Anti-Alzheimer's disease potential of coumarins from Angelica decursiva and Artemisia capillaris and structure-activity analysis

Objective: To use structure-activity analysis to study the anti-Alzheimer's disease(anti-AD) activity of natural coumarins isolated from Angelica decursiva and Artemisia capillaries, along with one purchased coumarin(daphnetin). Methods: Umbelliferone, umbelliferone 6-carboxylic acid, scopoletin, isoscopoletin, 7-methoxy coumarin, scoparone, scopolin, and esculetin have been previously isolated; however 2'-isopropyl psoralene was isolated from Angelica decursiva for the first time to evaluate their inhibitory effects against acetylcholinesterase(ACh E), butyrylcholinesterase(BCh E), and β-site amyloid precursor protein cleaving enzyme 1(BACE1) enzyme activity. We scrutinized the potentials of coumarins as cholinesterase and BACE1 inhibitors via enzyme kinetics and molecular docking simulation. Results: Among the test compounds, umbelliferone 6-carboxylic acid, esculetin and daphnetin exhibited potent inhibitory activity against ACh E, BCh E and BACE1. Both esculetin and daphnetin have a catechol group and exhibit significant anti-AD activity against ACh E and BCh E. In contrast, presence of a sugar moiety and methoxylation markedly reduced the anti-AD activity of the coumarins investigated in this study. With respect to BACE1 inhibition, umbelliferone 6-carboxylic acid, esculetin and daphnetin contained carboxyl or catechol groups, which significantly contributed to their antiAD activities. To further investigate these results, we generated a 3D structure of BACE1 using Autodock 4.2 and simulated binding of umbelliferone 6-carboxylic acid, esculetin and daphnetin. Docking simulations showed that different residues of BACE1 interacted with hydroxyl and carboxylic groups, and the binding energies of umbelliferone 6-carboxylic acid, esculetin and daphnetin were negative(-4.58,-6.25 and-6.37 kcal/mol respectively). Conclusions: Taken together, our results suggest that umbelliferone 6-carboxylic acid, esculetin and daphnetin have anti-AD effects by inhibiting ACh E, BCh E and BACE1, which might be useful against AD.

Inhibition of advanced glycation endproducts formation by Korean thistle,Cirsium maackii

Objective:To evaluate inhibitoy potential of seven Korean thistles against the advanced glyeatinn endproducts(AGE) formation as well as to identify responsible compounds from the most active species.Methods:We used an in vitro AGE inhibition assay to evaluate the antidiabetic complication potential of the methanol extracts of the selected Korean thistles.Results:Among the seven Korean thistles,the leaves of Cirsium maackii(C.maackii) exhibited the most significant inhibitory activity against AGE formation.By means of bioassay-directed fractionation,a lignan.chlorogenic acid and 14 flavonoids were isolated from the active ethyl acetate soluble fraction of a methanol extract from C.maackii leaves.Luteolin and its 5-O-glueoside have been previously isolated:however,a lignan and 13 known compounds were isolated for the first lime from C maackii leaves in this study.Most of the isolated compounds exhibited inhibitory activities against potential AGE formation.Among them,cernuoside was shown to be the most potent AGE inhibitor with an IC_(50) value of 21.21 μ mol/L.Most importantly,two major flavonoids,luteolin and ils 5-O-glucoside,also significantly inhibited AGE formation,with IC_(50) values of36.33 and 37.47 μmol/L,respectively.Structure activity relationship revealed that the presence of free 3'and 4' dihydroxyl group in flavonoids skeleton played an important role in AGE inhibition.Conclusions:These results indicate that C.maackii and C maackii-derived flavonoids might be explored further to develop therapeutic agents for the prevention of diabetic eoniplicalions due to their significant inhibitory activity against AGE formation.

Identification and quantification of flavonoids in Carica papaya leaf and peroxynitrite-scavenging activity

Objective: To characterize the types, contents, and peroxynitrite-scavenging activities of flavonoids in the leaf of Carica papaya(C. papaya).Methods: Chromatographic and spectroscopic techniques along with high performance liquid chromatography quantitative analysis and peroxynitrite-scavenging assay were performed to isolate and quantify flavonoid compounds in the flavonoid-rich fraction(Bu OH fraction) derived from Me OH extract of C. papaya leaves and evaluate their peroxynitrite-scavenging activities.Results: Seven flavonoids were isolated from the leaves of C. papaya, including quercetin 3-(2~G-rhamnosylrutinoside), kaempferol 3-(2~G-rhamnosylrutinoside), quercetin 3-rutinoside, myricetin 3-rhamnoside, kaempferol 3-rutinoside, quercetin, and kaempferol. All of the substances exhibited potent activities on peroxynitrite scavenging(IC50 4.15 mmol/L), which were stronger than the positive control, L-penicillamine(6.90 mmol/L). The content of kaempferol 3-(2~G-rhamnosylrutinoside) was significantly higher than other identified compounds(123.18 mg/g Bu OH fraction and 7.23 mg/g Me OH extract).Conclusions: The results of the present study demonstrate the potent antioxidant flavonoids of C. papaya leaf, with kaempferol 3-(2~G-rhamnosylrutinoside) as the major one.

Anti-acetylcholinesterase activity of the aglycones of phenolic glycosides isolated from Leonurus japonicus

Objective: To find the genuine structure with anti-acetylcholinesterase(anti-ACh E) from the phenolic glycosides abundant in Leonurus japonicus(Lamiaceae). The assay for antiACh E activity is often used to lead anti-Alzheimer's drugs.Methods: The five phenolic glycosides, tiliroside, leonurusoside C, 2’’’-syringoylrutin,rutin, and lavanduliofolioside were isolated from L. japonicus. The activities of the glycosides were relatively low. Seven compounds including p-coumaric acid, caffeic acid, hydroxytyrosol, salidroside, syringic acid, kaempferol, and quercetin, which are produced by the hydrolysis of the five glycosides, were also assayed for anti-ACh E activity.Results: Of those seven compounds, the five compounds other than salidroside and syringic acid exhibited potent anti-ACh E activities. In particular, the IC_(50)s of caffeic acid and quercetin were(1.05 ± 0.19) and(3.58 ± 0.02) mg/m L, respectively. Rutin was the most abundant flavonoid in the extract(9.18 mg/g as measured by HPLC).Conclusion: The substances with potent anti-ACh E were caffeic acid, quercetin, pcoumaric acid, kaempferol, and hydroxytyrosol that can be produced from their glycosides.

Comparative molecular docking studies of lupeol and lupenone isolated from Pueraria lobata that inhibits BACE1: Probable remedies for Alzheimer's disease

Objective: To discover lead lupane triterpenoid's potential isolated from Pueraria lobata roots against b-site amyloid precursor protein cleaving enzyme 1(BACE1), which serve as a rate limiting step in amyloid beta(Aβ) production altering the course of Alzheimer's disease. In addition, enzyme kinetics study and molecular docking were conducted to establish the inhibition type and structure activity relationship.Methods: A systematic study of 70% ethanolic P. lobata root extract was employed to identify its BACE1 inhibitory potential. Further, BACE1 inhibitory potential of two lupane terpenoids, yielded from ethanolic extract, was assessed. In order to determine their inhibition mode, Lineweaver–Burk plots and Michaelis–Menten model for BACE1 was performed. Auto Dock 4.2 program in addition determined the molecular interaction of BACE1 with isolated terpenoids.Results: Considering the inhibitory potential of 70% ethanolic extract of P. lobata against BACE1(IC_(50)= 80.35 mg/mL), lupeol and lupenone were subsequently isolated and exhibited notable or moderate BACE1 inhibitory activity with IC_(50) values of 5.12 and 62.98 mmol/L, respectively, as compared to the positive control quercetin(IC_(50)= 21.28 mmol/L). The enzyme kinetics study enabled us to identify both compounds as competitive inhibitors, where lupeol displayed a very potent inhibition against BACE1 with low inhibition constant(Ki) value of 1.43 mmol/L, signifying greater binding affinity.In order to understand the binding mechanism and structure–activity relationship of two triterpene-based BACE1 inhibitors, we employed computer aided docking studies which evidently revealed that hydroxyl group of lupeol formed two hydrogen bonds with the ASP32(catalytic aspartic residue) and SER35 residues of BACE1 with the binding energy of(-8.2 kcal/mol), while the ketone group of lupenone did not form any hydrogen bonds with BACE1 giving evidence for less binding affinity. These results in turn have predicted the dependence of the inhibitory activity in the presence of hydroxyl group which has provided a new basis for BACE1 blockade.Conclusions: Our results have successfully explored the molecular mechanism of lupane triterpenoids via BACE1 inhibition, suggesting that lupeol in particular could be utilized as a useful therapeutic and preventive agent to mitigate Alzheimer's disease.

Chinese Prescription Kangen-karyu as Potential Anti-Alzheimer’s Disease Therapeutic:Analyses of BACE1 and GSK-3βInhibitory Activities

Inhibition ofβ-site amyloid precursor protein-cleaving enzyme 1(BACE1)or glycogen synthase kinase-3β(GSK-3β)is estimated to be the central therapeutic approach for Alzheimer’s disease(AD).In this study,water extract of Kangenkaryu,its crude drug and chemical composition used in oriental medicine were evaluated regarding their BACE1 and GSK-3βinhibitory activities.Fluorescence resonance energy transfer was used to characterize the BACE1 inhibitory effect of Kangen-karyu,its crude drug and chemical composition.GSK-3βactivity was determined using the Kinase-Glo Luminescent Kinase Assay Platform.The water extract of Kangen-karyu inhibited BACE1 and GSK-3βin concentration-dependent manners when compared with reference drugs,quercetin and luteolin.Among six components of Kangen-karyu,the water extracts of Salviae Miltiorrhizae Radix or Cyperi Rhizoma exhibited significant inhibitory effects on BACE1 and GSK-3β.Among the constituents of Salviae Miltiorrhizae Radix extract,salvianolic acid C,salvianolic acid A,rosmarinic acid,and magnesium lithospermate B significantly inhibited BACE1.In addition,they inhibited GSK-3βwith an IC50 value range of 6.97 to 135.35μM.From these results,one of the effectiveness and its mechanisms of action of Kangen-karyu against AD may be the inhibition of BACE1 and GSK-3β,and one of the active ingredients of Kangen-karyu is Salviae Miltiorrhizae Radix and its constituents.