Regulation of Autophagy Signaling Pathways by Ginseng Saponins: A Review.

Ginseng saponins ( ginsenosides), bioactive compounds derived from ginseng, are widely used natural products with potent therapeutic properties in the management of various ailments, particularly tumors, cardiovascular and cerebrovascular diseases, and immune system disorders. Autophagy, a highly regulated and multistep process involving the breakdown of impaired organelles and macromolecules by autophagolysosomes and autophagy-related genes (ATGs), has gained increasing attention as a potential target for ginsenoside-mediated disease treatment. This review aims to provide a comprehensive overview of recent research advances in the understanding of autophagy-related signaling pathways and the role of ginsenoside-mediated autophagy regulation. By delving into the intricate autophagy signaling pathways underpinning the pharmacological properties of ginsenosides, we highlight their therapeutic potential in addressing various conditions. Our findings serve as a comprehensive reference for further investigation into the medicinal properties of ginseng or ginseng-related products.

Osteoking improves OP rat by enhancing HSP90­ß expression.

Osteoporosis (OP) is a chronic bone disease that affects individuals worldwide. Osteoporosis is primarily asymptomatic, and patients with OP suffer from pain, inconvenience, economic pressure and osteoporotic fracture (OPF). Osteoking, a Traditional Chinese Medicine compound that originates from the Yi ethnic group, has been used for a number of years to treat fractures. In our previous study, osteoking exhibited therapeutic effects on rats with OPF by promoting calcium deposition. Based on bioinformatics and network pharmacology analyses of a component­target­disease database, heat shock protein HSP 90­ß (HSP90­ß), also known as HSP90­ß, was identified to be a key target of osteoking in OP. High HSP90­ß expression levels were observed in osteoporotic rats and rat bone mesenchymal stem cells (rBMSCs) following osteoking treatment. After 12 weeks of administration in vivo, there was increased bone mineral density (BMD) (P<0.05), increased bone alkaline phosphatase (P<0.05), and improved bone microstructure in the osteoking group compared with those of the negative control group. In vitro, increased calcium deposition in rBMSCs was observed after 4 weeks of osteoking treatment. These results suggest that the mechanisms of osteoking are closely associated with HSP90­ß and activate the bone morphogenetic protein (BMP) signalling pathway, primarily through BMP­2. Osteoking treatment improves OP in rats by enhancing HSP90­ß expression.

miR­378a­3p inhibits cellular proliferation and migration in glioblastoma multiforme by targeting tetraspanin 17.

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor and patients with this disease tend to have poor clinical outcome. MicroRNAs (miRs) are important regulators of a number of key pathways implicated in tumor pathogenesis. Recently, the expression of miR­378 was shown to be dysregulated in several different types of cancer, including gastric cancer, colorectal cancer and oral carcinoma. Additional studies have demonstrated that miR­378 may serve as a potential therapeutic target against human breast cancer. However, the underlying mechanisms and potential targets of miR­378a­3p involved in GBM remain unknown. The aim of the present of was to determine the effects of miR­378a­3p and its potential targets. Tetraspanin 17 (TSPAN17) is involved in the neoplastic events in GBM and is a member of the tetraspanin family of proteins. The tetraspanins are involved in the regulation of cell growth, migration and invasion of several different types of cancer cell lines, and may potentially act as an oncogene associated with GBM pathology. The results of the present study showed that high miR­378a­3p and low TSPAN17 expression levels were associated with improved survival in patients with GBM. Additionally, high levels of TSPAN17 were linked to the poor prognosis of patients with GBM aged 50­60, larger tumor sizes (≥5 cm) and an advanced World Health Organization stage. TSPAN17 was identified and confirmed as a direct target of miR­378a­3p using a luciferase reporter assay in human glioma cell lines. Overexpression of miR­378a­3p in either of U87MG or MT­330 cells decreased the expression of TSPAN17, promoted apoptosis and decreased proliferation, migration and invasion. Overexpression of TSPAN17 attenuated the aforementioned effects induced by miR­378a­3p overexpression. The present study indicated that miR­378a­3p suppresses the progression of GBM by reducing TSPAN17 expression, and may thus serve as a potential therapeutic target for treating patients with GBM.

Hepatitis C virus infection induces endoplasmic reticulum stress and apoptosis in human fetal liver stem cells.

The cellular mechanisms by which hepatitis C virus (HCV) replication might mediate cytopathic effects are controversial and not entirely clear. In this study, we found that blood-borne HCV (bbHCV) infection could lead to endoplasmic reticulum (ER)-stress and mitochondria-related/caspase-dependent apoptosis at the early stages of infection based on use of the highly efficient bbHCV cell culture model established previously. Sections of bbHCV-infected human fetal liver stem cells (hFLSCs) revealed convolution and nonlinear ER, cell vacuolization, swelling of mitochondria, and numerous double membrane vesicles (DMVs). The percentage of apoptotic hFLSCs infected by bbHCV reached 29.8% at 16 h postinfection, and the amount of cytochrome c increased remarkably in the cytosolic protein fraction. However, over time, apoptosis was inhibited due to the activation of NF-κB. The expression of NF-κB-p65, Bcl-xL, XIAP, and c-FLIPL in hFLSCs was increased significantly 24 h after in infection by bbHCV. The accelerated cell death cycles involving apoptosis, regeneration and repair by bbHCV infection might give rise to the development of cirrhosis, and ultimately to hepatocellular carcinogenesis. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Shushe acids A-D from Ganoderma applanatum.

Ganoderma applanatum is a fungus used for the prevention and treatment of a variety of disorders in China. In the present study, four new compounds, named shushe acids A-D (1-4), were isolated from the fruiting bodies of this species. Their structures were identified on the basis of spectroscopic methods. Compounds 1-4 are all natural product hybrids composed of derivatives of gallic acid, glycerol and succinic acid. None of the four compounds showed activity against the MCF-7 cell line.

Two novel antimicrobial peptides from skin venoms of spadefoot toad Megophrys minor.

Amphibian skin contains rich bioactive peptides. Especially, a large amount of antimicrobial peptides have been identified from amphibian skin secretions. Antimicrobial peptides display potent cytolytic activities against a range of pathogenic bacteria and fungi and play important defense roles. No antimicrobial peptides have been reported from toads belonging to the family of Pelobatidae. In this work, two novel antimicrobial peptides (Megin 1 and Megin 2) were purified and characterized from the skin venoms of spadefoot toad Megophrys minor (Pelobatidae, Anura, Amphibia). Megin 1 had an amino acid sequence of FLKGCWTKWYSLKPKCPF-NH2, which was composed of 18 amino acid residues and contained an intra-molecular disulfide bridge and an amidated C-terminus. Megin 2 had an amino acid sequence of FFVLKFLLKWAGKVGLEHLACKFKNWC, which was composed of 27 amino acid residues and contained an intra-molecular disulfide bridge. Both Megin 1 and Megin 2 showed potential antimicrobial abilities against bacteria and fungi. The MICs of Megin 1 against Escherichia coli, Bacillus dysenteriae, Staphylococcus aureus, Bacillus subtilis, and Candida albicans were 25, 3, 6.25, 3, and 50 µg·mL(-1), respectively. The corresponding MICs for Megin 2 were 6.25, 1.5, 12.5, 1.5, and 12.5 µg·mL(-1), respectively. They also exerted strong hemolytic activity against human and rabbit red cells. The results suggested that megin peptides in the toad skin of M. minor displayed toxic effects on both eukaryotes and prokaryotes. This was the first report of antimicrobial peptides from amphibians belonging to the family of Pelobatidae.

A Convenient and Efficient Method to Enrich and Maintain Highly Proliferative Human Fetal Liver Stem Cells.

Pluripotent human hepatic stem cells have broad research and clinical applications, which are, however, restricted by both limited resources and technical difficulties with respect to isolation of stem cells from the adult or fetal liver. In this study, we developed a convenient and efficient method involving a two-step in situ collagenase perfusion, gravity sedimentation, and Percoll density gradient centrifugation to enrich and maintain highly proliferative human fetal liver stem cells (hFLSCs). Using this method, the isolated hFLSCs entered into the exponential growth phase within 10 days and maintained sufficient proliferative activity to permit subculture for at least 20 passages without differentiation. Immunocytochemistry, immunofluorescence, and flow cytometry results showed that these cells expressed stem cell markers, such as c-kit, CD44, epithelial cell adhesion molecule (EpCAM), oval cell marker-6 (OV-6), epithelial marker cytokeratin 18 (CK18), biliary ductal marker CK19, and alpha-fetoprotein (AFP). Gene expression analysis showed that these cells had stable mRNA expression of c-Kit, EpCAM, neural cell adhesion molecule (NCAM), CK19, CK18, AFP, and claudin 3 (CLDN-3) throughout each passage while maintaining low levels of ALB, but with complete absence of cytochrome P450 3A4 (C3A4), phosphoenolpyruvate carboxykinase (PEPCK), telomeric repeat binding factor (TRF), and connexin 26 (CX26) expression. When grown in appropriate medium, these isolated liver stem cells could differentiate into hepatocytes, cholangiocytes, osteoblasts, adipocytes, or endothelial cells. Thus, we have demonstrated a more economical and efficient method to isolate hFLSCs than magnetic-activated cell sorting (MACS). This novel approach may provide an excellent tool to isolate highly proliferative hFLSCs for tissue engineering and regenerative therapies.

Development of a novel filter cartridge system with electropositive granule media to concentrate viruses from large volumes of natural surface water.

Exposure to various infectious viruses in environmental drinking water can constitute a public health risk. However, it is difficult to detect viruses in water due to their low concentration. In this study, we have developed a novel filter cartridge system containing electropositive granule media (EGM). Viruses present in large volumes of environmental samples were adsorbed onto the EGM, and then recovered by elution and poly(ethylene glycol) (PEG) concentration. To evaluate the system's efficiency in viral recovery, poliovirus (PV-1), a surrogate for enteric viruses, was used to artificially contaminate river water samples which were then assayed by quantitative real-time PCR. To optimize the concentration procedure, the eluent type, water flow rate and properties (e.g., pH, bacterial, and viral loads), were evaluated. The highest virus recovery was obtained by pumping river water at a flow rate of 300 mL/min and then pushing 3 L of an eluent containing 3× broth [1.5% (w/v) NaCl, 3% (w/v) tryptone, 1.5% (w/v) beef powder] with 0.05 mol/L glycine through the filter. Using this procedure, the recovery efficiencies of PV-1 from 10 to 100 L of spiked river water were up to 99%. In addition, this method is virus load and pH dependent. Virus recovery was maximal at a load of between 10(3.5) and 10(5.5) TCID50 and a pH ranging from 5 to 7. The bacterial load in the water has no effect on virus recovery. Different types of viruses and surface water were tested to validate the system's applicability. Results revealed that the EGM filter cartridge was able to concentrate PV-1, human adenoviruses (HAdVs) and noroviruses (HuNoVs) with high efficiency from river, lake, and reservoir water. Furthermore, it showed more efficient recovery than glass wool and 1MDS filters. These data suggest that this system provides rapid and efficient virus recovery from a large volume of natural surface water and, as such, could be a useful tool in revealing the presence of viruses in surface water.

A tripeptide (NSK) inhibits Japanese encephalitis virus infection in vitro and in vivo.

Japanese encephalitis virus (JEV) is a major pathogen that can cause acute viral encephalitis in both humans and animals. Domain III of the viral envelope protein (EDIII) is involved in binding to host cell receptor(s) to facilitate virus entry. Our previous study showed that the loop3 peptide of EDIII possesses antiviral activity against JEV infection. In this paper, we demonstrate that three residues (NSK) in loop3 are responsible for the antiviral activity of loop3 peptide. In vitro experiments showed that the tripeptide NSK could inhibit JEV infection in both BHK-21 and Neuro-2A cells by inhibiting attachment of JEV to the cells, with IC50 values of 8 µM and 6.5 µM, respectively. In vivo experiments showed that the tripeptide could increase the survival of mice challenged with JEV to 75 % when administrated intracerebrally. Therefore, this tripeptide may serve as the basis for the development of novel antiviral agents against Japanese encephalitis virus infection.

[Determination of chlorogenic acid, rutin, scopoletin and total polyphenol in tobacco by Fourier transform near infrared spectroscopy].

The objective of the present study was to investigate the feasibility of predicting chlorogenic acid, rutin, scopoletin and total polyphenol in tobacco by Fourier transform near-infrared (FT-NIR) spectroscopy. The partial least squares(PLS) regression method, second derivative and Norris derivative filter were applied in the NIR spectroscopy prediction of chlorogenic acid, rutin, scopoletin and total polyphenol in the range of 7 500 to 4 000 cm(-1). For chlorogenic acid, rutin, scopoletin and total polyphenol, the determination coefficients were 0.976 6, 0.941 9, 0.957 1 and 0.966 6, respectively. The SEP/SEC values for them were < 1.2, and the SD/SEP values for them were > 2. The root mean square error of cross validation (RMSECV) of the four calibration models were 1.938 9, 1.046 2, 0.047 9 and 2.745 2, respectively. NIR spectroscopy was compared with the conventional methods. The results show that the two methods showed no significant difference at the significant level of 0.05. NIR spectroscopy technology can accurately analyze chlorogenic acid, rutin, scopoletin and total polyphenol in tobacco.

Vitamin E modulates cigarette smoke extract-induced cell apoptosis in mouse embryonic cells.

Vitamin E (VE) can effectively prevent occurrence of lung cancer caused by passive smoking in mice. However, whether VE prevents smoking-induced cytotoxicity remains unclear. In this study, a primary culture of embryonic lung cells (ELCs) was used to observe the cytotoxic effects of cigarette smoke extract (CSE), including its influence on cell survival, cell cycle, apoptosis, and DNA damage, and also to examine the effects of VE intervention on CSE-induced cytotoxicity. Our results showed that CSE could significantly inhibit the survival of ELCs with dose- and time-dependent effects. Furthermore, CSE clearly disturbed the cell cycle of ELCs by decreasing the proportion of cells at the S and G2/M phases and increasing the proportion of cells at the G0/G1 phase. CSE promoted cell apoptosis, with the highest apoptosis rate reaching more than 40%. CSE also significantly caused DNA damage of ELCs. VE supplementation could evidently inhibit or reverse the cytotoxic effects of CSE in a dose- and time-dependent manner. The mechanism of CSE effects on ELCs and that of VE intervention might involve the mitochondrial pathway of cytochrome c-mediated caspase activation. Our study validate that VE plays a clearly protective effect against CSE-induced cytotoxicity in mouse embryonic lung cells.

Estrogen promotes benzo[a]pyrene-induced lung carcinogenesis through oxidative stress damage and cytochrome c-mediated caspase-3 activation pathways in female mice.

Estrogen may contribute to the development of smoking-induced lung cancer in women. To test this hypothesis, an mouse model was used to investigate the effects of 17 beta-estradiol (E2) on benzo[a]pyrene (B[a]P)-induced lung carcinogenesis. We found that B[a]P could cause oxidative stress damage, upregulate mitochondrial cytochrome-c and caspase-3 expression, induce lung carcinogenesis in female mice, E2 promoted these effects of B[a]P while tamoxifen (TAM) inhibited this effects of E2. We conclude that E2 can promote the tumorigenic effects of B[a]P in female mice, and oxidative stress damage and activation of cytochrome-c-mediated caspase-3 pathway may be involved in this process.

Antioxidant intervention of smoking-induced lung tumor in mice by vitamin E and quercetin.

BACKGROUND: Epidemiological and in vitro studies suggest that antioxidants such as quercetin and vitamin E (VE) can prevent lung tumor caused by smoking; however, there is limited evidence from animal studies. METHODS: In the present study, Swiss mouse was used to examine the potential of quercetin and VE for prevention lung tumor induced by smoking. RESULTS: Our results suggest that the incidence of lung tumor and tumor multiplicity were 43.5% and 1.00 +/- 0.29 in smoking group; Quercetin has limited effects on lung tumor prevention in this in vivo model, as measured by assays for free radical scavenging, reduction of smoke-induced DNA damage and inhibition of apoptosis. On the other hand, vitamin E drastically decreased the incidence of lung tumor and tumor multiplicity which were 17.0% and 0.32 +/- 0.16, respectively (p < 0.05); and demonstrated prominent antioxidant effects, reduction of DNA damage and decreased cell apoptosis (p < 0.05). Combined treatment with quercetin and VE in this animal model did not demonstrate any effect greater than that due to vitamin E alone. In addition, gender differences in the occurrence of smoke induced-lung tumor and antioxidant intervention were also observed. CONCLUSION: We conclude that VE might prevent lung tumor induced by smoking in Swiss mice.

Impacts of passive smoking on learning and memory ability of mouse offsprings and intervention by antioxidants.

OBJECTIVE: To determine the impact of passive smoking and the protective effect of antioxidants such as vitamin E and quercetin on learning and memory ability of mouse offsprings. METHODS: A passive smoking model of pregnant mice was established. Learning and memory ability was evaluated by the water maze test and long term potentiation (LTP). Nitric oxide (NO), content, nitric oxide synthase (NOS), acetylcholinesteras (Ache) activity in brain, vitamin E concentration, and reactive oxygen species (ROS) in serum were determined. The latency period (the time during which the mice swim from the starting position to the ending position) and errors (the number of mice entering the blind end) in control and antioxidant intervention groups were compared with those in the smoke exposure group after 6 days. RESULTS: The latency period as well as errors in the air, control diet, tobacco smoke (TS), and vitamin E diet groups were decreased significantly as compared with the TS and control diet groups (P<0.05). LTP was restrained in the TS and control diet groups. LTP in all the antioxidant diet groups was significantly increased compared with the TS and control diet groups. In addition, NOS and acetylcholinesteras (Ache) activitiy was significantly higher in the TS and control diet groups than in the air and control diet group. NO content was not significantly different among the different groups, and significantly lower in the TS and vitamin E diet groups than in the TS group, control diet group, quercetin diet group, and mixture diet group (P<0.05). Vitamin E concentration and ROS activity in serum were correlated with the outcome of water maze and LTP. CONCLUSION: Passive smoking reduces LTP formation by disturbing the hippocampus function of mice, by decreasing NOS and Ache activity and increasing NO content. Antioxidants (especially vitamin E) partially improve the learning and memory ability of offsprings whose mothers are exposed to tobacco smoke during pregnancy.

Copper-aspirin complex inhibits cyclooxygenase-2 more selectively than aspirin.

The antiinflammatory effects of the copper-aspirin complex (Cu-Asp) were more potent than that of Asp in rats or mice with fewer classic adverse effects. The aim of this study was to determine the cause by evaluating Cu-Asp selective inhibition on cyclooxygenases (COX). COX-1 inhibition was evaluated based on 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)) in an endothelial cell model, and COX-2 inhibition was based on prostaglandin E(2) (PGE(2)) in a macrophage model. Radioimmunoassay (RIA) was applied to determine 6-keto-PGF(1alpha) in resting human umbilical vein endothelial cell line (ECV304), and PGE(2) in activated macrophages. The results showed that the inhibition of 6-keto-PGF(1alpha) yield by Cu-Asp (3 to 0.01 mM) was markedly weaker than that by aspirin (Asp); while the inhibition of PGE(2) yield by Cu-Asp (10 to 0.1 mM) was significantly stronger than that by Asp. Based on the inhibition on 6-keto-PGF(1alpha) and PGE(2), the medium inhibitory concentration (IC(50)) of Cu-Asp on COX-1 and on COX-2 was 1.03+/-0.15 mM, and 0.32+/-0.04 mM, respectively. The selective inhibition index on COX-2, IC(50) (COX-1)/IC(50) (COX-2), of Cu-Asp was 3.33+/-0.89, while that of Asp was 0.42+/-0.12. The results suggest that, unlike Asp, Cu-Asp is a relatively selective inhibitor of COX-2 in the present models; the selectivity of Cu-Asp is about seven-fold greater than that of Asp.

A size of approximately 1 au for the radio source Sgr A* at the centre of the Milky Way.

Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the centre of our Galaxy, is the best candidate for proof, because it is the closest. Previous very-long-baseline interferometry observations (at 7 mm wavelength) reported that Sgr A* is approximately 2 astronomical units (au) in size, but this is still larger than the 'shadow' (a remarkably dim inner region encircled by a bright ring) that should arise from general relativistic effects near the event horizon of the black hole. Moreover, the measured size is wavelength dependent. Here we report a radio image of Sgr A* at a wavelength of 3.5 mm, demonstrating that its size is approximately 1 au. When combined with the lower limit on its mass, the lower limit on the mass density is 6.5 x 10(21)M(o) pc(-3) (where M(o) is the solar mass), which provides strong evidence that Sgr A* is a supermassive black hole. The power-law relationship between wavelength and intrinsic size (size proportional, variantwavelength(1.09)) explicitly rules out explanations other than those emission models with stratified structure, which predict a smaller emitting region observed at a shorter radio wavelength.

Preparation of immunomagnetic iron-dextran nanoparticles and application in rapid isolation of E.coli O157:H7 from foods.

AIM: To prepare a kind of magnetic iron-dextran nanoparticles that was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods. METHODS: Magnetic iron-dextran nanoparticles were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E.coli O157:H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimum conditions for isolating E.coli O157:H7 from food samples were established. RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 10(1) CFU/mL or even less. In the presence of 10(8) CFU/mL of other organisms, the sensitivity is 10(1)-10(2) CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g. CONCLUSION: Isolation of target bacteria by immunomagnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel.

Modulation of PAI-1 and tPA activity and thrombolytic effects of corilagin.

In this study, Charlton's and Tomihisa's methods were modified to investigate the thrombolytic effect of corilagin from the Chinese herbal plant Phyllanthus urinaria L., as well as its effect on carotid artery patency status. The activity of type 1 plasminogen activator inhibitor (PAI-1) in rat plasma or platelet-released substances and tissue-type plasminogen activator (tPA) in rat plasma was assayed by use of a chromogenic substrate. The results showed that corilagin had a dose-dependent thrombolytic effect in rats. 5 mg/kg of corilagin produced a nearly similar reperfusion rate to that of 20000 U/kg of urokinase, whereas it produced a lower reocclusion rate than urokinase. Corilagin significantly inhibited PAI-1 activity in rat plasma or platelet-released substances while it elevated plasma tPA activity, in a concentration-dependent manner. Corilagin, however, had no influence on rabbit platelet aggregation. It is indicated that corilagin inhibited PAI-1 activity and increased tPA activity, and this property of corilagin is assumed to be responsible for the thrombolytic effect. Abbreviations. PO:persistent occlusion CR:cyclic reflow PP:persistent patency PAI-1:type 1 plasminogen activator inhibitor tPA:tissue-type plasminogen activator PBS:phosphate buffer solution IC (50):50 % of inhibitory concentration PRP:platelet-rich plasma ADP:adenosine diphosphate AA:arachidonic acid PAF:platelet-activating factor

Antiplatelet aggregation activity of diterpene alkaloids from Spiraea japonica.

Six diterpene alkaloids with an atisine-type C(20)-skeleton isolated from the Chinese herbal medicines Spiraea japonica var. acuta and S. japonica var. ovalifolia, as well as eight derivatives of spiramine C and spiradine F were evaluated for the ability to inhibit aggregation of rabbit platelets induced by arachidonic acid, ADP, and platelet-activating factor (PAF) in vitro. The results showed that 12 of the 14 atisine-type diterpene alkaloids significantly inhibited PAF-induced platelet aggregation in a concentration-dependent manner, but had no effect on ADP- or arachidonic acid-induced aggregation, exhibiting a selective inhibition. It is the first report that C(20)-diterpene alkaloids inhibit PAF-induced platelet aggregation. However, spiramine C1 concentration-dependently inhibited platelet aggregation induced by PAF, ADP and arachidonic acid with IC(50) values of 30.5+/-2.7, 56.8+/-8.4 and 29.9+/-9.9 microM, respectively, suggesting a non-selective antiplatelet aggregation action. The inhibitory effect of spiramine C1 on arachidonic acid was as potent as that of aspirin. Primary studies of the structure-activity relationships for inhibition of PAF-induced aggregation showed that the oxygen substitution at the C-15 position and the presence of an oxazolidine ring in spiramine alkaloids were essential to their antiplatelet aggregation effects. These results suggest that the atisine-type alkaloids isolated from S. japonica are a class of novel antiplatelet aggregation agents.