Hee Jin Jung

Phlorotannins isolated from the edible brown alga Ecklonia stolonifera exert anti-adipogenic activity on 3T3-L1 adipocytes by downregulating C/EBPα and PPARγ

The dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism. Inhibition of adipocyte differentiation has been suggested to be an important strategy for preventing or treating obesity. In our previous study, we characterized an Ecklonia stolonifera extract and non-polar fractions thereof, including dichloromethane and ethyl acetate fractions. We showed that these fractions inhibited adipocyte differentiation and lipid formation/accumulation in 3T3-L1 preadipocytes, as assessed by Oil Red O staining. As part of our ongoing search for anti-obesity agents derived from E. stolonifera, in this work, we characterized five known phlorotannins, including phloroglucinol, eckol, dieckol, dioxinodehydroeckol, and phlorofucofuroeckol A, all of which were isolated from the active ethyl acetate fraction of E. stolonifera. We determined the chemical structures of these phlorotannins through comparisons of published nuclear magnetic resonance (NMR) spectral data. Furthermore, we screened these phlorotannins for their abilities to inhibit adipogenesis over a range of concentrations (12.5-100 μM). Of these five phlorotannins, phloroglucinol, eckol, and phlorofucofuroeckol A significantly concentration-dependently inhibited lipid accumulation in 3T3-L1 cells without affecting cell viability. In addition, the five isolated phlorotannins also significantly reduced the expression levels of several adipocyte marker genes, including proliferator activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα), although they did so to different extents. These results suggest that the molecular weight of a phlorotannin is an important factor affecting its ability to inhibit adipocyte differentiation and modulate the expression levels of adipocyte marker genes.

Inhibitory activities of major anthraquinones and other constituents from Cassia obtusifolia against β-secretase and cholinesterases.

ETHNOPHARMACOLOGICAL RELEVANCE Semen Cassiae has been traditionally used as an herbal remedy for liver, eye, and acute inflammatory diseases. Recent pharmacological reports have indicated that Cassiae semen has neuroprotective effects, attributable to its anti-inflammatory actions, in ischemic stroke and Alzheimers disease (AD) models. AIM OF THE STUDY The basic goal of this study was to evaluate the anti-AD activities of C. obtusifolia and its major constituents. Previously, the extract of C. obtusifolia seeds, was reported to have memory enhancing properties and anti-AD activity to ameliorate amyloid β-induced synaptic dysfunction. However, the responsible components of C. obtusifolia seeds in an AD are currently still unknown. In this study, we investigated the inhibitory effects of C. obtusifolia and its constituents against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) enzyme activity. MATERIALS AND METHODS In vitro cholinesterase enzyme assays by using AChE, BChE, and BACE1 were performed. We also scrutinized the potentials of Cassiae semen active component as BACE1 inhibitors via enzyme kinetics and molecular docking simulation. RESULTS In vitro enzyme assays demonstrated that C. obtusifolia and its major constituents have promising inhibitory potential against AChE, BChE, and BACE1. All Cassiae semen constituents exhibited potent inhibitory activities against AChE and BACE1 with IC50 values of 6.29-109µg/mL and 0.94-190µg/mL, whereas alaternin, questin, and toralactone gentiobioside exhibited significant inhibitory activities against BChE with IC50 values of 113.10-137.74µg/mL. Kinetic study revealed that alaternin noncompetitively inhibited, whereas cassiaside and emodin showed mixed-type inhibition against BACE1. Furthermore, molecular docking simulation results demonstrated that hydroxyl group of alaternin and emodin tightly interacted with the active site residues of BACE1 and their relevant binding energies (-6.62 and -6.89kcal/mol), indicating a higher affinity and tighter binding capacity of these compounds for the active site of BACE1. CONCLUSION The findings of the present study suggest the potential of C. obtusifolia and its major constituents for use in the development of therapeutic or preventive agents for AD, especially through inhibition of AChE, BChE and BACE1 activities.

Protein tyrosine phosphatase 1B and α-glucosidase inhibitory activities of Pueraria lobata root and its constituents

ETHNOPHARMACOLOGICAL RELEVANCE Pueraria lobata root was used to treat wasting-thirst regarded as diabetes mellitus and was included in the composition of Okcheonsan, which is prescribed for thirst-waste in traditional Chinese medicine. AIM OF THE STUDY The objective of this study was to evaluate the anti-diabetic potential of the root of Pueraria lobata and its constituents via protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase inhibitory activities. MATERIALS AND METHODS In this study, anti-diabetic activities of the 70% ethanolic (EtOH) extract from P. lobata roots and its solvent soluble fractions with the isolated compounds were investigated by evaluating in vitro PTP1B and α-glucosidase inhibitory activities. We also examined the potentials of active compounds as PTP1B and α-glucosidase inhibitors via enzyme kinetics and in silico molecular docking simulation between the enzymes and active compounds. RESULTS Triterpenoids lupeol and lupenone were potent PTP1B inhibitors with IC50 values of 38.89±0.17 and 15.11±1.23μM. Kinetic study using the Lineweaver-Burk and Dixon plots demonstrated that these compounds showed a noncompetitive-type inhibition against PTP1B with respective Ki values of 13.88μM and 21.24μM. In addition, molecular docking simulation showed lupeol and lupenone has negative binding energy values of -8.03 and -8.56kcal/mol. Considering the α-glucosidase inhibitory potential, daidzein, genistein, and calycosin exhibited the most potent α-glucosidase inhibition with IC50 values of 8.58±0.94, 2.37±0.52 and 6.84±1.58μM, respectively. Kinetic study demonstrated that these 3 compounds showed a noncompetitive-type inhibition against α-glucosidase with respective Ki values of 17.64μM, 5.03μM and 13.83μM. Moreover, molecular docking simulation showed daidzein, genistein and calycosin has more lower binding energy (-7.16kcal/mol, -7.42kcal/mol and -7.31kcal/mol) with higher binding affinity and tight binding capacity in the molecular docking studies than standard ligand α-D-glucose (-6.74kcal/mol). CONCLUSION Our results of the present study clearly demonstrate the potential of P. lobata extract and its constituents to inhibit PTP1B and α-glucosidase, contributing to the development of therapeutic or preventive agents that can be used in the treatment of diabetes.

Inhibitory activity of Aralia continentalis roots on protein tyrosine phosphatase 1B and rat lens aldose reductase

As part of our continuous search for compounds from natural sources that can treat diabetes and its diabetic complications, in the present work, we investigated the protein tyrosine phosphatase 1B (PTP1B) and rat lens aldose reductase (RLAR) inhibitory activities of the roots of Aralia continentalis. The methanol extract showed a potent inhibitory activity against PTP1B and RLAR. Among the tested fractions, the n-hexane fraction exhibited the highest PTP1B inhibitory activity, while the EtOAc fraction showed highest RLAR inhibitory activity. Bioassayguided fractionation of the active n-hexane and EtOAc soluble fractions resulted in the isolation of the diterpenoids; ent-pimara-8(14),15-diene-19-oic acid (continentalic acid, 1); ent-kaur-16-en-19-oic-acid (kaurenoic acid, 2); ent-pimara-8(14),15-diene-19-ol (3); 7-oxo-ent-pimara-8(14),15-diene-19-oic acid (4); 16á-hydroxy-17-isovaleroyloxy-ent-kauran-19-oic acid (5); 17-hydroxy-entkaur-15-en-19-oic acid (6); 15á,16á-epoxy-17-hydroxy-ent-kauran-19-oic acid (7); 16á,17-dihydroxy-ent-kauran-19-oic acid (8); 8á-hydroxy-ent-pimara-15-en-19-ol (9); 4-epirulopezol (10) and 4â-hydroxy-19-nor-(−)-pimara-8(14),15-diene (11), from the n-hexane fraction, and 4-[formy-5-(methoxymethyl)-1H-pyrrol-1-yl] butanoic acid (12); vanillic acid (13); 4-hydroxybenzoic acid (14); protocatechuic acid (15); nicotinic acid (16); aralia cerebroside (17); 5-O-feruloly quinic acid (18) from the EtOAc fraction. Of these, compounds 12∼14, 16 and 18 were isolated from A. continentalis for the first time. Compounds 1∼10 exhibited inhibitory potential against PTP1B, while compounds 12, 17, and 18 were found to be active against RLAR. Taken together, these results clearly demonstrate that the roots of A. continentalis displayed anti-diabetic and antidiabetic properties, which could be further explored to develop therapeutic and preventive agents for the treatment of diabetes and related complications.

BACE1 molecular docking and anti-Alzheimer's disease activities of ginsenosides

ETHNOPHARMACOLOGICAL RELEVANCE Ginsenosides are natural product steroid glycosides and triterpene saponins obtained from the Panax species. Panax ginseng has been widely used as a traditional Chinese medicine (TCM) for around a thousand years, especially in East Asian countries. Ginseng, the root and rhizome of the most popular species P. ginseng, used as tonic, prophylactic agent and restorative. In TCM, ginseng is highly valued herb and has been applied to a variety of pathological conditions and illnesses such as hypodynamia, anorexia, shortness of breath, palpitation, insomnia, impotence, hemorrhage and diabetes. AIM OF THE STUDY The basic aim of this study was to evaluate the anti-Alzheimers disease activities of selected ginsenosides (Rb1, Rb2, Rc, Re, Rg1, and Rg3) according to peroxynitrite (ONOO(‒)) scavenging activity and inhibitory activity of ONOO(-)-mediated nitrotyrosine formation as a measure of changes in oxidative stress. In addition, molecular docking simulation studies were performed to predict binding energies of the ginsenosides with β-site amyloid precursor protein cleaving enzyme 1 (BACE1, β-secretase) and identify the interacting residues. MATERIALS AND METHODS In vitro cholinesterase enzyme assays by using acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE1 were performed. In vitro authentic peroxynitrite scavenging activity and inhibitory activity against ONOO(-)-mediated nitrotyrosine formation were also performed. Molecular docking simulation studies were performed with Autodock Vina software and Discovery studio 4.1. RESULTS In vitro enzyme assays demonstrated that ginsenosides have significant inhibitory potential against AChE, BChE, and BACE1, as well as ONOO(-) and nitrotyrosine formation. Most importantly, significant AChE inhibitory activities were observed for Re; BChE for Rg3; and BACE1 for Rc, with IC50 values of 29.86±3.20, 16.80±0.36, and 59.81±2.74μg/mL, respectively. Among the tested ginsenosides, Rb1 exhibited a higher scavenging activity against ONOO(-) with an IC50 value of 27.86±1.34μg/mL, while Rc and Rg3 exhibited impressive inhibitory activity against the formation of nitrotyrosine. In addition, molecular docking studies revealed potential BACE1 inhibitory activity of ginsenosides, especially Rb1 and Rb2, which exhibited good binding affinities towards BACE1, with docking scores of -10kcal/mol. CONCLUSION The findings of the present study suggest the potential of ginsenosides (Rb1, Rb2, Rc, Re, Rg1, and Rg3) for use in the development of therapeutic or preventive agents for Alzheimers disease, especially through inhibition of AChE, BChE and BACE1 activities, as well as scavenging of ONOO(-) and inhibition of nitrotyrosine formation.

Anti-adipogenic effect of epiberberine is mediated by regulation of the Raf/MEK1/2/ERK1/2 and AMPKα/Akt pathways

It has been reported that alkaloids derived from Coptis chinensis exert anti-adipogenic activity on 3T3-L1 adipocytes by downregulating peroxisome proliferation-activity receptor-γ (PPAR-γ) and CCAAT/enhancer binding protein-α (C/EBP-α). However, the signaling-based mechanism of the inhibitory role of epiberberine in the early stages of 3T3-L1 adipocyte differentiation is uncharacterized. Here, we show that epiberberine had inhibitory effects on adipocyte differentiation and significantly decreased lipid accumulation by downregulating an adipocyte-specific transcription factor, sterol regulatory element-binding protein-1 (SREBP-1). Furthermore, we observed that epiberberine markedly suppressed the differentiation-mediated phosphorylation of components of both the Raf/mitogen-activated protein kinase 1 (MEK1)/extracellular signal-regulated protein kinase 1/2 (ERK1/2) and AMP-activated protein kinase-α1 (AMPKα)/Akt pathways. In addition, gene expression of fatty acid synthase (FAS) was significantly inhibited by treatment with epiberberine during adipogenesis. These results indicate that the anti-adipogenic mechanism of epiberberine is associated with inhibition of phosphorylation of Raf/MEK1/ERK1/2 and AMPKα/Akt, followed by downregulation of the major transcription factors of adipogenesis, such as PPAR-γ, C/EBP-α, and SREBP-1, and FAS. Taken together, this study suggests that the anti-adipogenic effect of epiberberine is mediated by downregulation of the Raf/MEK1/ERK1/2 and AMPKα/Akt pathways during 3T3-L1 adipocyte differentiation. Moreover, the anti-adipogenic effects of epiberberine were not accompanied by modulation of β-catenin.