Cardiac glycosides from the roots of Streblus asper Lour. with activity against Epstein-Barr virus lytic replication.

Cardiac glycosides (CGs) show potential broad-spectrum antiviral activity by targeting cellular host proteins. Herein are reported the isolation of five new (1-5) and eight known (7-13) CGs from the roots of Streblus asper Lour. Of these compounds 1 and 7 exhibited inhibitory action against EBV early antigen (EA) expression, with half-maximal effective concentration values (EC50) being less than 60 nM, and they also showed selectivity, with selectivity index (SI) values being 56.80 and 103.17, respectively. Preliminary structure activity relationships indicated that the C-10 substituent, C-5 hydroxy groups, and C-3 sugar unit play essential roles in the mediation of the inhibitory activity of CGs against EBV. Further enzyme experiments demonstrated that these compounds might inhibit ion pump function and thereby change the intracellular signal transduction pathway by binding to Na+/K+-ATPase, as validated by simulated molecular docking. This study is the first report that CGs can effectively limit EBV lytic replication, and the observations made in this study may be of value for lead compound development.

Cytotoxic and non-cytotoxic cardiac glycosides isolated from the combined flowers, leaves, and twigs of Streblus asper.

A new non-cytotoxic [(+)-17ß-hydroxystrebloside (1)] and two known cytotoxic [(+)-3'-de-O-methylkamaloside (2) and (+)-strebloside (3)] cardiac glycosides were isolated and identified from the combined flowers, leaves, and twigs of Streblus asper collected in Vietnam, with the absolute configuration of 1 established from analysis of its ECD and NMR spectroscopic data and confirmed by computational ECD calculations. A new 14,21-epoxycardanolide (3a) was synthesized from 3 that was treated with base. A preliminary structure-activity relationship study indicated that the C-14 hydroxy group and the C-17 lactone unit and the established conformation are important for the mediation of the cytotoxicity of 3. Molecular docking profiles showed that the cytotoxic 3 and its non-cytotoxic analogue 1 bind differentially to Na+/K+-ATPase. Compound 3 docks deeply in the Na+/K+-ATPase pocket with a sole pose, and its C-10 formyl and C-5, C-14, and C-4' hydroxy groups may form hydrogen bonds with the side-chains of Glu111, Glu117, Thr797, and Arg880 of Na+/K+-ATPase, respectively. However, 1 fits the cation binding sites with at least three different poses, which all depotentiate the binding between 1 and Na+/K+-ATPase. Thus, 3 was found to inhibit Na+/K+-ATPase, but 1 did not. In addition, the cytotoxic and Na+/K+-ATPase inhibitory 3 did not affect glucose uptake in human lung cancer cells, against which it showed potent activity, indicating that this cardiac glycoside mediates its cytotoxicity by targeting Na+/K+-ATPase but not by interacting with glucose transporters.

In Vivo Anti-diarrheal Activity of Methanolic Extract of Streblus asper Leaves Stimulating the Na+/K+-ATPase in Swiss Albino Rats.

Streblus asper Lour., traditionally used for anti-diarrheal effects as like dysentery and diarrhea. The present study aims to prove the anti-diarrheal activities of methanolic extract of leaves of S. asper in animal models. The anti-diarrheal activity was evaluated using castor oil-induced diarrhea and magnesium sulphate-induced diarrhea models whereas anti-motility activities were investigated using gastrointestinal transit test examined in animal models. In castor oil-induced diarrhea model, methanolic extract of S. asper (MESA) at the doses of 100, 200, and 400 mg/kg produced statistically significant (P < 0.001) decreased the number of diarrheal feces of rats against castor oil-induced diarrhea as well as magnesium sulphate-induced diarrhea model also showed the same manner. In gastrointestinal transit test, delayed gastric emptying time decreased significantly (P < 0.001), the propulsion of charcoal meal in the gastrointestinal tract which also showed a dose-dependent manner in rats. The recent study indicates that MESA possesses anti-diarrheal property. The findings represent a rational explanation for its use in traditional medicine for the management of diarrhea management.

Characterization, quantitation, similarity evaluation and combination with Na+,K+-ATPase of cardiac glycosides from Streblus asper.

Streblus asper Lour. (Moraceae) is a medicinal plant in Asian countries including India and Thailand, possessing activities of anti-tumor, anti-allergy, anti-parasitic and anti-bacterial. In this paper, characterization, quantitation and similarity evaluation of cardiac glycosides in different parts of S. asper were investigated by HPLC-Q-TOF-MS and chemometric methods. Then, the inhibition of Na+,K+-ATPase activity by the compounds isolated from S. asper was measured. Meanwhile, enzyme kinetics and molecular docking were determined to exhibit the combination modes between cardiac glycosides and Na+,K+-ATPase. As a result, twenty peaks of cardiac glycosides were assigned. Strophanthidin-3-O-α-l-rhamnopyranosyl-(1 → 4)-6-deoxy-ß-d-allopyranoside (1), glucostrebloside (2), strebloside (4) and mansonin (8) with a significant activity of inhibiting Na+,K+-ATPase (IC50 7.55-13.60 µM) were chosen for the determination of enzyme kinetics, exhibiting anticompetitive inhibitory characteristics towards Na+,K+-ATPase. Compound 4 could reasonably bind to the active sites of Na+,K+-ATPase, proved by molecular docking. Furthermore, the contents of the major compounds in four different parts of S. asper were extremely different, analyzed by chemometric methods, similarity analysis and principle compounds analysis. All these findings indicated that the contents of major compounds in different parts of S. asper were extremely different with a significant activity of inhibiting Na+,K+-ATPase, providing a reference for determination of effective part and administered dosage. The combination modes between cardiac glycosides and Na+,K+-ATPase were also revealed by enzyme kinetics and molecular docking, which provided a basis for further study of pharmacological activity.

Acid-base fractions separated from Streblus asper leaf ethanolic extract exhibited antibacterial, antioxidant, anti-acetylcholinesterase, and neuroprotective activities.

BACKGROUND: Streblus asper is a well-known plant native to Southeast Asia. Different parts of the plant have been traditionally used for various medicinal purposes. However, there is very little scientific evidence reporting its therapeutic benefits for potential treatment of Alzheimer's disease (AD). The study aimed to evaluate antibacterial, antioxidant, acetylcholinesterase (AChE) inhibition, and neuroprotective properties of S. asper leaf extracts with the primary objective of enhancing therapeutic applications and facilitating activity-guided isolation of the active chemical constituents. METHODS: The leaves of S. asper were extracted in ethanol and subsequently fractionated into neutral, acid and base fractions. The phytochemical constituents of each fraction were analyzed using GC-MS. The antibacterial activity was evaluated using a broth microdilution method. The antioxidant activity was determined using DPPH and ABTS radical scavenging assays. The neuroprotective activity against glutamate-induced toxicity was tested on hippocampal neuronal HT22 cell line by evaluating the cell viability using MTT assay. The AChE inhibitory activity was screened by thin-layer chromatography (TLC) bioautographic method. RESULTS: The partition of the S. asper ethanolic leaf extract yielded the highest mass of phytochemical constitutions in the neutral fraction and the lowest in the basic fraction. Amongst the three fractions, the acidic fraction showed the strongest antibacterial activity against gram-positive bacteria. The antioxidant activities of three fractions were found in the order of acidic > basic > neutral, whereas the decreasing order of neuroprotective activity was neutral > basic > acidic. TLC bioautography revealed one component in the neutral fraction exhibited anti-AChE activity. While in the acid fraction, two components showed inhibitory activity against AChE. GC-MS analysis of three fractions showed the presence of major phytochemical constituents including terpenoids, steroids, phenolics, fatty acids, and lipidic plant hormone. CONCLUSIONS: Our findings have demonstrated the therapeutic potential of three fractions extracted from S. asper leaves as a promising natural source for neuroprotective agents with additional actions of antibacterials and antioxidants, along with AChE inhibitors that will benefit in the development of new natural compounds in therapies against AD.

Ethanolic extract of Streblus asper leaves protects against glutamate-induced toxicity in HT22 hippocampal neuronal cells and extends lifespan of Caenorhabditis elegans.

BACKGROUND: Although such local herb as Streblus asper (family Moraceae) has long been recognized for traditional folk medicines and important ingredient of traditional longevity formula, its anti-neurodegeneration or anti-aging activity is little known. This study aimed to investigate the neuroprotective effect of S. asper leaf extracts (SA-EE) against toxicity of glutamate-mediated oxidative stress, a crucial factor contributing to the neuronal loss in age-associated neurodegenerative diseases and the underlying mechanism as well as to evaluate its longevity effect. METHODS: Using mouse hippocampal HT22 as a model for glutamate oxidative toxicity, we carried out MTT and LDH assays including Annexin V-FITC/propidium iodide staining to determine the SA-EE effect against glutamate-induced cell death. Antioxidant activities of SA-EE were evaluated using the radical scavenging and DCFH-DA assays. To elucidate the underlying mechanisms, SA-EE treated cells were analyzed for the expressions of mRNA and proteins interested by immunofluorescent staining, western blot analysis and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) techniques. The longevity effect of SA-EE was examined on C. elegans by lifespan assay. RESULTS: We demonstrate that a concentration-dependent reduction of glutamate-induced cytotoxicity was significant after SA-EE treatment as measured by MTT and LDH assays. Annexin V-FITC/propidium iodide and immunofluorescent staining showed that co-treatment of glutamate with SA-EE significantly reduced apoptotic-inducing factor (AIF)-dependent apoptotic cell death. DCFH-DA assay revealed that this extract was capable of dose dependently attenuating the ROS caused by glutamate. Western blot analysis and qRT-PCR showed that nuclear factor erythroid 2-related factor 2 (Nrf2) protein levels in the nucleus, as well as mRNA levels of antioxidant-related genes under Nrf2 regulation were significantly increased by SA-EE. Furthermore, this extract was capable of extending the lifespan of C. elegans. CONCLUSIONS: SA-EE possesses both longevity effects and neuroprotective activity against glutamate-induced cell death, supporting its therapeutic potential for the treatment of age-associated neurodegenerative diseases.

Cardiac glycosides from Streblus asper with potential antiviral activity.

Ten undescribed cardiac glycosides, strasperosides A-J, together with twelve known analogues, were isolated from Streblus asper Lour. Their structures were elucidated on the basis of spectroscopic analysis, electronic circular dichroism data, and chemical methods. These cardiac glycosides showed diversity in steroid skeleton and sugar moiety. Strasperosides A and B are a pair of unusual stereoisomers featuring different orientation of the lactone motif. Ten cardiac glycosides demonstrated potent antiviral effects on HSV-1 in vitro with the IC50 values from 0.19 ± 0.08 to 1.03 ± 0.25 µM and the therapeutic indices from 66.61 ± 5.08 to 326.75 ± 11.75.

Chemical Constituents from Streblus taxoides Wood with Their Antibacterial and Antityrosinase Activities Plus in Silico Study.

Hyperpigmentation frequently occurs after inflammation from bacterial infection. Thus, the inhibition activity of tyrosinase, the key enzyme to catalyze the melanogenesis and/or inhibition of bacterial infection, could decrease melanin production. Hence, the potential inhibitors could be discovered from natural products. ω-Hydroxymoracin C (1), a new compound with two other 2-arylbenzofurans, i.e., moracin M (2) and moracin C (3), and two stilbenes, i.e., 3, 4, 3', 5'-tetrahydroxybibenzyl (4) and piceatannol (5), were isolated from the wood of Streblus taxoides. Compound 4 showed a strong inhibitory activity against tyrosinase enzyme with an IC50 value of 35.65 µg/mL, followed by compound 2 with an IC50 value of 47.34 µg/mL. Conversely, compound 1, 3 and 5 showed moderate activity, with IC50 values of 109.64, 128.67 and 149.73 µg/mL, respectively. Moreover, compound 1 and 3 showed an antibacterial effect against some Staphylococcus spp. Thus, the isolated compounds exhibited potential antityrosine and antibacterial effects. Additionally, an in silico study was performed in order to predict theoretical molecular interactions between the obtained metabolites from S. taxoides and tyrosinase as an extended in vitro enzyme binding assay experiment.

Megastigmane glycosides from Streblus ilicifolius (S.Vidal) Corner and their anti-inflammatory activity.

Twelve undescribed megastigmane glycosides, streilicifolosides A-L (1-12), together with 8 known analogues (13-21) were isolated from the leaves of Streblus ilicifolius (S.Vidal) Corner. Their plannar structures were elucidated using extensive NMR spectroscopic methods (1D and 2D-NMR spectroscopy), and HRESIMS spectroscopic data analyses. The absolute configurations of the undescribed compounds were determined by the glucose-induced shift-trend, calculated and experimental circular dichroism spectroscopy. All the compounds were tested for inhibitory effects on the production of NO in LPS-treated RAW264.7 cells, and streilicifoloside E and platanionoside D exhibited potent anti-inflammatory activity comparable to that of the positive control, with IC50 values of 26.33 and 21.84 µM, respectively. Furthermore, these two compounds markedly decreased the secretion of PGE2 and TNF-α and inhibited the expression of COX‒2, iNOS and NF-κB/p65 in LPS-induced RAW264.7 cells in a dose-dependent manner. In addition, the structure-activity relationships of the isolates were also discussed. The results suggest that streilicifoloside E and platanionoside D could be used as potential candidates for the development of new anti-inflammatory agents.

The potency of herbal extracts and its green synthesized nanoparticle formulation as antibacterial agents against Streptococcus mutans associated biofilms.

This study aims to determine the effects of the extracts of Streblus asper, Cymbopogon citratus, Syzygium aromaticum and its formulation of green synthesized silver nanoparticle (AgNPs) on Streptococcus mutans growth and biofilm formation. The ethanolic extracts of S. asper, C. citratus, S. aromaticum, and a mix of the three herbs demonstrated antibacterial activity against S. mutans isolates by reducing bacterial biofilm formation and decreasing bacterial cell surface hydrophobicity. The formulated AgNPs from the ethanolic extracts could enhance the antibacterial activities of the plant extracts. Molecular docking found the best interaction between luteolin isolated from C. citratus and glucosyltransferase protein (GtfB), assuming the promising anti-biofilm activity. The scanning electron microscopy revealed morphological changes in the biofilm structure and a significant decrease in the biofilm area of the AgNPs treated. The study suggested that the extracts and its application could be used as natural alternative agents with multi-action against S. mutans infections.

Anti-inflammatory and analgesic effects of Streblus indicus.

The bark of Streblus indicus, a Dai medicine in China, has been listed in the Chinese Materia Medica as possessing hemostatic and analgesic properties. Ethnic medicine books record that its bark or leaves for the treatment of mumps and lymphoma. However, according to the literature survey, anti-inflammatory and analgesic studies available for leaves and branches of S. indicus have been seldom reported so far. The current study focuses on the metabolites of S. indicus bark and leaves responsible for anti-inflammatory and analgesic effects on the basis of bioactive-included acetic acid writhing, hot-plate, and xylene-induced ear swelling. The secretion of inflammatory mediators, TNF-α, IL-6, IL-1ß, IL-4, and IL-10, were evaluated for their anti-inflammatory by xylene-induced in mouse ear cells. Histological examination was used to assess the anti-inflammatory and analgesic effects of the branches and leaves of S. indicus, and Western blot analysis determined the mechanism of the methanolic extract of branches and leaves. Different metabolites of S. indicus significantly alleviated analgesic and anti-inflammatory effects, with no discernable differences among them. All metabolites decreased the levels of TNF-α, IL-1ß, and IL-6 and increased the levels of IL-4 and IL-10. The analgesic and anti-inflammatory mechanism of the methanolic extract was related to the NF-kB signaling pathway. These results not only would account for scientific knowledge for the traditional application of S. indicus, but also provide a credible theoretical foundation for the further development of anti-inflammatory and analgesic agents.

Two new derivatives of 8-prenyl-5,7-dihydroxycoumarin from the stems of Streblus ilicifolius (S.Vidal) Corn.

From the EtOAc-soluble extract of the stems of Streblus ilicifolius (Moraceae), two new secondary metabolites named strebluses A (1) and B (2) were isolated. Their chemical structures have been concluded based on the chemical derivatisation and the spectroscopic interpretation. All compounds have been tested for their tyrosinase inhibitory activity. They showed weaker inhibitory activity than that of kojic acid (IC50, 44.6 µM).[Formula: see text].

Cytotoxic cardiac glycosides from the root of Streblus asper.

Bioassay-guided separation of the root of Streblus asper led to the identification of six undescribed cardiac glycosides, including a rare cardiac glycoside dimer, along with twelve previously reported analogues. Their structures were determined on the basis of analyses of spectroscopic methods (1D and 2D-NMR spectroscopy), high-resolution electrospray ionization mass spectrometry (HRESIMS), circular dichroism (CD), and comparison of their spectroscopic data with previously reported data. Regarding their cytotoxic activities, microculture tetrazolium assays showed that all isolated cardiac glycosides strongly inhibited MCC-803, T24, SKOV-3, HepG2, Wi-38, and A549 cancer cell lines, with IC50 values ranging from 0.075 µM to 0.752 µM. One cardiac glycoside, a rare cardiac glycoside dimer, exhibited the strongest activity against the six cancer cell lines, with IC50 values ranging from 0.075 µM to 0.214 µM. In addition, the structure-activity relationships (SARs) of cardiac glycosides were investigated. In summary, S. asper showed marked cytotoxicity to several cancer cell lines, which could be meaningful for discovering new anticancer agents.

Two new amide glycosides with anti-inflammatory activity from the leaves of Streblus ilicifolius (Vidal) Corner.

Two new amide glycosides, streblusoamides A (1) and B (2), along with 11 known compounds (3-13) were isolated from the leaves of Streblus ilicifolius. The structures of the isolates were elucidated by spectroscopic methods. All of the isolates were tested for inhibition of NO production in lipopolysaccharide (LPS)-induced RAW 264.7 cells to investigate their anti-inflammatory effects. The results revealed that compounds 1, 5 and 6 moderately inhibited the release of NO production with IC50 values ranging from 50.90 µM to 64.79 µM.

Cardiac glycosides from the roots of Streblus asper Lour. and their apoptosis-inducing activities in A549 cells.

Phytochemical investigation of the roots of Streblus asper Lour. resulted in the isolation of six previously undescribed cardiac glycosides, designated 2'-de-O-methylstrebloside (1), cannogenol-3α-O-ß-D-gluopyranosyl-(1 â†’ 4)-6-deoxy -2,3-dimethoxyl-ß-D-fucopyranoside (2), periplogenin-3-O-α-L-rhamnopyranosyl -(1 â†’ 4)-6-deoxy-ß-D-allopyranoside (3), 5-de-O-hydroxylstrebloside (4), 5ßH-16ß-hydroxylkamaloside (5), and 17S, 21R-21-hydroxylstrebloside (6), and three known analogues (7-9). The structures were elucidated using NMR spectroscopic techniques, mass spectrometry, and comparison of the spectroscopic data with previously reported data. Compound 6 is a novel C-21 hydroxyl cardiac glycoside, its absolute configuration was established from the analysis of computational ECD calculations and NMR spectroscopic data. The effects of the cardiac glycosides on apoptosis and cytotoxicity were examined in human A549 lung cancer cells. All the compounds showed remarkable inhibitory activities, with IC50 values in the range of 0.01-6.08 µM. Furthermore, compound 3 was able to significantly inhibit A549 cell growth proliferation via the induction of apoptosis, due to the activation of caspases-3, -8 and -9 in A549 cells, as revealed by Western blot analysis.

Bioactivity-guided isolation of anti-inflammatory constituents from the bark of Streblus zeylanicus.

Based on anti-inflammatory activity to evaluate the effects to the release of NO, bio-assay guided separation of the bark of Streblus zeylanicus led to identify fifteen compounds, including four new terpenes (1, 2, 9, and 10), one new pentanoid glycoside (12), one new rumenic ester (13), together with nine known compounds (3-8, 11, 14, and 15). Their structures were elucidated using extensive NMR and HRESIMS spectroscopic data analyses. The stereochemistry of compound 10 was established by comparing the calculated and experimental ECD spectroscopic data. Compounds 1 and 2 showed moderate inhibition on nitric oxide (NO) production, with IC50 values of 10.21 µM and 15.53 µM, respectively.

The complete chloroplast genome of Streblus indicus.

The first complete chloroplast genome sequences of Streblus indicus were reported in this study. The cpDNA of S. indicus is 159,853 bp in length, contains a large single copy region (LSC) of 88,950 bp and a small single copy region (SSC) of 19,313 bp, which were separated by a pair of inverted repeat (IR) regions of 25,795 bp. The genome contains 129 genes, including 84 protein-coding genes, eight ribosomal RNA genes, and 37 transfer RNA genes. The overall GC content of the whole genome is 36.1%. Phylogenetic analysis of 14 chloroplast genomes within the family Moraceae shows that S. indicus clustered in a unique clade.

Two new coumarins from the bark of Streblus indicus (Bur.) Corner.

Two new coumarins 7-O-(6-O-(5-O-3,4,5-tri-methoxycinnamate-ß-d-apiofuranosyl-ß-d-glucopyranosyl)-6-methoxy coumarin (1) and 7-O-(6-O-(4-(2-hydroxy-1-hydroxymethyl-ethoxy)-3-methoxy-cinnamyl)-ß-d-glucopyranosyl)-6-methoxy coumarin (2), along with 10 known metabolites, were isolated from the bark of Streblus indicus, their structures were identified by comparison of experimental and published spectroscopic data. (S)-marmesinin (6) and scoparone (7) exhibited moderate antimicrobial activity in vitro against Staphylococcus aureus strain with the MIC values of 62.5 and 125.0 µg/mL, respectively. Betulinic acid showed inhibitory activity in vitro against MCF-7 cell with IC50 value of 9.5 ± 0.1 µM.

Benzofuran glycosides and coumarins from the bark of Streblus indicus (Bur.) Corner.

Two pairs of rare benzofuran glucoside epimers, indicuses A and B and indicuses C and D, three biogenetically related compounds indicuses E-G, and one coumarin indicus H, as well as 11 known compounds, were isolated from the bark of Streblus indicus (Bur.) Corner. The structures of indicuses A-H were elucidated by NMR and MS data, as well as by CD. (S)-Marmesinin exhibited moderate antimicrobial activity in vitro against Bacillus subtilis and Saccharomyces cerevisiae. 7,8-Dihydroxy-3-(3-methyl-2-butenyl) coumarin, umbelliferone, and scopoletin displayed strong cytotoxic activity in vitro against human bladder carcinoma cell line EJ. The structure-activity relationships indicate that hydroxylation at C-7 in the cytotoxic compounds is crucial to their activities.

Antitumor activity and antioxidant status of Streblus asper bark against Dalton's ascitic lymphoma in mice.

Streblus asper Lour (Moraceae), commonly known as Siamee Rough Brush in English is widely distributed in subtropical Asia and traditionally used for several medicinal purposes. In the present study, the ethyl acetate fraction of the methanol extract from Streblus asper bark (EASA) was evaluated for antitumor effect against Dalton's ascitic lymphoma (DAL) in Swiss albino mice. Twenty-four hours after intraperitoneal inoculation of DAL cells in mice, EASA was administered intraperitoneally at 200 and 400 mg/kg body weight for 9 consecutive days. On the 10th day, half of the mice were sacrificed to determine the tumor growth parameters, and the rest were kept alive for survival assessment. Hematological, serum biochemical and tissue (liver, kidney) antioxidant profiles were also determined. EASA exhibited significant and dose dependent decrease in tumor growth parameters and increased survival of DAL bearing animals. EASA significantly and dose-dependently normalized the altered hematological, serum biochemical and tissue antioxidant parameters as compared with the DAL control mice. From the present study it may be concluded that S. asper bark possesses remarkable antitumor efficacy mediated by amelioration of oxidative stress by multiple mechanisms.