking as a center their obtaining from the plants. There are few revisions that compile the chemical synthesis methods, in this way, we consider that this review does an important contribution.

The Genus Solanum: An Ethnopharmacological, Phytochemical and Biological Properties Review

Over the past 30 years, the genus Solanum has received considerable attention in chemical and biological studies. Solanum is the largest genus in the family Solanaceae, comprising of about 2000 species distributed in the subtropical and tropical regions of Africa, Australia, and parts of Asia, e.g., China, India and Japan. Many of them are economically significant species. Previous phytochemical investigations on Solanum species led to the identification of steroidal saponins, steroidal alkaloids, terpenes, flavonoids, lignans, sterols, phenolic comopunds, coumarins, amongst other compounds. Many species belonging to this genus present huge range of pharmacological activities such as cytotoxicity to different tumors as breast cancer (4T1 and EMT), colorectal cancer (HCT116, HT29, and SW480), and prostate cancer (DU145) cell lines. The biological activities have been attributed to a number of steroidal saponins, steroidal alkaloids and phenols. This review features 65 phytochemically studied species of Solanum between 1990 and 2018, fetched from SciFinder, Pubmed, ScienceDirect, Wikipedia and Baidu, using "Solanum" and the species' names as search terms ("all fields").

Synthesis and Antioxidant Activity of Caffeic Acid Derivatives

A series of caffeic acid derivatives were synthesized via a modified Wittig reaction which is a very important tool in organic chemistry for the construction of unsaturated carbon⁻carbon bonds. All reactions were performed in water medium at 90 °C. The aqueous Wittig reaction worked best when one unprotected hydroxyl group was present in the phenyl ring. The olefinations in the aqueous conditions were also conducted with good yields in the presence of two unprotected hydroxyl groups. When the number of the hydroxyl groups was increased to three, the reaction yields were worse, and the derivatives 12, 13, and 18 were obtained with 74%, 37%, and 70% yields, respectively. Nevertheless, the Wittig reaction using water as the essential medium is an elegant one-pot synthesis and a greener method, which can be a safe alternative for implementation in organic chemistry. The obtained compounds were tested for their antioxidant activity, and 12, 13, and 18 showed the highest activities. Moreover, all synthesized compounds displayed no cytotoxicity, and can therefore be used in the pharmaceutical or cosmetic industry.

Methyl caffeate and some plant constituents inhibit age-related inflammation: effects on senescence-associated secretory phenotype (SASP) formation

During aging, cells secrete molecules called senescence-associated secretory phenotype (SASP). They constitute chronic low-grade inflammation environment to adjacent cells and tissues. In order to find inhibiting agents of SASP formation, 113 plant constituents were incubated with BJ fibroblasts for 6 days after treatment with bleomycin. Several plant constituents showed considerable inhibition of IL-6 production, a representative SASP marker. These plant constituents included anthraquinones such as aurantio-obtusin, flavonoids including astragalin, iristectorigenin A, iristectorigenin B, linarin, lignans including lariciresinol 9-O-glucoside and eleutheroside E, phenylpropanoids such as caffeic acid and methyl caffeate, steroid (ophiopogonin), and others like centauroside, rhoifolin and scoparone. In particular, methyl caffeate down-regulated SASP factors such as IL-1α, IL-1β, IL-6, IL-8, GM-CSF, CXCL1, MCP-2, and MMP-3. Inhibition of these SASP mRNA expression levels also coincided with the reduction of IκBζ expression and NF-κB p65 activation without affecting the expression levels of senescence markers, p21 or pRb. Taken together, the present study demonstrated that methyl caffeate might be a specific and strong inhibitor of SASP production without affecting the aging process. Its action mechanisms involve the reduction of IκBζ expression and NF-κB p65 activation. Therefore, this compound might be effective in alleviating chronic low-grade inflammation linked to age-related degenerative disorders.

Solanum torvum Swartz. fruit attenuates cadmium-induced liver and kidney damage through modulation of oxidative stress and glycosylation

Increased levels of environmental pollutants are linked to almost all human disorders; the efficient method to manage the human health is through naturally available dietary molecule. Solanum torvum (ST) Swartz (Solanaceae) commonly called Turkey Berry is found in Africa, Asia, and South America. Its fruit, part of traditional Indian cuisine, is a widely consumed nutritious herb, acclaimed for its medicinal value. ST aqueous extract (STAe) (250, 500, and 1000 mg/kg b.w., 6 days; oral) against acute Cadmium (Cd) (6.3 mg/kg b.w., single dose; oral) toxicity was evaluated in rats. Protective effect was assessed using serum markers, tissue antioxidants, oxidant derivatives, glycoprotein, and histopathological studies. The activities of serum marker enzymes were increased (40-60 %); antioxidant enzymes such as SOD and CAT, GSH, and its metabolic enzyme activities were decreased (50-80 %) in the liver and kidney upon Cd intoxication. During STAe pre-treatment, at doses of 250 and 500 mg/kg b.w., the above changes were brought to near normal (25-63 %). Tissue 4-hydroxynonenal, 3-nitrotyrosine, and protein carbonyls were increased (8-15 fold) in Cd-alone-treated rats, whereas pre-supplementation of STAe significantly decreased their levels and inhibited the protein glycosylation effectively. The pharmacological effect of STAe was confirmed by histopathological observations. Based on previous literature and present investigation, we conclude that ST may serve as a potential functional food against environmental contaminant such as heavy metal-induced oxidative stress.

In vitro anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit

The present study was undertaken to investigate the anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit and to explore the molecular mechanisms of action in MCF-7 cells. Cytotoxic properties of hexane, ethyl acetate and methanol extracts were carried out against MCF-7 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Ethyl acetate extract showed good cytototoxic activities compared to hexane and methanol extracts. Methyl caffeate was isolated from the ethyl acetate extract using column chromatography. Cytotoxic properties of methyl caffeate was investigated against MCF-7, A549, COLO320, HepG-2 and Vero cells. The compound showed potent cytotoxic properties against MCF-7 cells compared to A549, COLO320 and HepG-2 cells. Methyl caffeate significantly reduced cell proliferation and increased formation of fragmented DNA and apoptotic body in MCF-7 cells. Bcl-2, Bax, Bid, p53, caspase-3, PARP and cytochrome c release were detected by western blot analysis. The activities of caspases-3 and PARP gradually increased after the addition of isolated compound. Bcl-2 protein was down regulated; Bid and Bax were up regulated after the treatment with methyl caffeate. Molecular docking studies showed that the compound bound stably to the active sites of poly (ADP-ribose) polymerase-1 (PARP1), B cell CLL/lymphoma-2 (BCL-2), E3 ubiquitin-protein ligase (MDM2) and tubulin. The results strongly suggested that methyl caffeate induced apoptosis in MCF-7 cells via caspase activation through cytochrome c release from mitochondria.

α-Amylase inhibitory triterpene from Abrus precatorius leaves

In the screening experiments for porcine pancreatic α-amylase inhibitors in 18 plants obtained from Indonesia, a potent inhibitory activity was detected in the extract of leaves of Abrus precatorius. The enzyme assay-guided fractionation of the extract led to the isolation of a triterpene ketone, lupenone (1), as a potent α-amylase inhibitor, together with 24-methylenecycloartenone (2) and luteolin (3). The mode of inhibition of compound 1 against porcine pancreatic α-amylase was a mixed inhibition. This is the first report that describes the potent α-amylase inhibitory activity of the low-polar triterpene ketone similar to compound 1. A comparison of the activities of the isolate and related compounds indicated the importance of C-3 ketone and the lupane skeleton in the α-amylase inhibitory activity.

Advance in dietary polyphenols as α-glucosidases inhibitors: a review on structure-activity relationship aspect

The dietary polyphenols as α-glucosidases inhibitors have attracted great interest among researchers. The aim of this review is to give an overview of the research reports on the structure-activity relationship of dietary polyphenols inhibiting α-glucosidases. The molecular structures that influence the inhibition are the following: (1) The hydroxylation and galloylation of flavonoids including catechins improve the inhibitory activity. (2) The glycosylation of hyroxyl group and hydrogenation of the C2=C3 double bond on flavonoids weaken the inhibition. (3) However, cyaniding glycosides show higher inhibition against than cyanidin. Proanthocyanidins oligomers exhibit a stronger inhibitory activity than their polymers. (4) The hydroxylation on B ring and the glycosylation of stilbenes reduce the inhibitory activity. (5) Caffeoylquinic acids display strong inhibition against α-glucosidases. However, hydroxycinnamic acid, ferulic acid, and gallic acid hardly inhibited α-glucosidases. (6) The coupled galloyl structures attached to C-3 and C-6 of the 4C(1) glucose core of ellagitanin gave basic inhibitory activity. (7) The mono-glycosylation of chalcones slightly lowers the inhibition. However, the diglycosylation of chalcones significantly decreased the activity.

Antimicrobial and Antimycobacterial Activities of Methyl Caffeate Isolated from Solanum torvum Swartz. Fruit

ABSTRACT

Solanum torvum Swartz. (Solanaceae) fruit is traditionally used for the treatment of bacterial and fungal infections. The methanolic extract was subjected to activity guided fractionation by column chromatography over silica gel. The structure of the compound was elucidated using physical and spectroscopic data. The antimicrobial activity was screened using five Gram-positive bacteria, six Gram-negative bacteria, seven clinical isolates and four fungi. Antimycobacterial activity was screened against two Mycobacterium strains. The zone of inhibition by methyl caffeate ranged from 0 to 22 mm. The lowest minimum inhibitory concentration (MIC) values of methyl caffeate were: 50 μg/ml against P. vulgaris, 25 μg/ml against K. pneumoniae (ESBL-3971), 8 μg/ml against M. tuberculosis (H(37)Rv) and 8 μg/ml against M. tuberculosis (Rif(R)). Methyl caffeate showed moderate antimicrobial and prominent antimycobacterial activities. Methyl caffeate can be evaluated further for drug development.

Antihyperglycemic activity and antidiabetic effect of methyl caffeate isolated from Solanum torvum Swartz. fruit in streptozotocin induced diabetic rats

Natural remedies from medicinal plants are considered to be effective and safe alternatives to treat diabetes mellitus. Solanum torvum Swartz. fruit is widely used in the traditional system of medicine to treat diabetes. In the present study methyl caffeate, isolated from S. torvum fruit, was screened for its efficacy in controlling diabetes in animal models. Antihyperglycemic effect of methyl caffeate was studied in normal glucose-fed rats. The effects of oral administration of methyl caffeate (10, 20 and 40 mg/kg) for 28 days on body weight, fasting blood glucose, plasma insulin, hemoglobin, glycated hemoglobin, total protein, hepatic glycogen and carbohydrate metabolism enzymes in streptozotocin induced diabetic rats were investigated. Histological observations in the pancreas and GLUT4 expression in skeletal muscles were also studied. Methyl caffeate at 40 mg/kg significantly prevented the increase in blood glucose level after glucose administration at 60 min in comparison to the hyperglycemic control group. In streptozotocin induced diabetic rats, methyl caffeate produced significant reduction in blood glucose and increased body weight. The levels and/or activities of other biochemical parameters were near normal due to treatment with methyl caffeate. Methyl caffeate treated diabetic rats showed upregulation of GLUT4 and regeneration of β-cells in the pancreas. These results substantiated that methyl caffeate possessed hypoglycemic effect, and it could be developed into a potent oral antidiabetic drug.