Automating a 96-well microtiter plate assay for identification of AGEs inhibitors or inducers: application to the screening of a small natural compounds library

Looking for Actives in the Haystack: Merging HRMS2-Based Molecular Networking, Chemometrics, and 13C NMR-Based Dereplication Approaches

The identification of bioactive natural products (NPs) in complex mixtures has become an important subject of contemporary NP research. In an attempt to address this challenge, the present work proposes an integrated strategy that combines tandem mass spectrometry (MS2)-based molecular networking (MN), a partial least-squares (PLS) chemometric model, as well as 13C NMR-based dereplication using MixONat software. In addition, an advanced glycation end product (AGEs) assay was used for activity evaluation. The approach was implemented on a Garcinia parvifolia bark extract that comprised a high content of prenylated xanthones and had previously shown a notable inhibitory effect on AGE formation. As a main result, the proposed strategy permitted the identification of potentially active metabolites within complex mixtures and their annotation with a higher level of confidence by NMR data. Overall, this comprehensive approach provides a powerful and efficient solution for the targeting and annotating of active compounds in complex NP mixtures.

LC-MS Profiling of Kakkonto and Identification of Ephedrine as a Key Component for Its Anti-Glycation Activity

A total of 147 oral Kampo prescriptions, which are used clinically in Japan, were evaluated for their anti-glycation activity. Kakkonto demonstrated significant anti-glycation activity, prompting further analysis of its chemical constituents using LC-MS, which revealed the presence of two alkaloids, fourteen flavonoids, two but-2-enolides, five monoterpenoids, and four triterpenoid glycosides. To identify the components responsible for its anti-glycation activity, the Kakkonto extract was reacted with glyceraldehyde (GA) or methylglyoxal (MGO) and analyzed using LC-MS. In LC-MS analysis of Kakkonto reacted with GA, the peak intensity of ephedrine was attenuated, and three products from ephedrine-scavenging GA were detected. Similarly, LC-MS analysis of Kakkonto reacted with MGO revealed two products from ephedrine reacting with MGO. These results indicated that ephedrine was responsible for the observed anti-glycation activity of Kakkonto. Ephedrae herba extract, which contains ephedrine, also showed strong anti-glycation activity, further supporting ephedrine's contribution to Kakkonto's reactive carbonyl species' scavenging ability and anti-glycation activity.

GC-MS and LC-DAD-MS Phytochemical Profiling for Characterization of Three Native Salvia Taxa from Eastern Mediterranean with Antiglycation Properties

Salvia fruticosa and S. pomifera subsp. calycina are native to Eastern Mediterranean and S. pomifera subsp. pomifera is endemic to Greece. The primary aim of this study was to develop an analytical methodology for metabolomic profiling and to study their efficacy in combating glycation, the major biochemical complication of diabetes. After sequential ultrasound-assisted extraction of 2 g of leaves with petroleum ether and 70% methanol, the volatile metabolites in the petroleum ether extracts were studied with GC-MS (Gas Chromatography-Mass Spectrometry), whereas the polar metabolites in the hydroalcoholic extracts were determined and quantified by UHPLC-DAD-ESI-MS (Ultra-High Performance Liquid Chromatography-Diode Array Detector-Mass Spectrometry). This methodology was applied to five populations belonging to the three native taxa. 1,8-Cineole was the predominant volatile (34.8-39.0%) in S. fruticosa, while S. pomifera had a greater content of α-thujone (19.7-41.0%) and β-thujone (6.0-39.1%). Principal Component Analysis (PCA) analysis of the volatiles could discriminate the different taxa. UHPLC-DAD-ESI-MS demonstrated the presence of 50 compounds, twenty of which were quantified. PCA revealed that not only the taxa but also the populations of S. pomifera subsp. pomifera could be differentiated. All Salvia samples inhibited advanced glycation end-product formation in a bovine serum albumin/2-deoxyribose assay; rosmarinic and carnosic acid shared this activity. This study demonstrates the antiglycation activity of S. fruticosa and S. pomifera extracts for the first time and presents a miniaturized methodology for their metabolomic profiling, which could aid chemotaxonomic studies and serve as a tool for their authentication and quality control.

Natural Products as a Source of Inspiration for Novel Inhibitors of Advanced Glycation Endproducts (AGEs) Formation

Protein glycation, a post-translational modification found in biological systems, is often associated with a core defect in glucose metabolism. In particular, advanced glycation endproducts are complex heterogeneous sugar-derived protein modifications implicated in the progression of pathological conditions such as atherosclerosis, diabetic complications, skin diseases, rheumatism, hypertension, and neurodegenerative diseases. Undoubtedly, there is the need to expand the knowledge about antiglycation agents that can offer a therapeutic approach in preventing and treating health issues of high social and economic importance. Although various compounds have been under consideration, little data from clinical trials are available, and there is a lack of approved and registered antiglycation agents. Next to the search for novel synthetic advanced glycation endproduct inhibitors, more and more the efforts of scientists are focusing on researching antiglycation compounds from natural origin. The main purpose of this review is to provide a thorough overview of the state of scientific knowledge in the field of natural products from plant origin (e.g., extracts and pure compounds) as inhibitors of advanced glycation endproduct formation in the period between 1990 and 2019. Moreover, the objectives of the summary also include basic chemistry of AGEs formation and classification, pathophysiological significance of AGEs, mechanisms for inhibiting AGEs formation, and examples of several synthetic anti-AGEs drugs.

In Vitro Antioxidant and Anti-Glycation Activity of Resveratrol and Its Novel Triester with Trolox

Resveratrol (RSV) is well known for its many beneficial activities, but its unfavorable physicochemical properties impair its effectiveness after systemic and topical administration; thus, several strategies have been investigated to improve RSV efficacy. With this aim, in this work, we synthesized a novel RSV triester with trolox, an analogue of vitamin E with strong antioxidant activity. The new RSV derivative (RSVTR) was assayed in vitro to evaluate its antioxidant and anti-glycation activity compared to RSV. RSVTR chemical stability was assessed at pH 2.0, 6.8, and 7.2 and different storage temperatures (5 °C, 22 °C, and 37 °C). An influence of pH stronger than that of temperature on RSVTR half-life values was pointed out, and RSVTR greatest stability was observed at pH 7.2 and 5 °C. RSVTR showed a lower antioxidant ability compared to RSV (determined by the oxygen radical absorbance capacity assay) while its anti-glycation activity (evaluated using the Maillard reaction) was significantly greater than that of RSV. The improved ability to inhibit the glycation process was attributed to a better interaction of RSVTR with albumin owing to its increased topological polar surface area value and H-bond acceptor number compared to RSV. Therefore, RSVTR could be regarded as a promising anti-glycation agent worthy of further investigations.

Carob Seeds: Food Waste or Source of Bioactive Compounds?

(1) Background: For centuries, carob fruit has been used in the food field, while carob seeds have been mainly considered as food waste. Nowadays, there has been considerable attention toward the recovery of the waste plant matrices as possible sources of functional compounds with health properties. Therefore, our goal was to evaluate the health properties of carob seed extracts, and to study the effects of the ripening process on the chemical composition of the extracts. (2) Methods: After the mechanical separation of seeds from carob fruit, an ultrasound-assisted extraction (UAE) was performed to maximize and preserve the quality of bioactive compounds. Seed extracts were characterized by high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) for the content of bioactive polyphenols, and were finally analyzed by oxygen radical absorbance capacity (ORAC), NO Scavenger (NO) and advanced glyoxidation end products (AGEs) assays, in order to estimate the antioxidant potential of the active compounds. (3) Results: Although both seed extracts of carob unripe (CAR-UR) and ripe (CAR-R) showed an interesting antioxidant activity, CAR-R had greater activity due to the procyanidins content. (4) Conclusions: Based on the obtained results, carob seed extracts could be regarded as interesting source of bioactive antioxidant compounds for a potential application in nutraceutical and food supplement fields.

Natural Flavones and Flavonols: Relationships among Antioxidant Activity, Glycation, and Metalloproteinase Inhibition

Reactive oxygen and nitrogen species as well as advanced glycation endproducts (AGEs) and metalloproteinases (MMPs) play a key role in the development and progression of degenerative processes of body tissues, including skin. Natural antioxidant flavonoids could be beneficial in inhibiting AGEs’ formation and MMPs’ expression. In this study, the antioxidant activity of flavones (luteolin, apigenin, and chrysin) and flavonols (mirycetin, quercetin, and kaempferol) was compared with their inhibitory effects on both metalloproteinases’ (MMP-1, MMP-2, MMP-9, MMP-13) and AGEs’ formation. Comparisons were performed taking into account the hydroxyl group arrangement and the physico-chemical parameters the binding dissociation enthalpy (BDE), ionization potential (IP), partition coefficient (log P), and topological polar surface area (TPSA). Increasing the number of hydroxyl groups led to a proportional enhancement of antioxidant activity while an inverse relationship was observed plotting the antioxidant activity vs. BDE and IP values. All flavonoids acted as AGEs, MMP-1, and MMP-13 inhibitors, but they were less effective against MMP-2 and MMP-9. The inhibition of MMP-1 seemed to be related to the TPSA values while high TPSA and low log P values seemed important conditions for inhibiting MMP-13. Overall, our data suggest that an estimation of flavonoid activity could be anticipated based on their physico-chemical parameters.

Interaction of chlorpropamide with serum albumin: Effect on advanced glycated end (AGE) product fluorescence

Carrier proteins like bovine or human serum albumin (BSA and HSA, respectively) are prone to glycation as compared to the other available proteins. In this study, reducing sugars such as l-arabinose (ara), d-(-) galactose (gal) and d-(-) fructose (fru) were used to create model glycated serum albumins and binding ability of these with well-known antidiabetic drug chlorpropamide (CPM) was monitored. Fluorescence quenching experiment revealed that interaction of CPM with native as well as glycated albumins undergoes through a ground state complex formation. CPM binds strongly to glycated HSA with arabinose (gHSA_ara) as compared to other glycated systems and to the native proteins. CPM interacts through Van der Waals and hydrogen bonding interaction to glycated BSA by d-(-) fructose (gBSA_fru) and also with native HSA; whereas, it's interaction with BSA and others glycated systems like gBSA_ara, gBSA_gal and gHSA_ara occurs primarily through hydrophobic interaction. CPM showed an enhancement in the production of the advanced glycated end products (AGE) in all the glycated proteins. The difference in the binding capability of CPM to differently glycated albumins could be a major model to understand the drug carrying capacity of the glycated serum albumins.

Solid Lipid Nanoparticles Loading Idebenone Ester with Pyroglutamic Acid: In Vitro Antioxidant Activity and In Vivo Topical Efficacy

Idebenone (IDE), a strong antioxidant widely investigated for the treatment of neurodegenerative diseases and skin disorders, shows low oral and topical bioavailability due to its unfavorable physico-chemical properties. In this work, to improve IDE topical effectiveness, we explored a two-steps approach: (1) we synthesized an IDE ester (IDEPCA) with pyroglutamic acid, a molecule whose hydrating effects are well known; (2) we loaded IDEPCA into solid lipid nanocarriers (SLN). We evaluated in vitro antioxidant and anti-glycation activity and in vivo hydrating effects after topical application in human volunteers from gel vehicles of IDEPCA SLN in comparison to IDE SLN. All SLN showed good technological properties (mean particle size < 25 nm, polydispersity index < 0.300, good stability). The oxygen radical absorbance capacity assay showed that IDEPCA SLN and IDE SLN had similar antioxidant activity while IDEPCA SLN were more effective in the in vitro NO scavenging assay. Both IDEPCA and IDE SLN showed the same effectiveness in inhibiting the formation of advanced glycation end products. In vivo experiments pointed out a better hydrating effect of IDEPCA SLN in comparison to IDE SLN. These results suggest that the investigated approach could be a promising strategy to obtain topical formulations with increased hydrating effects.

Secondary metabolites from lichen as potent inhibitors of advanced glycation end products and vasodilative agents

Secondary metabolites from lichens are known for exhibiting various biological effects such as anti-inflammatory, antioxidant and antibacterial activities. Despite this wide range of reported biological effects, their impact on the formation of advanced glycation end products (AGEs) remains vastly unexplored. The latter are known contributors to lifestyle and age-related diseases such as Alzheimer and Parkinson. Moreover, the development of atherosclerosis and arterial stiffness is causally linked to the formation of AGEs. With this in mind, the present work evaluated the inhibitory effects of secondary lichen metabolites on the formation of pentosidine-like AGEs' by using an in vitro, Maillard reaction based, fluorescence assay. Overall, thirty-seven natural and five synthetically modified compounds were tested, eighteen of which exhibiting IC₅₀ values in the range of 0.05 to 0.70 mM. This corresponds to 2 to 32 fold of the inhibitory activity of aminoguanidine. Targeting one major inhibiting mechanism of AGEs formation, all compounds were additionally evaluated on their radical scavenging capacities in an DPPH assay. Furthermore, as both AGEs' formation and hypertension are major risk factors for atherosclerosis, compounds that were available in sufficient amounts were also tested for their vasodilative effects. Overall, and though some of the active compounds were previously reported cytotoxic, present results highlight the interesting potential of secondary lichen metabolites as anti-AGEs and vasodilative agents.

Synthesis and biological evaluation of stilbene derivatives coupled to NO donors as potential antidiabetic agents

The work is focused on the design of drugs that prevent and treat diabetes and its complications. A novel class of stilbene derivatives were prepared by coupling NO donors of alkyl nitrate and were fully characterised by NMR and other techniques. These compounds were tested in vitro activity, including α-glucosidase inhibitory activity, aldose reductase (AR) inhibitory activity and advanced glycation end products (AGEs) formation inhibitory activity. A class of modified compounds could play a significant effect for treatment of diabetic complications. Target compounds 3e and 7c offered a potential drug design concept for the development of therapeutic or preventive agents for diabetes and its complications.

An Alginate/Cyclodextrin Spray Drying Matrix to Improve Shelf Life and Antioxidant Efficiency of a Blood Orange By-Product Extract Rich in Polyphenols: MMPs Inhibition and Antiglycation Activity in Dysmetabolic Diseases

Alginate and β-cyclodextrin were used to produce easily dosable and spray-dried microsystems of a dried blood orange extract with antidysmetabolic properties, obtained from a by-product fluid extract. The spray-dried applied conditions were able to obtain a concentrate dried extract without the loss of AOA and with TPC and TMA values of 35–40% higher than that of the starting material. They were also effective in producing microparticles with 80–100% of encapsulation efficiency. The 2% sodium alginate was capable of improving the extract shelf life, while the beta-cyclodextrin (1 : 1 molar ratio with dried extract) prolonged the extract antioxidant efficiency by 6 hours. The good inhibition effect of the dried extract on the AGE formation and the MMP-2 and MMP-9 activity is presumably due to a synergic effect exerted by both anthocyanin and bioflavonoid extract compounds and was improved by the use of alginate and cyclodextrin.

Development and In Vitro Evaluation of an Innovative "Dietary Flavonoid Supplement" on Osteoarthritis Process

The aim of this study was to evaluate the antidegenerative effect in osteoarthritis damage of eriocitrin alone and eriocitrin formulated as innovative "dietary flavonoid supplement." A complexation between eriocitrin and hydroxypropyl β-cyclodextrin by solubilization/freeze-drying method was performed. The complex in solution was evaluated by phase solubility studies and the optimal 1 : 2 flavanone/cyclodextrin molar ratio was selected. Hydroxypropyl β-cyclodextrin was able to complex eriocitrin as confirmed by UV-Vis absorption, DSC, and FTIR studies. The complex formed increased the eriocitrin water solubility (from 4.1 ± 0.2 g·L-1 to 11.0 ± 0.1 g·L-1) and dissolution rate (from 37.0% to 100%) in 30 min. The in vitro studies exhibit the notion that eriocitrin and its complex inhibit AGEs in a similar manner because hydroxypropyl β-cyclodextrin does not interfere with the flavanone intrinsic property. Instead, the presence of cyclodextrin improves eriocitrin antioxidant stability maintaining a high fluorescence value until 8 hours with respect to the pure materials. Moreover, hydroxypropyl β-cyclodextrin showed moderate GAGs restoration acting synergistically with the complexed compound to maintain the structural chondrocytes integrity. The results point out that ERT/HP-betaCD complex possesses technological and biological characteristics able to obtain an easily soluble nutraceutical product, which reduces the degenerative and oxidative damage which occurs in osteoarthritis, and improve the patient compliance.

Anti-Advanced Glycation End-product and Free Radical Scavenging Activity of Plants from the Yucatecan Flora

Background:

Formation and accumulation of advanced glycation end-products (AGE) is recognized as a major pathogenic process in diabetic complications, atherosclerosis and cardiovascular diseases. In addition, reactive oxygen species and free radicals have also been reported to participate in AGE formation and in cell damage. Natural products with antioxidant and antiAGE activity have great therapeutic potential in the treatment of diabetes, hypertension and related complications. Objective: to test ethanolic extracts and aqueous-traditional preparations of plants used to treat diabetes, hypertension and obesity in Yucatecan traditional medicine for their anti-AGE and free radical scavenging activities.

Materials and Methods:

ethanolic extracts of leaves, stems and roots of nine medicinal plants, together with their traditional preparations, were prepared and tested for their anti-AGE and antioxidant activities using the inhibition of advanced glycation end products and DPPH radical scavenging assays, respectively.

Results:

the root extract of C. fistula (IC₅₀= 0.1 mg/mL) and the leaf extract of P. auritum (IC₅₀= 0.35 mg/mL) presented significant activity against vesperlysine and pentosidine-like AGE. Although none of the aqueous traditional preparations showed significant activity in the anti-AGE assay, both the traditional preparations and the ethanolic extracts of E. tinifolia, M. zapota, O. campechianum and P. auritum showed significant activity in the DPPH reduction assay.

Conclusions:

the results suggest that the metabolites responsible for the detected radical-scavenging activity are different to those involved in inhibiting AGE formation; however, the extracts with antioxidant activity may contain other metabolites which are able to prevent AGE formation through a different mechanism.

SUMMARY

Ethanolic extracts from nine plants used to treat diabetes, hypertension and obesity in Yucatecan traditional medicine were tested for their anti-AGE and free radical scavenging activities.

Significant activity against vesperlysine and pentosidine-like AGE was detected in the root extract of Cassia fistula and the leaf extract of Piper auritum.

Traditional preparations and the ethanolic extracts of Ehretia tinifolia, Manilkara zapota, Ocimum campechianum and Piper auritum showed significant activity in the DPPH reduction assay.

Results suggest that the metabolites responsible for the detected radical-scavenging activity are different to those involved in inhibiting AGE formation.

Abbreviations Used: AGE: Advanced glycation end-product; DPPH: 2,2-Diphenyl-1-picrylhydrazyl; DM: Diabetes mellitus; ROS: Reactive oxygen species; BSA: Bovine serum albumin; EtOH: Ethanol; EtOAc: Ethyl acetate; ANOVA: Analysis of variance; BA: Brosimum alicastrum; BS: Bunchosia swartziana; CF: Cassia fistula; CN: Cocos nucifera; ET: Ehretia tinifolia; MZ: Manilkara zapota; OC: Ocimum campechianum; PA: Piper auritum; RM: Rhizophora mangle; L: Leaves; S: Stems; R: Roots; T: traditional preparation; I: Inflorescences; W: Water

Antidiabetic property of Aerva lanata (L.) Juss. ex Schult. is mediated by inhibition of alpha glucosidase, protein glycation and stimulation of adipogenesis

BACKGROUND

Diabetes is the leading cause of morbidity and mortality, with a number currently diagnosed as high as 371 million. Plant-based therapy could be an ideal choice because of fewer side-effects and wider acceptability. Hence, the antihyperglycemic potential of Aerva lanata, a herb prescribed for diabetes in Ayurveda was evaluated to elucidate its possible mechanism of action.

METHODS

High performance liquid chromatography analysis was used for the characterization of 70% ethanolic (aqueous leaf extract [ALE]) and ethyl acetate (AEA) extracts. Further, they were evaluated for their antioxidant, inhibition of alpha glucosidase, protein glycation dipeptidyl peptidase IV (DPP IV), protein tyrosine phosphatase 1B (PTP1B) and stimulation of glucose uptake and glitazone like property (adipogenic potential) using in vitro models. The promising alpha glucosidase inhibitory potential of ALE was further evaluated in normal and streptozotocin (STZ) diabetic rats.

RESULTS

ALE inhibited yeast (IC50 - 81.76 μg/mL) and rat intestinal alpha glucosidase (IC50 - 108.7 μg/mL), protein glycation, DPP IV enzyme (IC50 - 118.62 μg/mL) and PTP1B (IC50 - 94.66 μg/mL). ALE stimulated maximal adipogenesis at 50 μg/mL and enhanced insulin mediated glucose uptake (threefold of basal) at 100 μg/mL in L6 myotubes. ALE (500 mg/kg b.w.) showed a significant antihyperglycemic activity in sucrose loaded STZ normal (15.57%) and diabetic (18.44%) rats. HPLC analysis of ALE revealed the presence of bioactives like alpha amyrin, betulin and beta sitosterol.

CONCLUSIONS

Alpha glucosidase inhibition, antiglycation, and adipogenic potential significantly contribute to the antidiabetic property of Aerva lanata. In addition, insulin sensitization and antioxidant potential also enhance its therapeutic potential.

An in vitro study reveals nutraceutical properties of Ananas comosus (L.) Merr. var. Mauritius fruit residue beneficial to diabetes

BACKGROUND

Rapid urbanisation and nutritional transition is fuelling the increased global incidence of type 2 diabetes. Pineapple fruit residue was explored for its nutraceutical properties as an alternative or adjunct to currently available treatment regime. Ethyl acetate and methanolic extracts of pineapple fruit residue were evaluated for anti-diabetic activity in cell free and cell based systems. Specifically, we assessed: (1) antioxidant potential, (2) anti-glycation potential, (3) carbohydrate digestive enzyme inhibition, and (4) lipid accumulation and glycerol-3-phosphate dehydrogenase activity in differentiating 3T3-L1 cells.

RESULTS

The active components in the ethyl acetate and methanolic extracts were identified as sinapic acid, daucosterol, 2-methylpropanoate, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, methyl 2-methylbutanoate and triterpenoid ergosterol using DART/HRMS and ESI/HRMS. Micronutrient analysis revealed the presence of magnesium, potassium and calcium. Adipogenic potential, anti-glycation property of the ethyl acetate extract, and DNA damage protection capacity of the methanolic extract are promising.

CONCLUSION

Results from this study clearly indicate that pineapple fruit residue could be utilised as a nutraceutical against diabetes and related complications.

Chemical composition, antioxidant and anti-AGEs activities of a French poplar type propolis

Accumulation in tissues and serum of advanced glycation end-products (AGEs) plays an important role in pathologies such as Alzheimer's disease or, in the event of complications of diabetes, atherosclerosis or renal failure. Therefore, there is a potential therapeutic interest in compounds able to lower intra and extracellular levels of AGEs. Among them, natural antioxidants (AO) with true anti-AGEs capabilities would represent good candidates for development. The purpose of this study was to evaluate the AO and anti-AGEs potential of a propolis batch and then to identify the main compounds responsible for these effects. In vivo, protein glycation and oxidative stress are closely related. Thus, AO and antiglycation activities were evaluated using both DPPH and ORAC assays, respectively, as well as a newly developed automated anti-AGEs test. Several propolis extracts exhibited very good AO and anti-AGEs activities, and a bioguided fractionation allowed us to identify pinobanksin-3-acetate as the most active component.

Tuning a 96-well microtiter plate fluorescence-based assay to identify AGE inhibitors in crude plant extracts

Advanced glycation end-products (AGEs) are involved in the pathogenesis of numerous diseases. Among them, cellular accumulation of AGEs contributes to vascular complications in diabetes. Besides using drugs to lower blood sugar, a balanced diet and the intake of herbal products potentially limiting AGE formation could be considered beneficial for patients’ health. The current paper presents a simple and cheap high-throughput screening (HTS) assay based on AGE fluorescence and suitable for plant extract screening. We have already implemented an HTS assay based on vesperlysines-like fluorescing AGEs quickly (24 h) formed from BSA and ribose under physiological conditions. However, interference was noted when fluorescent compounds and/or complex mixtures were tested. To overcome these problems and apply this HTS assay to plant extracts, we developed a technique for systematic quantification of both vesperlysines (λ_exc 370 nm; λ_em 440 nm) and pentosidine-like (λ_exc 335 nm; λ_em 385 nm) AGEs. In a batch of medicinal and food plant extracts, hits were selected as soon as fluorescence decreased under a fixed threshold for at least one wavelength. Hits revealed during this study appeared to contain well-known and powerful anti-AGE substances, thus demonstrating the suitability of this assay for screening crude extracts (0.1 mg/mL). Finally, quercetin was found to be a more powerful reference compound than aminoguanidine in such assay.

Synthesis and evaluation of naphthoic acid derivatives as fluorescent probes to screen advanced glycation end-products breakers

Advanced glycation end-products, namely AGEs, are involved in the pathogenesis of numerous diseases. If AGEs inhibitors are well-known, only few products are described as compounds able to destroy those deleterious products. In this work, we describe naphthoic acid derivatives, particularly 1-(naphthalen-1-yl)propane-1,2-dione 9, allowing the simple and rapid detection of AGEs breakers using a 96-well microplate fluorescence assay. Since the inaugurate publication about AGEs breakers whose activity was demonstrated using HPLC analysis, this work proposes the first assay suitable for automated and high throughput screening of AGEs breakers.

Bioguided fractionation and isolation of natural inhibitors of advanced glycation end-products (AGEs) from Calophyllum flavoramulum

Advanced glycation end-products (AGEs) are associated with many pathogenic disorders such as Alzheimer's disease, pathogenesis of diabetes, atherosclerosis or endothelial dysfunction leading to cardiovascular events. Clusiaceae and Calophyllaceae families are rich in compounds like polyphenols which are able to inhibit their formation and are therefore of great interest. Calophyllum flavoramulum Hend. & Wyatt-Sm., a native Malaysian plant, was selected after an anti-AGEs screening conducted on DCM and MeOH extracts from plants belonging to these aforementioned families. In a first study, bioguided fractionation of the MeOH leaf extract of C. flavoramulum afforded amentoflavone, 3-methoxy-2-hydroxyxanthone, 3,4-dihydroxy-tetrahydrofuran-3-carboxylic acid, quercitrin, 3,4-dihydroxybenzoic acid, canophyllol and apetalactone. Amentoflavone and 3-methoxy-2-hydroxyxanthone were found to be very potent (IC(50)=0.05 and 0.06 mM respectively), while anti-AGEs activities of quercitrin and 3,4-dihydroxybenzoic acid appeared as moderately strong (IC(50)=0.5 mM). In a second study, a systematic phytochemical study of the cyclohexane, DCM and EtOAc extracts obtained from the same plant was conducted to isolate the following products: flavoramulone, 6-deoxyjacareubin, rheediachromenoxanthone, 2,3-dihydroamentoflavone and benzoic acid. 3,4-Dihydroxy-tetrahydrofuran-3-carboxylic acid and flavoramulone were isolated for the first time and their structures were identified by means of IR, MS and NMR spectrometries.

Preparative isolation, fast centrifugal partition chromatography purification and biological activity of cajaflavanone from Derris ferruginea stems

INTRODUCTION

The Derris genus is known to contain flavonoid derivatives, including prenylated flavanones and isoflavonoids such as rotenoids, which are generally associated with significant biological activity.

OBJECTIVE

To develop an efficient preparative isolation procedure for bioactive cajaflavanone.

METHODOLOGY

Fast centrifugal partition chromatography (FCPC) was optimised to purify cajaflavanone from Derris ferruginea stems in a single step as compared to fractionation from the cyclohexane extract by successive conventional solid-liquid chromatography procedures. The purification yield, purity, time and solvent consumption per procedure are described. The anti-fungal, anti-bacterial, anti-leishmanial, anti-plasmodial, anti-oxidant activities and the inhibition of advanced glycation end-products (AGEs) by cajaflavanone accumulation are described.

RESULTS

FCPC enabled cajaflavanone purification in a single separation step, yielding sufficient quantities to perform in vitro biological screening. Interestingly, cajaflavanone had an inhibitory effect on the formation of AGEs, without displaying any in vitro anti-oxidant activity.

CONCLUSION

A simple and efficient procedure, in comparison with other preparative methods, for bioactive cajaflavone purification has been developed using FCPC.