Leishmania donovani persistence and circulation causing cutaneous leishmaniasis in unusual-foci of Nepal.

Cutaneous leishmaniasis cases have increased dramatically in recent years in Nepal. The study offers molecular identification of the Leishmania species using 40 patient's aspiration biopsy samples, targeting markers kinetoplast minicircle DNA (kDNA) and internal transcribed spacer-1 (ITS1). Among molecularly diagnosed 22 cutaneous leishmaniasis cases, L. donovani complex was identified in 13 instances and L. major in 9 cases. The ITS1 PCR was positive in 12 of the positive nested- kDNA PCR cases (12/22), confirming L. donovani complex in seven of the cases and L. major in five of the cases. In addition, the study conclude that concurrent occurrence of atypical cutaneous infections caused by L. donovani parasite in 59.1% of cases and typical cutaneous infections caused by L. major parasite in 40.9% of cases. A Phylogentic analaysis showed that the detected L. donovani species present null genetic distances from seven references of L. donovani, but slight differences between ITS1 sequences and not grouped into a significant monophyletic cluster.

Dengue virus infection during window period of consecutive outbreaks in Nepal and assessment of clinical parameters.

Nepal is an endemic country for dengue infection with rolling of every 3 year's clear cyclic outbreaks with exponential growth since 2019 outbreak and the virus gearing towards the non-foci temperate hill regions. However, the information regarding circulating serotype and genotype is not frequent. This research discusses on the clinical features, diagnosis, epidemiology, circulating serotype and genotype among 61 dengue suspected cases from different hospitals of Nepal during the window period 2017-2018 between the two outbreaks of 2016 and 2019. E-gene sequences from PCR positive samples were subjected to phylogenetic analysis under time to most recent common ancestor tree using Markov Chain Monte Carlo (MCMC) and BEAST v2.5.1. Both evolution and genotypes were determined based on the phylogenetic tree. Serotyping by Real-time PCR and Nested PCR showed the co-circulation of all the 3 serotypes of dengue in the year 2017 and only DENV-2 in 2018. Genotype V for DENV-1 and Cosmopolitan Genotype IVa for DENV-2 were detected. The detected Genotype V of DENV-1 in Terai was found close to Indian genotype while Cosmopolitan IVa of DENV-2 found spreading to geographically safe hilly region (now gripped to 9 districts) was close to South-East Asia. The genetic drift of DENV-2 is probably due to climate change and rapid viral evolution which could be a representative model for high altitude shift of the infection. Further, the increased primary infection indicates dengue venturing to new populations. Platelets count together with Aspartate transaminase and Aalanine transaminase could serve as important clinical markers to support clinical diagnosis. The study will support future dengue virology and epidemiology in Nepal.

Quantifying effects of meteorological parameters on air pollution in Kathmandu valley through regression models.

Most studies on air pollution have focused on source apportionment aspect but very few have considered meteorological factors responsible for variation in air pollution levels including studies in Nepal. Consequently, the effects of meteorological parameters including effects of seasonality and lag effects are investigated and quantified for Kathmandu valley, Nepal. Daily temporal data of air pollution for 2017-early 2020 monitored by the Department of Environment and US Embassy, Kathmandu, Nepal, and meteorological data monitored by the Department of Hydrology and Meteorology, Kathmandu, Nepal, are used. Regression models namely exponential, Box-Cox transformed and Gamma generalized linear models are used to quantify the effects supported by regression diagnostics. Results depict high proportions of observed air pollution variations (79-85%) explained by the fitted models with varied effects of meteorological parameters. Around 5% reduction in PM10 (96% CI: 0.034-0.069) and PM1 (95% CI: .0.029-0.063) levels per 1 °C increase in average temperature and significant increase in surface O3 level (0.177, 95% CI: 0.126-0.228 Box-Cox transformed value) per 1 °C increase in average temperature are detected. Similarly, around 0.7% (95% CI: 0.1-1.3) and 2% (96% CI:1.3-2.5) decrease in PM1 and PM10, respectively per 1% increase in relative humidity, 0.032 (95% CI: 0.024-0.040) decrease in transformed value of PM2.5 per 1 mm increase in rainfall, and 7.3% (95% CI: 1.3-15.9) decrease in PM10 per 1 m/s increase in wind speed are also detected. In conclusion, meteorological conditions are found significant contributing factors in determining air pollution levels in Kathmandu valley. On the long run, atmospheric conditions can play vital roles in air pollution situation shifts mainly due to climate change characterized by changes in meteorological values.

Effects of Climatic Factors on Diarrheal Diseases among Children below 5 Years of Age at National and Subnational Levels in Nepal: An Ecological Study.

Introduction: The incidence of diarrhea, a leading cause of morbidity and mortality in low-income countries such as Nepal, is temperature-sensitive, suggesting it could be associated with climate change. With climate change fueled increases in the mean and variability of temperature and precipitation, the incidence of water and food-borne diseases are increasing, particularly in sub-Saharan Africa and South Asia. This national-level ecological study was undertaken to provide evidence linking weather and climate with diarrhea incidence in Nepal. Method: We analyzed monthly diarrheal disease count and meteorological data from all districts, spanning 15 eco-development regions of Nepal. Meteorological data and monthly data on diarrheal disease were sourced, respectively, from the Department of Hydrology and Meteorology and Health Management Information System (HMIS) of the Government of Nepal for the period from 2002 to 2014. Time-series log-linear regression models assessed the relationship between maximum temperature, minimum temperature, rainfall, relative humidity, and diarrhea burden. Predictors with p-values < 0.25 were retained in the fitted models. Results: Overall, diarrheal disease incidence in Nepal significantly increased with 1 °C increase in mean temperature (4.4%; 95% CI: 3.95, 4.85) and 1 cm increase in rainfall (0.28%; 95% CI: 0.15, 0.41). Seasonal variation of diarrheal incidence was prominent at the national level (11.63% rise in diarrheal cases in summer (95% CI: 4.17, 19.61) and 14.5% decrease in spring (95% CI: −18.81, −10.02) compared to winter season). Moreover, the effects of temperature and rainfall were highest in the mountain region compared to other ecological regions of Nepal. Conclusion: Our study provides empirical evidence linking weather factors and diarrheal disease burden in Nepal. This evidence suggests that additional climate change could increase diarrheal disease incidence across the nation. Mountainous regions are more sensitive to climate variability and consequently the burden of diarrheal diseases. These findings can be utilized to allocate necessary resources and envision a weather-based early warning system for the prevention and control of diarrheal diseases in Nepal.

Cannabis terpenes display variable protective and anti-aggregatory actions against neurotoxic ß amyloid in vitro: highlighting the protective bioactivity of α-bisabolol in motorneuronal-like NSC-34 cells.

BACKGROUND: Terpenes form a diverse class of naturally occurring chemicals ascribed various biological activities. Cannabis contains over 400 different terpenes of varying chemical complexity which may add to the known biological activities of phytocannabinoids of relevance to the increasing use of medical cannabis; however, to date have been incompletely characterized. We assessed three terpenes predominant in cannabis: α-bisabolol, myrcene and ß-caryophyllene for neuroprotective and anti-aggregative properties in both undifferentiated and differentiated NSC-34 motorneuronal-like cells as a sensitive model for neurotoxicity to oxidative stress and amyloid ß (Aß1-42) protein exposure. METHODS: Cell viability was assessed biochemically using the MTT assay in the presence of either α-bisabolol, myrcene and ß-caryophyllene (1-1000 µM) for 48 hr. Sub-toxic threshold test concentrations of each terpene were then applied to cells, alone or with concomitant incubation with the lipid peroxidant tert-butyl hyrdroperoxide (t-BHP) or amyloid ß (Aß1-42; 0-1 µM) to assess neuroprotective effects. Direct effects of each terpene on Aß fibril formation and aggregation were also evaluated using the Thioflavin T (ThT) fluorometric kinetic assay, circular dichroism and transmission electron microscopy (TEM) to visualise fibril and aggregate morphology. RESULTS: Terpenes were intrinsically benign to NSC-34 cells up to 100 µM. No significant antioxidant effects were observed following t-BHP administration with myrcene and ß-caryophyllene, however α-bisabolol provided a modest but significant increase in cell viability in undifferentiated cells. α-bisabolol also demonstrated a significant neuroprotective effect against amyloid ß exposure, with ß-caryophyllene also providing a lesser, but significant increase in cell viability. Protective effects of terpenes were more pronounced in undifferentiated versus differentiated cells, attributable more so to an attenuated loss of cell viability in response to Aß1-42 following NSC-34 cell differentiation. Neuroprotection was associated with a direct inhibition of Aß1-42 fibril and aggregate density, evidenced by both attenuated ThT fluorescence kinetics and both spectral and microscopic evidence of altered and diminished density of Aß aggregates. While myrcene and ß-caryophyllene also elicited reductions in ThT fluorescence and alterations in Aß aggregation, these were less well associated with neuroprotective capacity. CONCLUSIONS: These findings highlight a neuroprotective role of α-bisabolol against Aß-mediated neurotoxicity associated with an inhibition of Aß fibrillization and modest antioxidant effect against lipid peroxidation, while ß-caryophyllene also provided a small but significant measure of protection to Aß-mediated neurotoxicity. Anti-aggregatory effects were not directly correlated with neuroprotective efficacy. This demonstrates that bioactivity of selected terpenes should be a consideration in the emergent use of medicinal cannabis formulations for the treatment of neurodegenerative diseases.

Emodin Derivatives as Multi-Target-Directed Ligands Inhibiting Monoamine Oxidase and Antagonizing Vasopressin V1A Receptors.

The brain neurotransmitter level is associated with the pathology of various neurodegenerative diseases, and age-dependent increase in the blood level of vasopressin, human brain monoamine oxidase (hMAO) level, oxidative stress, and imbalance in aminergic signaling are common disease-modifying factors leading to various neurodegenerative disorders. Based on the reports of emodin in hMAO inhibition and antagonist effect on the vasopressin V1A receptor, in this study we synthesized six emodin derivatives and evaluated their effects on MAO activity and G protein-coupled receptors. Among them, 4-hydroxyemodin and 5-hydroxyemodin were potent inhibitors of hMAO, and 2-hydroxyemodin and 5-hydroxyemodin were good V1AR antagonists. In silico molecular docking simulation revealed that the hydroxyl group at C2, C4, and C5 of the respective compounds interacted with prime residues, which corroborates the in vitro effect. Likewise, these three derivatives were predicted to have good drug-like properties. Overall, our study demonstrates that the hydroxyl derivatives of emodin are multi-target-directed ligands that may act as leads for the design and development of a therapy for central nervous system disorders.

Inhibition of PTP1B by farnesylated 2-arylbenzofurans isolated from Morus alba root bark: unraveling the mechanism of inhibition based on in vitro and in silico studies.

Among the 2-arylbenzofuran derivatives isolated from Morus alba, the farnesylated 2-arylbenzofuran is a rarer constituent. The derivative has been reported to exert anti-obesity effect; however, its inhibitory effect on protein tyrosine phosphatase 1B (PTP1B) has not been investigated. In the previous study, the presence of the farnesyl group in the structure of 2-arylbenzofurans was found to have positive influences on their pancreatic lipase inhibitory activity. In the present study, we have confirmed the authenticity of the notation based on the PTP1B inhibitory activity of farnesylated 2-arylbenzofurans. Specifically, two farnesylated 2-arylbenzofurans [morusalfurans B (2) and C (3)] showed strong inhibitory effects on PTP1B with IC50 values of 8.92 and 7.26 µM, respectively, which was significantly higher than that of the positive controls [sodium orthovanadate (IC50 = 15.10 µM) and ursolic acid (IC50 = 11.34 µM)]. Besides, two 2-arylbenzofurans [morusalfurans A (1) and F (6)], one flavonoid [morusalnol B (9)], and one geranylated stilbene [morusibene A (11)] exhibited PTP1B inhibition with IC50 values ranging from 11.02 to 26.56 µM. Kinetic studies revealed compounds 2, 3, 6, and 11 as mixed type PTP1B inhibitors, while 1 and 9 are known as noncompetitive. Molecular docking simulations demonstrated that these active compounds can bind with the respective catalytic or/and allosteric sites of PTP1B with negative binding energies and the results are in accordance with that of the kinetic studies. To the best of our knowledge, this is the first time, the PTP1B inhibitory activity of eleven compounds (1-11), as well as the mechanism of action underlying the effects on PTP1B enzyme of the active compounds, were investigated. In vitro and in silico results suggest that the farnesylated 2-arylbenzofurans from M. alba may potentially be utilized as an effective treatment therapy for type 2 diabetes mellitus and its associated complications.

Cutaneous Leishmaniasis of Lip and Role of Polymerase Chain Reaction: A Case Report.

The diagnosis of cutaneous leishmaniasis is mostly confirmed by the identification of parasite in a skin smear or biopsy. However, this method may not always be sensitive enough to detect the disease when parasitic load is low. Molecular test such as polymerase chain reactions can be useful in such circumstances. Here, we report a case of cutaneous leishmaniasis diagnosed by a polymerase chain reaction test when both smear and biopsy failed to confirm the diagnosis. A 17-years-old female from mountainous district of Nepal, presented with a crusted plaque over the upper lip for a duration of 6 months. Both skin smear and biopsy from the lesion failed to demonstrate Leishmania parasite but a polymerase chain reaction test was positive for Leishmania donovani. This case emphasizes on the importance of molecular testing such as polymerase chain reaction when commonly performed diagnostics test fails to support confirmation of clinical diagnosis.

Ecklonia radiata extract containing eckol protects neuronal cells against Aß1-42 evoked toxicity and reduces aggregate density.

Brown seaweed (Phaeophyceae) polyphenolics such as phlorotannins are ascribed various biological activities, including neuroprotection. Of these seaweeds, Ecklonia radiata (E. radiata) is found abundantly along South Australian coastal regions; however it has not been explored for various biological activities relative to any component phlorotannins previously ascribed neuroprotective capacity. In the present study, we evaluated neuroprotective activity against the neurotoxic amyloid ß protein (Aß1-42) of an ethanol extract of E. radiata compared with various additional solvent-solubilised fractions in a neuronal PC-12 cell line. The ethyl acetate fraction comprising 62% phlorotannins demonstrated the most efficacious neuroprotective activity, inhibiting neurotoxicity at all Aß1-42 concentrations. In addition, this fraction demonstrated a significant reduction in Aß aggregate density, but did not alter overall aggregate morphology. Centrifugal partitioning chromatography was used to isolate the major component, eckol, in high yield and liquid chromatography-mass spectrometry was used to characterize the major components of the ethyl acetate fraction. Our results demonstrate that the prevalence of eckol-type phlorotannins are associated with neuroprotective bioactivity of E. radiata, suggestive of potential nutraceutical and biopharmaceutical uses of this brown seaweed phlorotannin in dementia.

Molecular phylogeny and distribution of dengue virus serotypes circulating in Nepal in 2017.

Dengue virus (DENV) infection is endemic in Nepal. Although infection rates are reported annually, little information is available about the circulating viral serotypes and genotypes. Here, we report the results of a multicentre cross-sectional study of DENV serotypes and genotypes sampled from individuals with suspected DENV infection in Nepal in 2017. Of the 50 patients sampled, 40 were serologically positive for DENV NS1, 29 for anti-DENV IgM, 21 for anti-DENV IgG and 14 were positive by qRT-PCR. The three serotypes DENV-1, 2 and 3 were detected and there was no DENV-4. Positive samples from serotyping were subjected to PCR amplification by envelope (E) gene specific primer and subsequent bidirectional sequencing of 5 samples. A time to most recent common ancestor phylogenetic tree was constructed from the new sequences obtained here together with historical DENV-1 and DENV-2 E gene sequences. The DENV-1 isolates (n = 2) from Nepalese individuals were closely related to Indian genotype V, whereas DENV-2 isolates (n = 3) belonged to Cosmopolitan genotype IVa, which is closely related to Indonesian isolates. Historical DENV isolates obtained between 2004 and 2013 clustered with Cosmopolitan IVb, Cosmopolitan IVa, and Asian II genotypes. All Nepalese isolates had different lineages with distinct ancestries. With the exception of isolates obtained in 2004, all other previously published isolates had ancestry to geographically distant part of the world. Molecular analysis revealed dengue epidemics to be comprised of different genotypes of serotype 1 and 2 raising concerns on potential role of different genotypes causing Dengue hemorrhagic fever. Also, our result indicated spread of DENV-2 in non-endemic area such as hilly region of Nepal which was considered to be free of dengue due to high altitude and cold weather.

A case of high altitude cutaneous leishmaniasis in a non-endemic region in Nepal.

A case of cutaneous leishmaniasis was discovered in a 32-year old man with a persistent erythematous plaque. The patient resides in a high altitude (~2000 m above sea level) area that is not endemic for cutaneous leishmaniasis in the Dunai village of Dolpa, Nepal. The patient's lesion was initially misdiagnosed as lupus vulgaris. After response failure to initial treatment, additional testing by histological microscopy revealed the presence of Leishmania amastigotes in tissue from the lesion, and the diagnosis of cutaneous leishmaniasis was confirmed by nested PCR DNA assay of tissue from the lesion, and by a positive rK39 test in blood. Sequencing of the kinetoplast region confirmed the presence of Leishmania donovani complex. The patient responded well to treatments for cutaneous leishmaniasis and the skin lesions regressed after 6 months. This is the first known case of cutaneous leishmaniasis in a patient in Nepal who resides at high altitude in a non-endemic region. Increasing temperatures in this region of Nepal may be expanding the range of vectors that transmit cutaneous leishmaniasis.

Complete Heart Block: A Rare Complication of Takotsubo Syndrome.

Takotsubo syndrome was believed to be a rare acute cardiac event until recently with takotsubo cardiomyopathy being its most commonly recognized and often the diagnostic feature. Its diagnosis is becoming increasingly common with varied clinical manifestations most of whom have favorable clinical outcomes, yet it can be associated with life-threatening complications. We report a case of takotsubo syndrome leading to complete heart block which is a unique complication of an otherwise self-resolving disease.

In Vitro and in Silico Human Monoamine Oxidase Inhibitory Potential of Anthraquinones, Naphthopyrones, and Naphthalenic Lactones from Cassia obtusifolia Linn Seeds.

In recent years, Cassia seed extract has been reported as a neuroprotective agent in various models of neurodegeneration, mainly via an antioxidant mechanism. However, no one has previously reported the effects of Cassia seed extract and its phytochemicals on human monoamine oxidase (hMAO) enzyme activity. The seed methanol extract, the solvent-soluble fractions, and almost all isolated compounds displayed selective inhibition of hMAO-A isozyme activity. Interestingly, compounds obtusin (3), alaternin (8), aloe-emodin (9), questin (12), rubrofusarin (13), cassiaside (15), toralactone 9-O-ß-gentiobioside (26), and (3S)-9,10-dihydroxy-7-methoxy-3-methyl-1-oxo-3,4-dihydro-1H-benzo[g]isochromene-3-carboxylic acid 9-O-ß-d-glucopyranoside (38) showed the most promising inhibition of the hMAO-A isozyme with IC50 values of 0.17-11 µM. The kinetic study characterized their mode of inhibition and molecular docking simulation predicted interactions with Ile-335 and Tyr-326 in support of the substrate/inhibitor selectivity in respective isozymes. These results demonstrate that Cassia seed extract and its constituents inhibit hMAO-A enzyme activity with high selectivity and suggest that they could play a preventive role in neurodegenerative diseases, especially anxiety and depression.

Insight into the PTP1B Inhibitory Activity of Arylbenzofurans: An In Vitro and In Silico Study.

Protein tyrosine phosphatase 1B (PTP1B) plays a specific role as a negative regulator of insulin signaling pathways and is a validated therapeutic target for Type 2 diabetes. Previously, arylbenzofurans were reported to have inhibitory activity against PTP1B. However, detailed investigation regarding their structure activity relationship (SAR) has not been elucidated. The main aim of this work was to investigate the PTP1B inhibitory activity of 2-arylbenzofuran analogs (sanggenofuran A (SA), mulberrofuran D2 (MD2), mulberrofuran D (MD), morusalfuran B (MB), mulberrofuran H (MH)) isolated from the root bark of Morus alba. All compounds demonstrated potent inhibitory activity with IC50 values ranging from 3.11 to 53.47 µM. Among the tested compounds, MD2 showed the strongest activity (IC50, 3.11 µM), followed by MD and MB, while SA and MH demonstrated the lowest activity. Lineweaver-Burk and Dixon plots were used for the determination of inhibition type whereas ligand and receptor interactions were investigated in modeled complexes via molecular docking. Our study clearly supports 2-arylbenzofuran analogs as a promising class of PTP1B inhibitors and illustrates the key positions responsible for the inhibitory activity, their correlation, the effect of prenyl/geranyl groups, and the influence of resorcinol scaffold, which can be further explored in-depth to develop therapeutic agents against T2DM.

Korean Thistle (Cirsium japonicum var. maackii (Maxim.) Matsum.): A Potential Dietary Supplement against Diabetes and Alzheimer's Disease.

In the search for natural products having a dual inhibitory action on diabetes and Alzheimer's disease, this study investigated the activity of different parts of Korean thistle (Cirsium japonicum var. maackii (Maxim.) Matsum), and its fractional constituents by in vitro enzymatic and in silico molecular docking studies. Cirsium maackii has been used as a traditional medicine for the treatment of several diseases. The ethyl acetate and dichloromethane fractions of a leaf extract showed α-glucosidase and BACE1 inhibitory activity, respectively. Furthermore, the isolated compound, luteolin, exhibited concentration-dependent non-competitive inhibition against both α-glucosidase and BACE1 (IC50 = 51.27 ± 1.23 and 13.75 ± 0.26 µM; Ki value = 52.04 and 14.76 µM, respectively). Moreover, docking studies showed that luteolin formed a strong hydrogen bond with the peripheral binding amino acid residues, and hydrophobic interactions with the α-glucosidase and BACE1 enzymes. Therefore, Korean thistle may act as an important dietary supplement against diabetes and Alzheimer's disease, especially the leaves, because of the preponderance of the active component, luteolin, making Korean thistle a promising candidate for more detailed in vitro and in vivo studies.

In vitro protein tyrosine phosphatase 1B inhibition and antioxidant property of different onion peel cultivars: A comparative study.

The aim of the present study was a comparative investigation of water and 70% ethanol extracts derived from yellow and red onion (Allium cepa L.) peels against diabetes and diabetic complications. The total phenolic contents (TPCs) and total flavonoid contents (TFCs) of each cultivar, measured to assess phytochemical characteristics, showed a direct correlation with the in vitro antioxidant effects. Among the two captives, the yellow onion peel extract showed higher antioxidant activity than red one. However, all extracts exhibited significant protein tyrosine phosphatase 1B (PTP1B) inhibitory activity (IC50; 0.30-0.86 µg/ml), showing water extracts more potent (IC50; approximately 0.3 µg/mL), than the 70% ethanol extracts (IC50; approximately 0.8 µg/ml). Similarly, in insulin-resistant HepG2 cells, all extracts enhanced the glucose uptake and reduced the expression of PTP1B in a concentration-dependent manner, water extract displaying better activity. Our results overall suggest that in vitro antioxidant and antidiabetic potentials vary among red and yellow cultivars and extracting solvents, which could therefore be a promising strategy to prevent diabetes and associated complications.

PTP1B inhibitory activity and molecular docking analysis of stilbene derivatives from the rhizomes of Rheum undulatum L.

Stilbene derivatives, the principal constituent of Rheum undulatum L., are known to have a wide range of biological activities, such as anti-allergic, anti-diabetic, antioxidant, and anti-inflammatory activities. A phytochemical study on the methanol extract of Korean rhubarb (R. undulatum L.) led to the isolation of nine stilbene derivatives (1-9) and one flavonoid (10). All structures were elucidated based on a comprehensive analysis of spectroscopic data. Compound 1 (5-methoxy-cis-rhapontigenin) was elucidated as a new compound, while compound 2 (5-methoxy-trans-rhapontigenin) was isolated from a natural source for the first time. Among the isolated compounds, stilbene derivatives (7-9) showed a strong inhibitory effect on protein tyrosine phosphatase 1B (PTP1B) with IC50 values ranging from 4.25 to 6.78 µM, which was significantly higher than that of the positive control, ursolic acid (IC50 = 11.34 µM). Furthermore, for the first time, kinetic analysis and molecular docking simulations were performed in order to understand the inhibition type as well as the interaction and binding mode of the active stilbenes (7-9) with PTP1B. Our results showed that the types of PTP1B inhibition were noncompetitive for ɛ-viniferin (8) and mixed for piceatannol (7) and δ-viniferin (9). Docking simulations of these stilbenes demonstrated negative binding energies and close proximity to residues in the binding pocket of PTP1B.

Two new naphthalenic lactone glycosides from Cassia obtusifolia L. seeds.

Two new naphthalenic lactone glycosides, (3S)-9,10-dihydroxy-7-methoxy-3-methyl-1-oxo-3,4-dihydro-1H-benzo[g]isochromene-3-carboxylic acid 9-O-ß-D-glucopyranoside (1) and (3R)-cassialactone 9-O-ß-D-glucopyranoside (2) were isolated from seeds of Cassia obtusifolia Linn., along with five known compounds: (3R)-cassialactone 9-O-ß-D-gentiobioside (3), emodin 1-O-ß-gentiobioside (4), 1-hydroxyl-2-acetyl-3,8-dimethoxy-naphthalene 6-O-ß-D-apiofuranosyl-(1 → 2)-ß-D-glucopyranoside (5), rubrofusarin 6-O-ß-D-gentiobioside (6), rubrofusarin 6-O-ß-D-triglucoside (7). Structures of 1 and 2 were elucidated by NMR and HR-ESI-MS spectroscopic analysis. Their stereochemistry was determined by CD experiment. All compounds were tested for their ability to inhibit the formation of advanced glycation end-products in vitro. Compounds 1, 2, 3, 5, and 6 showed significant in vitro inhibitory activities (IC50 values of 11.63, 23.40, 7.32, 89.03, and 38.89 µM, respectively).

Structure⁻Activity Relationship of the Tyrosinase Inhibitors Kuwanon G, Mulberrofuran G, and Albanol B from Morus Species: A Kinetics and Molecular Docking Study.

Kuwanon G (KG) and benzofuran flavonoids such as mulberrofuran G (MG) and albanol B (AB) isolated from Morus sp. are reported to exhibit anti-Alzheimer's disease, anti-inflammatory, fungicidal, anti-cancer, anti-bacterial, and anti-tyrosinase properties. We investigated the inhibition of mono- and diphenolase activity of mushroom tyrosinase by KG, MG, and AB. KG and MG displayed acceptable inhibition activity compared to kojic acid. AB did not show any activity up to 350 µM. MG displayed six-fold higher inhibition of l-tyrosine oxidation (IC50 = 6.35 ± 0.45 µM) compared to kojic acid (IC50 = 36.0 µM). Kinetic studies revealed that KG and MG inhibited monophenolase activity of tyrosinase in a competitive manner. Docking simulations of KG and MG demonstrated favorable binding energies with amino acid residues of the active sites of tyrosinase. Our investigation of the structure-activity relationship of the fused benzofuran flavonoids (MG vs. AB) implicated the methyl cyclohexene ring moiety in tyrosinase inhibition. The enzyme substrate and relative structural analyses demonstrated that KG and MG from Morus sp. could be useful natural tyrosinase inhibitors in foods or cosmetics.

Structure Related Inhibition of Enzyme Systems in Cholinesterases and BACE1 In Vitro by Naturally Occurring Naphthopyrone and Its Glycosides Isolated from Cassia obtusifolia.

Cassia obtusifolia Linn. have been used to improve vision, inflammatory diseases, and as hepatoprotective agents and to promote urination from ancient times. In the present study, we investigated the influence of glycosylation of components of C. obtusifolia and structure-activity relationships (SARs) with respect to the inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and ß-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1), which are related to Alzheimer's disease (AD). All six C. obtusifolia-derived compounds, rubrofusarin (1), rubrofusarin 6-O-ß-d-glucopyranoside (2), rubrofusarin 6-O-ß-d-gentiobioside (3), nor-rubrofusarin 6-O-ß-d-glucoside (4), isorubrofusarin 10-O-ß-d-gentiobioside (5), and rubrofusarin 6-O-ß-d-triglucoside (6) showed promising inhibitory activity against AChE/BACE1. Compounds 3 and 4 showed most significant inhibition against AChE and BACE1, respectively. The SARs results emphasized the importance of gentiobiosyl moiety in the rubrofusarin for AChE inhibition, whereas the presence of hydroxyl group at C-8 and the glucosyl moiety at the C-6 position in the nor-rubrofusarin appeared to largely determine BACE1 inhibition. Kinetics and docking studies showed the lowest binding energy and highest affinity for mixed-type inhibitors, 3 and 4. Hydrophobic bonds interactions and the number of hydrogen bonds determined the strength of the protein-inhibitor interaction. These results suggest that C. obtusifolia and its constituents have therapeutic potential, and that the SARs of its active components are further explored with a view towards developing a treatment for AD.