Gaps in forensic toxicological analysis: The veiled abrin

Abrus precatorius is an herbaceous, flowering plant that is widely distributed in tropical and subtropical regions. Its toxic component, known as abrin, is classified as one of the potentially significant biological warfare agents and bioterrorism tools due to its high toxicity. Abrin poisoning can be utilized to cause accidents, suicides, and homicides, which necessitates attention from clinicians and forensic scientists. Although a few studies have recently identified the toxicological and pharmacological mechanisms of abrin, the exact mechanism remains unclear. Furthermore, the clinical symptoms and pathological changes induced by abrin poisoning have not been fully characterized, and there is a lack of standardized methods for identifying biological samples of the toxin. Therefore, there is an urgent need for further toxicopathologic studies and the development of detection methods for abrin in the field of forensic medicine. This review provides an overview of the clinical symptoms, pathological changes, metabolic changes, toxicologic mechanisms, and detection methods of abrin poisoning from the perspective of forensic toxicology. Additionally, the evidence on abrin in the field of forensic toxicology and forensic pathology is discussed. Overall, this review serves as a reference for understanding the toxicological mechanism of abrin, highlighting the clinical applications of the toxin, and aiding in the diagnosis and forensic identification of toxin poisoning.

Abrus precatorius Leaf Extract Stimulates Insulin-mediated Muscle Glucose Uptake: In vitro Studies and Phytochemical Analysis

Diabetes mellitus, linked with insulin resistance and hyperglycaemia, is a leading cause of mortality. Glucose uptake through glucose transporter type 4, especially in skeletal muscle, is crucial for maintaining euglycaemia and is a key pathway targeted by antidiabetic medication. Abrus precatorius is a medicinal plant with demonstrated antihyperglycaemic activity in animal models, but its mechanisms are unclear.This study evaluated the effect of a 50% ethanolic (v/v) A. precatorius leaf extract on (1) insulin-stimulated glucose uptake and (2) related gene expression in differentiated C2C12 myotubes using rosiglitazone as a positive control, and (3) generated a comprehensive phytochemical profile of A. precatorius leaf extract using liquid chromatography-high resolution mass spectrometry to elucidate its antidiabetic compounds. A. precatorius leaf extract significantly increased insulin-stimulated glucose uptake, and insulin receptor substrate 1 and Akt substrate of 160 kDa gene expression; however, it had no effect on glucose transporter type 4 gene expression. At 250 µg/mL A. precatorius leaf extract, the increase in glucose uptake was significantly higher than 1 µM rosiglitazone. Fifty-five phytochemicals (primarily polyphenols, triterpenoids, saponins, and alkaloids) were putatively identified, including 24 that have not previously been reported from A. precatorius leaves. Abrusin, precatorin I, glycyrrhizin, hemiphloin, isohemiphloin, hispidulin 4'-O-β-D-glucopyranoside, homoplantaginin, and cirsimaritin were putatively identified as known major compounds previously reported from A. precatorius leaf extract. A. precatorius leaves contain antidiabetic phytochemicals and enhance insulin-stimulated glucose uptake in myotubes via the protein kinase B/phosphoinositide 3-kinase pathway by regulating insulin receptor substrate 1 and Akt substrate of 160 kDa gene expression. Therefore, A. precatorius leaves may improve skeletal muscle insulin sensitivity and hyperglycaemia. Additionally, it is a valuable source of bioactive phytochemicals with potential therapeutic use for diabetes.

From Tea to Health: Exploring Abrus mollis for Liver Protection and Unraveling Its Potential Mechanisms

Abrus mollis Hance is a characteristic medicinal herb which is used in Guangdong and Guangxi provinces of China for making soup, medicinal meals, and herbal tea to treat dampheat jaundice and rib discomfort. Current phytochemical study on A. mollis led to the isolation of four new flavones, mollisone A-D (1-4), and thirty two known compounds (5-36). Their structures were characterized by an extensive analysis of spectroscopic data including IR, UV, HR-ESI-MS, and 1D and 2D NMR, as well as electronic circular dichroism calculation. In addition, in order to initially understand their biological activities for traditional applications, in vitro antioxidant and hepatoprotective tests were carried out, whose results illustrated that 25 compounds had significant free radical scavenging ability, and compounds 13 and 16 exhibited protective activities on D-GalN-induced LO2 cell damage than the positive control. Moreover, network pharmacological analysis revealed that the hepatoprotective activity of A. mollis involved multitargets and multipathways such as PI3K/Akt, MAPK, and JAK-STAT pathways and various biological processes such as positive regulation of phosphorylation and regulation of kinase activity. These results suggested that this species could serve as a potential hepatoprotective agent for functional food or medicinal use.

Neutralizing Monoclonal Antibody, mAb 10D8, Is an Effective Detoxicant against Abrin-a Both In Vitro and In Vivo

Abrin is a types II ribosome-inactivating protein (RIP) isolated from Abrus precatorious seeds, which comprises a catalytically active A chain and a lectin-like B chain linked by a disulfide bond. Four isotoxins of abrin have been reported with similar amino-acid composition but different cytotoxicity, of which abrin-a is the most potent toxin. High lethality and easy availability make abrin a potential bioterrorism agent. However, there are no antidotes available for managing abrin poisoning, and treatment is only symptomatic. Currently, neutralizing antibodies remain the most effective therapy against biotoxin poisoning. In this study, we prepared, identified, and acquired a high-affinity neutralizing monoclonal antibody (mAb) 10D8 with a potent pre- and post-exposure protective effect against cytotoxicity and animal toxicity induced by abrin-a or abrin crude extract. The mAb 10D8 could rescue the mouse injected intraperitoneally with a 25 × LD₅₀ dose of abrin-a from lethality and prevent tissue damages. Results indicated that 10D8 does not prevent the binding and internalization of abrin-a to cells but inhibits the enzymatic activity of abrin-a and reduces protein synthesis inhibition of cells. The high affinity, good specificity, and potent antitoxic efficiency of 10D8 make it a promising candidate for therapeutic antibodies against abrin.

Abrus precatorius Leaf Extract Reverses Alloxan/Nicotinamide-Induced Diabetes Mellitus in Rats through Hormonal (Insulin, GLP-1, and Glucagon) and Enzymatic (α-Amylase/α-Glucosidase) Modulation

BACKGROUND

Abrus precatorius is used in folk medicine across Afro-Asian regions of the world. Earlier, glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) was confirmed experimentally in STZ/nicotinamide-induced diabetic rats; however, the underlying mechanism of antidiabetic effect and pancreato-protection remained unknown.

OBJECTIVE

This study elucidated antidiabetic mechanisms and pancreato-protective effects of APLE in diabetic rats.

MATERIALS AND METHODS

APLE was prepared by ethanol/Soxhlet extraction method. Total phenols and flavonoids were quantified calorimetrically after initial phytochemical screening. Diabetes mellitus (DM) was established in adult Sprague-Dawley rats (weighing 120-180 g) of both sexes by daily sequential injection of nicotinamide (48 mg/kg; ip) and Alloxan (120 mg/kg; ip) over a period of 7 days. Except control rats which had fasting blood glucose (FBG) of 4.60 mmol/L, rats having stable FBG (16-21 mmol/L) 7 days post-nicotinamide/Alloxan injection were considered diabetic and were randomly reassigned to one of the following groups (model, APLE (100, 200, and 400 mg/kg, respectively; po) and metformin (300 mg/kg; po)) and treated daily for 18 days. Bodyweight and FBG were measured every 72 hours for 18 days. On day 18, rats were sacrificed under deep anesthesia; organs (kidney, liver, pancreas, and spleen) were isolated and weighed. Blood was collected for estimation of serum insulin, glucagon, and GLP-1 using a rat-specific ELISA kit. The pancreas was processed, sectioned, and H&E-stained for histological examination. Effect of APLE on enzymatic activity of alpha (α)-amylase and α-glucosidase was assessed. Antioxidant and free radical scavenging properties of APLE were assessed using standard methods.

RESULTS

APLE dose-dependently decreased the initial FBG by 68.67%, 31.07%, and 4.39% compared to model (4.34%) and metformin (43.63%). APLE (100 mg/kg) treatment restored weight loss relative to model. APLE increased serum insulin and GLP-1 but decreased serum glucagon relative to model. APLE increased both the number and median crosssectional area (×106 μm2) of pancreatic islets compared to that of model. APLE produced concentration-dependent inhibition of α-amylase and α-glucosidase relative to acarbose. APLE concentration dependently scavenged DPPH and nitric oxide (NO) radicals and demonstrated increased ferric reducing antioxidant capacity (FRAC) relative to standards.

CONCLUSION

Antidiabetic effect of APLE is mediated through modulation of insulin and GLP-1 inversely with glucagon, noncompetitive inhibition of α-amylase and α-glucosidase, free radical scavenging, and recovery of damaged/necro-apoptosized pancreatic β-cells.

Differentiation, Quantification and Identification of Abrin and Abrus precatorius Agglutinin

Abrin, the toxic lectin from the rosary pea plant Abrus precatorius, has gained considerable interest in the recent past due to its potential malevolent use. However, reliable and easy-to-use assays for the detection and discrimination of abrin from related plant proteins such as Abrus precatorius agglutinin or the homologous toxin ricin from Ricinus communis are sparse. To address this gap, a panel of highly specific monoclonal antibodies was generated against abrin and the related Abrus precatorius agglutinin. These antibodies were used to establish two sandwich ELISAs to preferentially detect abrin or A. precatorius agglutinin (limit of detection 22 pg/mL for abrin; 35 pg/mL for A. precatorius agglutinin). Furthermore, an abrin-specific lateral flow assay was developed for rapid on-site detection (limit of detection ~1 ng/mL abrin). Assays were validated for complex food, environmental and clinical matrices illustrating broad applicability in different threat scenarios. Additionally, the antibodies turned out to be suitable for immuno-enrichment strategies in combination with mass spectrometry-based approaches for unambiguous identification. Finally, we were able to demonstrate for the first time how the developed assays can be applied to detect, identify and quantify abrin from a clinical sample derived from an attempted suicide case involving A. precatorius.

Glucose lowering and pancreato-protective effects of Abrus Precatorius (L.) leaf extract in normoglycemic and STZ/Nicotinamide - Induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abrus precatorius (L.) leaves are used as folk medicine by the local communities in the western region of Ghana to treat diabetes mellitus; however, this health claim remains unverified scientifically.

OBJECTIVE

The study investigated glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) in normoglycemic and STZ/nicotinamide (NIC)-induced diabetic rats.

METHOD

after preparation of APLE, it was subjected to phytochemical screening, proximate composition and elemental assessments by using standard methods. Oral glucose tolerance test (OGTT) and maltose, lactose and sucrose oral challenge were assessed in normoglycemic rats post-APLE. Morphological characteristics of glucose response curve (time of glucose peak and shape of glucose response curve) were determined. Subsequently, diabetes mellitus was experimentally established in normoglycaemic adult Sprague-Dawley rats (weighing 150-250 g) of both sexes by sequential injection of Streptozotocin (STZ, 60 mg/kg ip)-reconstituted in sodium citrate buffer and NIC (110 mg/kg ip)-reconstituted in normal saline (1:1 v/v) for 16 weeks. Except control rats (normal saline 5 ml/kg ip; baseline fasting blood glucose [FBG] of 6.48 mmol/L), rats having FBG (stable at 11.1 mmol/L or ≥ 250 mg/dL) 3 days post-STZ/NIC injection were randomly re-assigned to one of the following groups: model (STZ/NIC-induced diabetic rats), APLE (100, 200 and 400 mg/kg respectively po) and metformin (300 mg/kg po) and treated daily for 28 days. Bodyweight and FBG were measured on weekly basis. FBG was measured by using standard glucometers. On day 28, rats were sacrificed under chloroform anesthesia, blood collected via cardiac puncture; kidney, liver and pancreas surgically harvested. While the pancreas was processed, sectioned and H&E-stained for histological examination, fresh kidney and liver were homogenized for assessment of total anti-oxidant capacity. Median cross-sectional area of pancreatic islets of Langerhans was determined for each group by using Amscope.

RESULTS

Cumulatively, APLE (100, 200 and 400 mg/kg respectively) dose-dependently decreased the initial FBG by 55.22, 76.15 and 77.77% respectively compared to model (-1.04%) and metformin (72.29%) groups. APLE treatment recovered damaged pancreatic β-cells and also increased median cross-sectional area (x10⁶ μm²) of pancreatic islets compared to that of model group. APLE significantly (P < 0.05) increased total anti-oxidant capacity (5.21 ± 0.02 AscAE μg/mL) of plasma, kidney and liver compared to model (4.06 ± 0.04 AscAE μg/mL) and metformin (4.87 ± 0.03 AscAE μg/mL) groups.

CONCLUSION

APLE has demonstrated glucose lowering and pancreato-protective effects in rats and arrested the characteristic loss in bodyweight associated with diabetes mellitus. This finding preliminarily confirms folk use of APLE as an anti-diabetic herbal medicine, whiles providing a rationale for further translational studies on APLE.

Total saponins extracted from Abrus cantoniensis Hance suppress hepatitis B virus replication in vitro and in rAAV8-1.3HBV transfected mice

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatitis B, an infectious disease caused by hepatitis B virus (HBV), is still a serious problem affecting global public health. Abrus cantoniensis Hance (AC), a traditional Chinese medicinal herb, has been used as a folk medicine for treating hepatitis in China from ancient times. However, its active ingredients are still unclear.

AIM OF STUDY

Our previous study indicated that saponins extracted from AC (ACS) were the active anti-HBV ingredients in AC. This study aimed to further investigate the anti-HBV effect of ACS in vitro and in vivo.

MATERIALS AND METHODS

HepG2.2.15 cells which consecutively produce HBV DNA and HBV antigens were used for in vitro test, and C57BL/6 mice infected by a recombinant adeno-associated virus 8 vector carrying 1.3 copies of HBV genome (rAAV8-HBV1.3) were used for in vivo test. The histopathological changes and the immune indices were evaluated in mice model. Genechip was conducted to identify genes and pathways regulated by ACS in HepG2.2.15 cells.

RESULTS

In this study, we confirmed that ACS treatment prominently inhibited production of HBV DNA, Hepatitis Be Antigen (HBeAg), and Hepatitis B surface antigen (HBsAg) in HepG2.2.15 cells. ACS treatment also decreased serum HBsAg, HBeAg, and HBV DNA level in rAAV8-1.3HBV transfected mice, which is in accordance with the in vitro results. Moreover, HBV infection-induced liver inflammation was significantly relieved by ACS, which could be observed in H&E staining and immunohistochemistry of HBcAg. ACS treatment elevated IFN-γ level in mice serum and increased CD4⁺ T cell percentage in splenocytes. KEGG pathway analysis showed that phenylalanine metabolism pathway and tyrosine metabolism pathway were greatly regulated by ACS treatment.

CONCLUSION

ACS exerted potent inhibitory effects on HBV replication both in vivo and in vitro, which may provide basis for its potential clinical usage.

Preventive Effects of Total Flavonoid C-Glycosides from Abrus mollis on Nonalcoholic Fatty Liver Disease through Activating the PPARα Signaling Pathway

Abrus pulchellus subsp. mollis (Hance) Verdc. (Leguminosae) is a well-known edible plant usually added to soups and beverages. In this study, vicenin-2 (1: ), isoschaftoside (2: ), schaftoside (3: ), and their enrichment fraction, total flavonoid C-glycosides, derived from the extracts of A. mollis, were firstly found to prevent nonalcoholic fatty liver disease both in vitro and in vivo. In the in vitro study, total flavonoid C-glycosides decreased the lipid accumulation in oleic acid-treated HepG2 cells. The mechanisms of total flavonoid C-glycosides are involved in the regulation of peroxisome proliferator-activated receptor α and its downstream, and the reduction of proinflammatory cytokines. In high-fat diet-induced fatty liver rats, total flavonoid C-glycosides decreased the levels of glutamic-oxalacetic transaminease and glutamic-pyruvic transaminase, and decreased the lipid accumulation both in the liver and blood without affecting food intake. In addition, total flavonoid C-glycosides also increased the activities of the antioxidant enzyme system in vivo. In conclusion, total flavonoid C-glycosides are active components of A. mollis on nonalcoholic fatty liver disease, and can be used in functional food and supplements for nonalcoholic fatty liver disease prevention and treatment.

Rapid detection of abrin in foods with an up-converting phosphor technology-based lateral flow assay

Abrin is a natural plant toxin found in the seeds of Abrus precatorius. It may be used for food poisoning or bioterrorism, seriously endangering public health. In this study, a reliable method for the rapid detection of abrin in foods was developed, based on an up-converting phosphor technology-based lateral flow assay (abrin-UPT-LFA). Nine high-affinity monoclonal antibodies (mAbs) against abrin were prepared, and the optimum mAbs (mAb-6F4 and mAb-10E11) were selected for use in the assay in double-antibody-sandwich mode. The assay was confirmed to be specific for abrin, with a detection sensitivity of 0.1 ng mL-1 for standard abrin solutions. Good linearity was observed for abrin quantitation from 0.1 to 1000 ng mL-1 (r = 0.9983). During the analysis of various abrin-spiked food samples, the assay showed strong sample tolerance and a satisfactory limit of detection for abrin (0.5-10 ng g-1 for solid and powdered samples; 0.30-0.43 ng mL-1 for liquid samples). The analysis of suspected food samples, from sample treatment to result feed-back, could be completed by non-professionals within 20 min. Therefore, the abrin-UPT-LFA is a rapid, sensitive, and reliable method for the on-site detection of abrin in foods.

[One new truxillic amide compound from Abrus mollis leaves]

The butanol extract part was extracted and isolated with water, alcohol and different organic solvents from Abrus mollis leaves. 6 compounds were isolated and purified using various column chromatographies and identified with the spectral techniques such as UV, MS, TLC, HPLC and NMR. The structures of 6 compounds were trigonelline (1), praline (2), alanine anhydride (3), (Z)-N-(4-hydroxycinnamoyl)tyrosine (4), (E)-N-(4-hydroxycinnamoyl)tyrosine (5), and abrusamide C (6). Compound 6 is a new compound, and compounds 1-4 were isolated from the plant for the first time.

Simultaneous Detection of Flavonoids, Phenolic Acids and Alkaloids in Abri Herba and Abri Mollis Herba using Liquid Chromatography Tandem Mass Spectrometry

INTRODUCTION

Abri Herba has remarkable properties, such as cleanup heat detoxification, dampness and activating blood circulation to dissipate blood stasis; as a result, it has been applied to treat acute or chronic hepatitis and mastitis. Abri mollis Herba is often used as Abri Herba. Hierarchical cluster analysis (HCA) was applied to compare the similarities and differences of the chemical compositions in the two types of medicinal materials.

OBJECTIVE

To establish a high-performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous analysis of 15 flavonoids, two phenolic acids and three alkaloids in Abri Herba and Abri mollis Herba.

METHODOLOGY

The chromatographic separation was performed on a C18 column with a mobile phase of methanol (A), acetonitrile (B) and 0.5‰ acetic acid in water (C) using gradient elution. The detection of the target compounds was performed in multiple-reaction monitoring (MRM) mode using a hybrid quadrupole linear ion trap mass spectrometer equipped with positive/negative ion-switching electrospray ionisation (ESI) source.

RESULTS

The developed method is reliable, sensitive and specific. In addition, the method has been successfully applied to differentiate 15 batches of Abri Herba and 27 batches of Abri mollis Herba stems. Furthermore, a comparison of the contents among stems, roots and leaves from the same strain in seven batches of Abri mollis Herba and four batches of Abri Herba has also been performed.

CONCLUSION

HPLC-MS/MS method is sensitive and selective and can be suitable for the reliable quality control of Abri mollis Herba and Abri Herba.

Antioxidative Activity of Flavonoids from Abrus cantoniensis against Ethanol-Induced Gastric Ulcer in Mice

The present study investigated the flavonoids from Abrus cantoniensis against ethanol-induced gastric ulcers in mice. The flavonoids from A. cantoniensis were extracted with ethanol and purified by macroporous resin and polyamide. The 2,2-diphenyl-1-picrylhydrazyl assay was used to measure the antioxidative activities in vitro. The ethanol-induced ulcer mouse model was used to evaluate the gastroprotective activities of the flavonoids from A. cantoniensis. In addition, a method was established to ensure accuracy for animal ulcer evaluation. The flavonoids from A. cantoniensis showed a strong free radical scavenging capacity with an IC50 of 43.83 µg/mL in the 2,2-diphenyl-1-picrylhydrazyl assay. At doses between 28.16-112.67 mg/kg, the flavonoids conspicuously reduced the ulcer index in ethanol-induced mice (p<0.001). Significant differences were found in the levels of superoxide dismutase, catalase, glutathione, and myeloperoxidase in the stomach tissues between the flavonoids from the A. cantoniensis groups and the ethanol control group. The gastroprotective effect of the flavonoids from A. cantoniensis could be due to its antioxidative activity of the defensive mechanism. The data revealed that the flavonoids from A. cantoniensis could be a potential therapeutic agent for gastric ulcer prevention and treatment.

Protective effect of total flavonoid C-glycosides from Abrus mollis extract on lipopolysaccharide-induced lipotoxicity in mice

Abrus mollis is a widely used traditional Chinese medicine for treating acute and chronic hepatitis, steatosis, and fibrosis. It was found that the total flavonoid C-glycosides from Abrus mollis extract (AME) showed potent antioxidant, anti-inflammatory, and hepatoprotective activities. To further investigate the hepatoprotective effect of AME and its possible mechanisms, lipopolysaccharide (LPS)-induced liver injury models were applied in the current study. The results indicated that AME significantly attenuated LPS-induced lipid accumulation in mouse primary hepatocytes as measured by triglyceride (TG) and total cholesterol (TC) assays and Oil Red O staining. Meanwhile, AME exerted a protective effect on LPS-induced liver injury as shown by decreased liver index, serum aminotransferase levels, and hepatic lipid accumulation. Real-time PCR and immunoblot data suggested that AME reversed the LPS-mediated lipid metabolism gene expression, such as sterol regulatory element-binding protein-1 (SREBP-1), fatty acid synthase (FAS), and acetyl-CoA carboxylase 1 (ACC1). In addition, LPS-induced overexpression of activating transcription factor 4 (ATF4), X-box-binding protein-1 (XBP-1), and C/EBP homologous protein (CHOP) were dramatically reversed by AME. Furthermore, AME also decreased the expression of LPS-enhanced interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2). Here, it is demonstrated for the first time that AME ameliorated LPS-induced hepatic lipid accumulation and that this effect of AME can be attributed to its modulation of hepatic de novo fatty acid synthesis. This study also suggested that the hepatoprotective effect of AME may be related to its down-regulation of unfolded protein response (UPR) activation.

[The establishment of a magnetic nanoparticle-based immunocapturing method for the detection of abrin]

OBJECTIVE

To develop a high sensitive and specific method for the detection of abrin.

METHODS

The abrin monoclonal antibody (mAb) 7D1 coated with Fe3O4 magnetic nanoparticles (MNPs) and abrin mAb labeled with horseradish peroxidase (HRP-mAb) were used to establish the immunocapturing method for abrin detection. The results were compared with the traditional double antibody sandwich ELISA.

RESULTS

The detecting linear of immunocapture for abrin was 2.5-60 ng/mL, and the linear regression equation was y=0.012x-0.015 with the detection limit of 2.5 ng/mL. Ricin at different concentrations did not interfere the abrin detection results, which demonstrated that the method had a good specificity . This approach showed good reproducibility with relative standard deviation ranging from 5.18%-8.67%. It could be used for analyzing abrin-contaminated specimens such as water, beverage, and milk, etc. The results of comparison with the conventional double antibody sandwich ELISA indicated that the immunocapture have a broader linear scale, higher sensitivity, and a shorter detection time.

CONCLUSION

The developed immunocapturing method can be used for detecting traces of abrin.

α-Amylase inhibitory triterpene from Abrus precatorius leaves

In the screening experiments for porcine pancreatic α-amylase inhibitors in 18 plants obtained from Indonesia, a potent inhibitory activity was detected in the extract of leaves of Abrus precatorius. The enzyme assay-guided fractionation of the extract led to the isolation of a triterpene ketone, lupenone (1), as a potent α-amylase inhibitor, together with 24-methylenecycloartenone (2) and luteolin (3). The mode of inhibition of compound 1 against porcine pancreatic α-amylase was a mixed inhibition. This is the first report that describes the potent α-amylase inhibitory activity of the low-polar triterpene ketone similar to compound 1. A comparison of the activities of the isolate and related compounds indicated the importance of C-3 ketone and the lupane skeleton in the α-amylase inhibitory activity.

Antiprotozoal isoflavan quinones from Abrus precatorius ssp. africanus

A library of 206 extracts from selected South African plants was screened in vitro against a panel of protozoan parasites, Plasmodium falciparum, Trypanosoma brucei rhodesiense, and Leishmania donovani. A CH2Cl2/MeOH (1 : 1) extract of Abrus precatorius L. ssp. africanus strongly inhibited P. falciparum (98 %), T. b. rhodesiense (100 %), and L. donovani (76 %) when tested at a concentration of 10.0 µg/mL. The active constituents were tracked by HPLC-based activity profiling and isolated by preparative and semipreparative RP-HPLC chromatography. Structures were established by HR-ESIMS, and 1D and 2D NMR (1H, 13C, COSY, HMBC, HSQC, and NOE difference spectroscopy). Five compounds were obtained and identified as two isoflavan hydroquinones, abruquinone H (1) and abruquinone G (2), and three isoflavan quinones, abruquinone I (3), abruquinone B (4), and 7,8,3''5'-tetramethoxyisoflavan-1',4'-quinone (5). Compounds 1 and 3 were new natural products. The absolute configuration of compounds was determined by comparison of electronic circular dichroism spectra with calculated ECD data. Compounds 3 and 4 showed strong activity against T. b. rhodesiense (IC50 values of 0.30 and 0.16 µM, respectively) and good selectivity (selectivity indices of 73.7 and 50.5, respectively).

Abrin immunotoxin: targeted cytotoxicity and intracellular trafficking pathway

BACKGROUND

Immunotherapy is fast emerging as one of the leading modes of treatment of cancer, in combination with chemotherapy and radiation. Use of immunotoxins, proteins bearing a cell-surface receptor-specific antibody conjugated to a toxin, enhances the efficacy of cancer treatment. The toxin Abrin, isolated from the Abrus precatorius plant, is a type II ribosome inactivating protein, has a catalytic efficiency higher than any other toxin belonging to this class of proteins but has not been exploited much for use in targeted therapy.

METHODS

Protein synthesis assay using (3)[H] L-leucine incorporation; construction and purification of immunotoxin; study of cell death using flow cytometry; confocal scanning microscopy and sub-cellular fractionation with immunoblot analysis of localization of proteins.

RESULTS

We used the recombinant A chain of abrin to conjugate to antibodies raised against the human gonadotropin releasing hormone receptor. The conjugate inhibited protein synthesis and also induced cell death specifically in cells expressing the receptor. The conjugate exhibited differences in the kinetics of inhibition of protein synthesis, in comparison to abrin, and this was attributed to differences in internalization and trafficking of the conjugate within the cells. Moreover, observations of sequestration of the A chain into the nucleus of cells treated with abrin but not in cells treated with the conjugate reveal a novel pathway for the movement of the conjugate in the cells.

CONCLUSIONS

This is one of the first reports on nuclear localization of abrin, a type II RIP. The immunotoxin mAb F1G4-rABRa-A, generated in our laboratory, inhibits protein synthesis specifically on cells expressing the gonadotropin releasing hormone receptor and the pathway of internalization of the protein is distinct from that seen for abrin.

Antioxidant and antiproliferative activities of Abrus precatorius leaf extracts--an in vitro study

BACKGROUND

The use of traditional medicine at the primary health care level is widespread and plant-based treatments are being recommended for curing various diseases by traditional medical practitioners all over the world. The phytochemicals present in the fruits, vegetables and medicinal plants are getting attention day-by-day for their active role in the prevention of several human diseases. Abrus precatorius is a widely distributed tropical medicinal plant with several therapeutic properties. Therefore in the present study, A. precatorius leaf extracts were examined for their antioxidant and cytotoxic properties in vitro in order to discover resources for new lead structures or to improve the traditional medicine.

METHODS

In this study, antioxidant and antiproliferative properties of the different leaf extracts (hexane, ethyl acetate, ethanol and water) from A. precatorius were investigated along with the quantification of the polyphenol and flavonoid contents. The ability of deactivating free radicals was extensively investigated with in vitro biochemical methods like DPPH(∙), (∙)OH, NO, SO(2-) scavenging assays and inhibition capability of Fe(II)-induced lipid peroxidation. Furthermore, antiproliferative activities using different human cancer cell lines and primary cell line was carried out by MTT method.

RESULTS

Total phenolic content and total flavonoid content of the extracts were found in the range of 1.65 ± 0.22 to 25.48 ± 0.62 GAE mg/g dw and 6.20 ± 0.41 to 17.16 ± 1.04 QE mg/g dw respectively. The experimental results further revealed that A. precatorius extracts showed strong antiradical properties, capable to chelate Fe(2+) and possess good inhibition ability of lipid peroxidation. In addition, as a first step towards the identification of phytoconstituents endowed with potent chemopreventive activities, we evaluated the inhibitory effects of A. precatorius extracts on the proliferation of four different human tumour cell lines such as human colon adenocarcinoma cells (Colo-205), human retinoblastoma cancer cells (Y79), human hepatocellular carcinoma cells (HepG2) and Leukemia cells (SupT1). Ethanol extract (APA) and ethyl acetate extract (APE) of A. precatorius had apparent capabilities of inhibiting the survival of tested human cancer cell lines. Moreover, it was observed that the A. precatorius extracts did not inhibit the growth of mice peritoneal macrophages, thus confirming that plants extracts are selective against the cancer cell lines.

CONCLUSION

This work provides a scientific support for the high antioxidant and antiproliferative activity of this plant and thus it may find potential applications in the treatment of the diseases caused by ROS. Further studies are needed to confirm in vivo anti-tumorgenicity and subsequent chemical characterization of the active molecule(s).

[Experimental research on prevention and treatment of fatty liver rats with Abrus cantoniensis]

OBJECTIVE

To investigate the effects of Abrus cantoniensis (AC) on blood lipid metabolism, pathomorphological change of the liver and fenestrae of liver sinus endothelial cell (LSEC) in fatty liver disease rats.

METHODS

SD rats were divided into 7 groups: blank control group,fatty liver model group, simvastatin group (7.2 mg/kg), Gynostemma pentaphyllum group (16.2 mg/kg), high dose (40 g/kg), middle dose (20 g/kg) and low dose (10 g/kg) of AC groups. All rats except blank control group were fed with high fat diet for the first 3 weeks, then treated with different conditions as previously mentioned for the next 3 weeks while keep on feeding with high fat diet. At the 43rd day,the abdominal aortic blood was collected for measuring the serum concentration of AST, ALT, TC, TG, HDL-C, LDL-C, and liver tissues were taken to make pathological sections for observation by optical microscope or were prepared for scanning electronic microscope.

RESULTS

The levels of AST, ALT, TC, TG, LDL-C were obviously decreased while HDL-C were increased in fatty liver rats by AC high dose. Meanwhile the cell morphology of liver tissues and the fenestraes of LSEC were improved as well.

CONCLUSION

AC can ameliorate the levels of blood lipid in fatty liver rats and improve the pathological change of liver tissues. To some extent AC has the function of prevention and treatment of fatty liver.

A new triterpenoid saponin from Abrus precatorius Linn

A new triterpenoid saponin, 3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl subprogenin D (1), together with six known triterpenoids: subprogenin D (2), abrusgenic acid (3), triptotriterpenic acid B (4), abruslactone A (5), abrusogenin (6) and abrusoside C (7) were isolated from the leaves and stems of Abrus precatorius. Their structures were elucidated on the basis of physical and NMR analysis, respectively. Compounds 5 and 6 showed moderate cytotoxicity against MCF-7, SW1990, Hela, and Du-145 cell lines. Compounds 1, 2 and 4 were isolated from this plant for the first time.

Antiparasitic and antimicrobial isoflavanquinones from Abrus schimperi

The EtOH extract of Abrus schimperi (Fabaceae), collected in Kenya, demonstrated significant activity against Leishmania donovani promastigotes with IC50 value of 3.6 microg/mL. Bioassay-guided fractionation of CHCl3 fraction using Centrifugal Preparative TLC afforded two antiparasitic isoflavanquinones, namely amorphaquinone (1) and pendulone (2). They displayed IC50 values of 0.63 microg/mL and 0.43 microg/mL, respectively, against L. donovani promastigotes. Both the compounds were also evaluated against L. donovani axenic amastigotes and amastigotes in THPI macrophage cultures. In addition, compounds 1 and 2 showed antiplasmodial activity against Plasmodium falciparum D6 and W2 strains, while 2 displayed antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (each IC50 1.44 microg/mL). The 1H and 13C data of 1, not fully assigned previously, were unambiguously assigned using 1D and 2D NMR HMBC and HMQC experiments. In addition, the absolute stereochemistry of the isolated compounds 1 and 2 was revised as C-(3S) based on Circular Dichroism experiments. This appears to be the first report of amorphaquinone (1) and pendulone (2) from the genus Abrus.

Attempted suicide, by mail order: Abrus precatorius

OBJECTIVE

Abrus precatorius is cultivated in many subtropical areas. The seeds exist in a variety of colors such as black, orange, and most commonly, glossy red. A black band is found at the end of the seed. The plant contains multiple pods which typically contain three to five Abrus seeds. The seeds contain abrin, which inhibits ribosomal function, halting protein synthesis and leading to cellular death. A unique aspect of this case is the use of the internet to order a potentially lethal poison as well as transmission of a picture to identify the seed.

CASE REPORT

A 20-year-old man presented to the emergency department complaining of vomiting and watery diarrhea for 6-8 h prior to arrival. He denied any medication use, recent illness, travel, or changes in his diet. Initial vital signs were normal. The patient was diagnosed with viral gastroenteritis. During his evaluation, the patient admitted to feeling suicidal. While awaiting psychiatry evaluation, the patient's father arrived with a box of small hard red seeds, which he believed that his son ingested in a suicide attempt. The seeds could not be identified by the staff. A picture of the seeds was transmitted by e-mail to the New York City Poison Control Center, allowing their identification as A. precatorius. The patient was reinterviewed and admitted to chewing and swallowing 10 seeds. Given the potential toxicity of abrin, the patient was admitted to the intensive care unit. He continued to have frequent episodes of emesis as well as diarrhea. He gradually improved over 2 days. He admitted to ordering a box of Abrus seeds online from Asia after reading on the Internet about their use in suicide. He was eventually discharged for outpatient follow-up with no permanent sequelae.

CONCLUSION

Abrin has an estimated human fatal dose of 0.1-1 μg/kg. Most cases of Abrus seed ingestions are unintentional and occur in children. Ingesting the intact seeds typically results in no clinical findings, as they pass through the gastrointestinal tract due to their hard shell. Abrin released during chewing is poorly absorbed systemically from the gastrointestinal tract. This causes the vomiting and diarrhea with resultant hypovolemia and electrolyte disturbances, which can be severe and life threatening, particularly in areas with less advanced health care systems. Management is primarily supportive.

[Origins determination of Herba Abri cantoniensis and Herba Abri mollis with FTIR combined with fuzzy cluster and curve-fitting]

The methods of fuzzy cluster and curve-fitting combined with FTIR were used to determine the origins of Herba Abri cantoniensis and Herba Abri mollis. The spectra of Herba Abri cantoniensis and Herba Abri mollis are similar, both with typical spectral shapes. The two spectra can be divided into 3 parts: the 1st is 3 500-2 800 cm(-1), containing stretching bands of -OH, N-H, and CH2 ; the 2nd is 1 800-800 cm(-1), containing stretching bands of ester carbonyl group and indican C-O(H), vibrational bands of C=C and benzene ring; The 3rd is 800-400 cm(-1), containing skeletal vibration and scissoring vibration of molecular. The recorded FTIR spectral data were processed by 9-point-smoothing, 1st derivative, SNV and fuzzy cluster analysis sequentially. The fuzzy cluster analysis was carried out by similarity or dissimilarity matrix, and two matrices are computed with Manhattan and Euclidean distance. The results indicated that the optimization used Manhattan and dissimilarity matrix, and 5 origins of Herba Abri cantoniensis were perfectly discriminated, but 2 origins of Herba Abri mollis were mixed and identified from the other 3 origins. So the characterized bands at 1 034 cm(-1) of the average 1-D spectra of Herba Abri cantoniensis and Herba Abri mollis were fitted combining 2nd derivative for further distinguishing their spectral characteristic. The results of curve-fitting showed that the bands of wild Herba Abri cantoniensis and the other origin ones were decomposed to 11 and 9 component bands respectively, but the bands of Shanglin and the other origins Herba Abri mollis were decomposed to 9 and 8 component bands dissimilarly, and the locations and normalized densities of these component bands were different. From this, together with the results of fuzzy cluster analysis, it is concluded that the combination of two methods may identify the origins of Herba Abri cantoniensis and Herba Abri mollis availably.

[Comparative study on the infrared fingerprint of Abrus cantoniensis based on the methods of sequential analysis of dual-indexes and cluster analysis]

The methods of sequential analysis of dual-indexes and cluster analysis were utilized to investigate the infrared fingerprints of A. cantoniensis planted in different years and different places in Guangxi, China. The results showed that 6 samples were able to be completely separated only through 13 point smoothing, when the dual-indexes analysis was applied in the present research, and the accurate relationship between these samples could be inspected and expressed by quantitative relationships under 6-dimensional spaces; however, the effect of cluster was bad only through 13 point smoothing of raw spectra, and it was very difficult to find out the regular sequences while the cluster analysis was applied. Furthermore, the 6 samples were able to be completely separated if raw spectra were dealed with 1st derivative after 13 point smoothing, and the clustering effects were more obvious and 6 samples of A. cantoniensis were completely separated. The above two methods could be used to evaluate the quality of Chinese medicinal materials easily when the sample was not excessive quantitatively, but the method of dual-indexes analysis was more difficult than the clustering analysis if the sample size was too large, since a mass of data such as common peak ratio and variation peak ratio of the IR fingerprint spectra were processed and analyzed statistically, while this method could accurately find out the closest relationship between any samples through comparing the quantitative relationships of common peak ratio and variation peak ratio of each sample under 6-dimensional space; the precision of cluster analysis was less than dual-indexes analysis, but it was more convenient than dual-indexes analysis when large sample data were analysed. Finally the above two methods all showed that the chemical composition of the A. cantoniensis was similar in the same cultivated area, but the difference in chemical composition of A. cantoniensis in different years was distinct even they were in the same place.

In vitro immunostimulatory properties of Abrus lectins derived peptides in tumor bearing mice

In vitro immunostimulatory effect of Abrus lectins derived peptide fractions (AGP and ABP) was investigated in DL bearing mice. Both AGP and ABP were found to activate splenocytes and induced production of cytokines like IL-2, IFN-gamma and TNF-alpha indicating a Th1 type of immune response. Analysis of in vitro treated splenocytes by flow cytometry revealed an increase in percentage of T and B cell with high expression of activation markers (CD25(+) and CD71(+)). At the same time, expression of co-stimulatory markers was significantly high compared to tumor control. The tumor associated macrophages were able to stimulate NO production, IL-1 secretion, increased phagocytosis and decreased expression of mannose receptor. It was also observed that NK cell was activated by AGP and ABP. These results suggest that both AGP and ABP act as immunostimulants in vitro in DL bearing mice.

Effect of Abrin on Cell-Mediated Immune Responses in Mice

Effect of abrin isolated from Abrus precatorius on the cellular immune responses was studied in normal as well as tumor-bearing animals. Administration of abrin was found to enhance the proliferation of splenocytes and thymocytes (lymphocytes in general) in responses to mitogens. Natural killer cell activity was enhanced significantly by abrin in both the normal (49.8% cell lysis on day 9) and the tumor-bearing group (51.7% cell lysis on day 9), and it was found to be earlier than the control. Antibody dependent cellular cytotoxicity was enhanced in the abrin treated tumor-bearing group on the ninth day (44% cell lysis). An early antibody dependent complement mediated cytotoxicity was observed in the abrin treated group on day 15 (27.6% cell lysis). Results of our present study suggest the immunomodulatory property of abrin.

Effects of native and heat-denatured Abrus agglutinin on tumor-associated macrophages in Dalton's lymphoma mice

Tumor-associated macrophages (TAMs) have a complex and ambivalent relationship with tumor progression and elimination. Though TAMs are reported to have pro- and anti-tumor roles, upon modification and activation TAMs can develop tumoricidal activities and thus might have applications in cancer therapy. Various immunomodulatory compounds could be used to modulate TAMs. In this study we used Abrus agglutinin, a plant lectin, in its native and heat-denatured forms, to investigate its effect on TAMs in Dalton's lymphoma-bearing mice. We found that treatment with both native (NA) and heat-denatured agglutinin (HDA) activated the TAMs, which showed significantly increased in vitro cytotoxicity towards tumor cells and production of nitric oxide but no difference in TNF-alpha production. The tumoricidal activities of both NA and HDA were dependent upon the activation of TAMs as in macrophage-depleted Dalton's lymphoma-bearing mice NA and HDA treatment could not decrease the number of tumor cells significantly. Thus, NA and HDA could be used as modulators of TAMs, for their therapeutic use in cancer.

Activity-directed-fractionation and isolation of four antibacterial compounds from Abrus precatorius L., roots

Root extracts of the plant Abrus precatorius L., was tested for antibacterial activity. Various solvent fractions exhibited inhibitory activity against 13 gram-positive and gram-negative bacteria. Root extracts were analyzed by thin layer chromatography (TLC). The antibacterial activity was localized to specific chromatophores in the chloroform fraction through a bioautography assay. It was found localized to four chromatophores out of seven. The chromatophores were isolated from the TLC plates and rechecked for activity against Slaphylococcus aureus A, using a disc diffusion assay. Among the four active principles isolated, AP 3 (Rf 0.87) exhibited maximum activity i.e. 56% inhibition of growth of S. aureus A, in disc diffusion assay compared to the standard antibiotic Ampicillin. Results of this study suggest that chloroform extractable phytochemicals in A. precatorius L. may yield promising molecules with antibiotic activity.

Studies on the toxicity of an aqueous extract of the leaves of Abrus precatorius in rats

The toxic effects of an aqueous extract of Abrus precatorius were studied in 20 male white rats over a period of 18 days. The rats were divided into four groups of five rats per group. Those in Group A served as controls while the rats in Groups B, C and D were dosed per os with 400 mg/kg, 800 mg/kg and 1 600 mg/kg of the extract, respectively. Blood samples were collected for haematological and biochemical analysis and specimens of the liver, kidney and testes were taken for histopathological studies. The study showed that the extract of A. precatorius caused decreased levels of packed cell volume, haemoglobin concentration, red blood cell count, white blood cell count, mean corpuscular volume and mean corpuscular haemoglobin. The extract also resulted in increased levels of total serum protein, albumin, alanine amino transaminase, aspartate amino transferase, alkaline phosphatase and total bilirubin. Histologically, testicular degeneration characterized by decreased numbers of lining cells of the epithelium as well as reduction in sperm cells with presence of scattered Sertoli cells were noted. The study thus showed that aqueous extract of Abrus precatorius is toxic and caution should be exercised in its use for medicinal purpose.

Polysaccharide structure of degraded glucomannan from Abrus precatorius Linn. seeds

Degraded glucomannan was isolated from Abrus precatorius Linn. seed polysaccharide (Papilionaceae). Acid hydrolysis and methylation studies produced certain degraded methyl sugars as, 2, 3, 6-tri-O-methyl-D-glucose and 2, 3, 6-tri-O-methyl-D-mannose in 1:4 molar ratio. On the basis of hydrolysis and methylation experiments, a polysaccharide structure has been assigned to the degraded glucomannan and to the parent glucomannan of Abrus precatorius Linn. seed.

Structure-Function Analysis and Insights into the Reduced Toxicity of Abrus precatorius Agglutinin I in Relation to Abrin

Abrin and agglutinin-I from the seeds of Abrus precatorius are type II ribosome-inactivating proteins that inhibit protein synthesis in eukaryotic cells. The two toxins share a high degree of sequence similarity; however, agglutinin-I is weaker in its activity. We compared the kinetics of protein synthesis inhibition by abrin and agglutinin-I in two different cell lines and found that approximately 200-2000-fold higher concentration of agglutinin-I is needed for the same degree of inhibition. Like abrin, agglutinin-I also induced apoptosis in the cells by triggering the intrinsic mitochondrial pathway, although at higher concentrations as compared with abrin. The reason for the decreased toxicity of agglutinin-I became apparent on the analysis of the crystal structure of agglutinin-I obtained by us in comparison with that of the reported structure of abrin. The overall protein folding of agglutinin-I is similar to that of abrin-a with a single disulfide bond holding the toxic A subunit and the lectin-like B-subunit together, constituting a heterodimer. However, there are significant differences in the secondary structural elements, mostly in the A chain. The substitution of Asn-200 in abrin-a with Pro-199 in agglutinin-I seems to be a major cause for the decreased toxicity of agglutinin-I. This perhaps is not a consequence of any kink formation by a proline residue in the helical segment, as reported by others earlier, but due to fewer interactions that proline can possibly have with the bound substrate.

[Determination of total flavonoids in Abrus cantoniensis and its dynamic changes]

OBJECTIVE

To develop a method for ultrasonic extraction and determination of total flavonoids in Abrus cantoniensis, and to analyze its dynamic changes.

METHOD

The optimized condition of extraction of total flavonoids was studied with orthogonal design. The contents of total flavonoids in different organs and of different growth stages were determined by UV-visible spectrophotometer.

RESULT

The ethanol volume and extraction times were the main factors impacting the effects of ultrasonic extraction. The content of total flavonoids in stems were higher than in roots and the lowest in leaves. The dynamic changes of total flavonoids contents in roots and stems of A. cantoniensis were in similar trends. Its total flavonoids content in the two parts of plant increased gradually with the growth and reached the maximum in October, and the content decreased significantly in Feburay of next year. The content of total flavonoids in leaves reached also to the highest value before leaves fell off.

CONCLUSION

The optimized extraction method of total flavonoids in Abrus contoniensis was obtained with three times with 80% ethanol at 20 times of volume for 30 min. The results implied that the best yield and quality may be obtained before leaves fall.

Pulchellin, a highly toxic type 2 ribosome-inactivating protein from Abrus pulchellus. Cloning heterologous expression of A-chain and structural studies

Pulchellin is a type 2 ribosome-inactivating protein isolated from seeds of the Abrus pulchellus tenuiflorus plant. This study aims to obtain active and homogeneous protein for structural and biological studies that will clarify the functional aspects of this toxin. The DNA fragment encoding pulchellin A-chain was cloned and inserted into pGEX-5X to express the recombinant pulchellin A-chain (rPAC) as a fusion protein in Escherichia coli. The deduced amino acid sequence analyses of the rPAC presented a high sequential identity (> 86%) with the A-chain of abrin-c. The ability of the rPAC to depurinate rRNA in yeast ribosome was also demonstrated in vitro. In order to validate the toxic activity we promoted the in vitro association of the rPAC with the recombinant pulchellin binding chain (rPBC). Both chains were incubated in the presence of a reduced/oxidized system, yielding an active heterodimer (rPAB). The rPAB showed an apparent molecular mass of approximately 60 kDa, similar to the native pulchellin. The toxic activities of the rPAB and native pulchellin were compared by intraperitoneal injection of different dilutions into mice. The rPAB was able to kill 50% of the tested mice with doses of 45 microg x kg(-1). Our results indicated that the heterodimer showed toxic activity and a conformational pattern similar to pulchellin. In addition, rPAC produced in this heterologous system might be useful for the preparation of immunoconjugates with potential as a therapeutic agent.

A rapid densitometric method for simultaneous quantification of gallic acid and ellagic acid in herbal raw materials using HPTLC

Gallic acid and ellagic acid are two widely occurring phenolic compounds of plant origin, to which many biological activities including anticancer and antiviral activity have been attributed. A simple HPTLC method has been developed for the simultaneous quantification of gallic acid and ellagic acid. The method was validated for precision, repeatability, and accuracy. Instrumental precision was found to be 0.083 and 0.78, and the repeatability of the method was found to be 1.07 and 1.50 (% CV) for gallic acid and ellagic acid, respectively. The accuracy of the method was checked by a recovery study conducted at two different levels and the average percentage recovery was found to be 101.02% for gallic acid and 102.42% for ellagic acid. The above method was used for the quantification of gallic acid and ellagic acid content in seeds of Abrus precatorius Linn., whole plant of Phyllanthus maderaspatensis Linn., and flowers of Nymphaea alba Linn. The proposed HPTLC method for the simultaneous quantification of gallic acid and ellagic acid was found to be simple, precise, specific, sensitive, and accurate and can be used for routine quality control of herbal raw materials and for the quantification of these compounds in plant materials.

Immunomodulatory role of native and heat denatured agglutinin from Abrus precatorius

Lectins are known as polyclonal activators of lymphocytes and work through the induction of battery of cytokines, which vary from lectin to lectin. Most widely used biological response modifier Mistletoe lectin (ML-1) in therapy stimulates lymphocytes, macrophages, and natural killer cells and induces both TH1 and TH2 type cytokines. Abrus agglutinin, similar to ML-1 with respect to carbohydrate specificity [gal (beta1-->3) gal/Nac], was studied both in native (NA) and heat denatured (HDA) condition for murine splenocyte proliferation, cytokine secretion, NK-cell activation, and thymocyte proliferation in vitro with a view to assess its potential as an immunomodulator. Both NA and HDA activate splenocytes and induce production of cytokines like IL-2, IFN-gamma and TNF-alphabeta indicating a TH1 type of immune response. Native agglutinin and HDA induced conditioned media of adherent splenocytes could stimulate non-adherent splenocytes and vice versa. Heat denatured agglutinin was able to induce NK-cell activation at much lower concentration than that of NA, but the extent of NK-cell activation was higher for NA. Proliferation of thymocytes by NA and HDA was also observed. This study indicates that Abrus agglutinin could be a potential immunomodulator both in native as well as in heat denatured form.

Plant-derived abrin-a induces apoptosis in cultured leukemic cell lines by different mechanisms

Abrin-a consists of A-chain with N-glycosidase activity, which inhibits protein synthesis, and lectin-like B-chain responsible for binding with cell-surface receptors and penetrating of abrin-a molecule into the cells. As a lectin component, the B-chain can also participate in cell signal transduction. It has been reported that abrin induces apoptosis, but the molecular mechanism(s) of this induction have been obscure and several alternative variants have been discussed. The present study demonstrates that abrin-a induces apoptosis in human cultured cell lines, derived from acute lymphoblastic leukemia (ALL) (Jurkat, CCRF-CEM, MOLT-4, HPB-ALL). The apoptosis was estimated by: phosphatidylserine (PSer) exposure at the cell surface, activation of caspase cascade, and DNA fragmentation. The penetrating of abrin-a into the cells was detected by fluorescent confocal microscopy, using fluorescein isothiocyanate (FITC) as a fluorescent marker. It was established that the effect of abrin-a on the apoptosis induction in leukemic cells was dose- and time-dependent. The process was initiated 1 h after abrin-a application (before its penetrating into the cells) and was characterized with PSer translocation from the inner to the outer monolayer of plasma membrane, caspase activation on the first to second hour after beginning of treatment, with maximum on the third to fourth hour, and DNA fragmentation on the fourth to sixth hour, depending of the cell line. The exposure of PSer on the cell surface was detected in Jurkat, CCRF-CEM, and MOLT-4 cells. In HPB-ALL, no significant changes in PSer exposure on the cell surface was observed. Activation of caspase-3, -8, and -9 was detected in Jurkat, MOLT-4, and HPB-ALL. Surprisingly, the activity of caspase-3 increased on the first hour after beginning of treatment, while the activity of caspase-8 and -9 began to increase on the second hour. In CCRF-CEM, activation of caspases was not measured, but the apoptosis progressed to DNA fragmentation in a dose- and time-dependent manner. DNA fragmentation was also detected in Jurkat, but not in MOLT-4 and HPB-ALL cells. It seems that the mechanisms of abrin-a-induced apoptosis are different and the progress of apoptosis depends of the cell line. There was a very good positive correlation between the agglutinating activity of abrin-a and development of apoptosis to DNA fragmentation. The time-dependent effects of abrin-a on apoptosis as well as its time-dependent penetration into the cells suggest that the B-chain probably triggers the apoptosis, while the A-chain and breakage of the disulfide bond are responsible for its progress.

Stimulation of murine macrophages by native and heat-denatured lectin from Abrus precatorius

We have evaluated the immunostimulant activity of native agglutinin (NA) and heat-denatured agglutinin (HDA) obtained from Abrus precatorius seed kernels on murine macrophages. Activated macrophages play an important role in nonspecific immunostimulation in turn by activating the other immune cells in the cascade. Significant alterations are observed in the macrophage functions both by native and heat-denatured Abrus agglutinin. Increased production of nitric oxide and hydrogen peroxide and a high phagocytic and bactericidal activity is potentiated by both NA and HDA. It is also observed that activated macrophages also released interleukin-1. These results suggest that both NA and HDA act as immunostimulants in vitro.

New triterpenoids from the leaves of Abrus precatorius

Three new (1-3) triterpenoids and one known (4) triterpenoid were isolated from an acid hydrolyzed methanol-soluble extract of the leaves of Abrus precatorius. Their structures were identified as (20S,22S)-3beta,22-dihydroxycucurbita-5(10),24-diene-26,29-dioic acid delta-lactone (1), 3-O-[6'-methyl-beta-D-glucuronopyranosyl]-3beta,22beta-dihydroxyolean-12-en-29-oic acid methyl ester (2), 3-O-beta-D-glucuronopyranosylsophoradiol methyl ester (3), and sophoradiol (4) by spectroscopic techniques including 2D NMR.

Immunopotentiating activity of abrin, a lectin from Abrus precatorius Linn

A non-toxic dose of abrin, (1.25 microg/kg body wt) consecutively for five days in normal mice stimulated specific humoral responses. A noticeable increase was observed in total leucocyte count, lymphocytosis, weights of spleen and thymus, circulating antibody titre, antibody forming cells, bone marrow cellularity and alpha-esterase positive bone marrow cells. The results suggest that abrin can potentiate the humoral immune response of the host.

A new biologically active flavonol glycoside from the seeds of Abrus precatorius Linn

A new flavonol glycoside m.f. C29H34O16, m.p. 260-262 degrees C, [M]+ 638 (EIMS) was separated from the chloroform soluble fraction of the concentrated 80% methanolic extract of the seeds of Abrus precatorius (Linn). It was characterised as a new biologically active flavonol glycoside 7,3',5'-trimethoxy-4'-hydroxy flavone-3-O-beta-D-galactosyl-(l --> 4)-alpha-L-xyloside (1) by several colour reactions, spectral analysis and chemical degradations.

Characterization of the sugar-binding specificity of the toxic lectins isolated from Abrus pulchellus seeds

The sugar-binding specificity of the toxic lectins from Abrus pulchellus seeds was investigated by combination of affinity chromatography of glycopeptides and oligosaccharides of well-defined structures on a lectin-Sepharose column and measurement of the kinetic interactions in real time towards immobilized glycoproteins. The lectins showed strong affinity for a series of bi- and triantennary N-acetyllactosamine type glycans. The related asialo-oligosaccharides interact more strongly with the lectins. The best recognized structures were asialo-glycopeptides from fetuin. Accordingly, the kinetic interaction with immobilized asialofetuin was by far the most pronounced. Human and bovine lactotransferrins and human serotransferrin interacted to a lesser extent. The interaction with asialofetuin was inhibited by galactose in a dose dependent manner. Lactose, N-acetyllactosamine and lacto-N-biose exhibited similar degree of inhibition while N-acetylgalactosamine was a poor inhibitor. These results suggested that the carbohydrate-binding site of the Abrus pulchellus lectins was specific for galactose and possess a remarkable affinity for the sequences lactose [beta-D-Gal-(1-->4)-D-Glc], N-acetyllactosamine [beta-D-Gal-(1-->4)-D-GlcNAc] and lacto-N-biose [beta-D-Gal-(1-->3)-D-GlcNAc].