Nutritional evaluation of kidney beans (Phaseolus vulgaris): chemical composition, lectin content and nutritional value of selected cultivars

Exploitation of Common Bean Flours with Low Antinutrient Content for Making Nutritionally Enhanced Biscuits

Consumption of legumes is associated with a number of physiological and health benefits. Legume proteins complement very well those of cereals and are often used to produce gluten-free products. However, legume seeds often contain antinutritional compounds, such as phytate, galactooligosaccharides, phenolic compounds, lectins, enzyme inhibitors, whose presence could affect their nutritional value. Screening natural and induced biodiversity for useful traits, followed by breeding, is a way to remove undesirable components. We used the common bean cv. Lady Joy and the lpa1 mutant line, having different seed composition for absence/presence of lectins,α-amylase inhibitor, (α-AI) and phytic acid, to verify the advantage of their use to make biscuits with improved nutritional properties. We showed that use of unprocessed flour from normal beans (Taylor's Horticulture and Billò) must be avoided, since lectin activity is still present after baking, and demonstrated the advantage of using the cv. Lady Joy, lacking active lectins and having active α-AI. To assess the contribution of bean flour to biscuit quality traits, different formulations of composite flours (B12, B14, B22, B24, B29) were used in combinations with wheat (B14), maize (gluten-free B22 and B29), or with both (B12 and B24). These biscuits were nutritionally better than the control, having a better amino acid score, higher fiber amount, lower predicted glycemic index (pGI) and starch content. Replacement of cv. Lady Joy bean flour with that of lpa1, having a 90% reduction of phytic acid and devoid of α-AI, contributed to about a 50% reduction of phytic acid content. We also showed that baking did not fully inactivate α-AI, further contributing to lowering the pGI of the biscuits. Finally, data from a blind taste test using consumers indicated that the B14 biscuit was accepted by consumers and comparable in terms of liking to the control biscuit, although the acceptability of these products decreased with the increase of bean content. The B22 gluten-free biscuits, although received liking scores that were just above the middle point of the hedonic scale, might represent a good compromise between health benefits (absence of gluten and lower pGI), expectations of celiac consumers and likeness.

Effect of White Kidney Beans (Phaseolus vulgaris L. var. Beldia) on Small Intestine Morphology and Function in Wistar Rats

The chronic ingestion of raw or undercooked kidney beans (Phaseolus vulgaris L.) causes functional and morphological derangement in various tissues. The major objectives of this study were to investigate the gavage effects of a raw Beldia bean variety that is widely consumed in Tunisia, on the small intestine morphology and jejunal absorption of water, electrolytes, and glucose in Wistar rats. Twenty young male rats were randomly divided into two groups of 10 rats. The first group served as the control and was gavaged with 300 mg of a rodent pellet flour suspension (RPFS), whereas the second experimental group was challenged with 300 mg of a Beldia bean flour suspension (BBFS) for 10 days. Histological studies were performed using light and electron microcopy. The intestinal transport of water, sodium, potassium, and glucose was studied by perfusing the jejunal loops of the small bowels in vivo. The feeding experiments indicated that BBFS did not affect weight gain. Histomorphometric analyses showed that the villus heights, crypt depths, and crypt/villus ratios in the jejunum and ileum were greater in the BBFS-fed rats than controls. Electron microscopy studies demonstrated that the rats exposed to RPFS exhibited intact intestinal tracts; however, the BBFS-treated rats demonstrated intestinal alterations characterized by abnormal microvillus architectures, with short and dense or long and slender features, in addition to the sparse presence of vesicles near the brush border membrane. BBFS administration did not significantly affect glucose absorption. However, significant decreases were observed in water and electrolyte absorption compared with the uptake of the controls. In conclusion, raw Beldia beans distorted jejunum morphology and disturbed hydroelectrolytic flux.

Tannic acid inhibition of amino acid and sugar absorption by mouse and vole intestine: Tests following acute and subchronic exposure

The acute effects of tannin (tannic acid; TA) on nutrient absorption were studied by measuring sugar and amino acid uptake across the brash border (luminal membrane) of intact intestine in the presence and absence of TA. Incubation of tissue for 4-9 min in TA solution (1 mg/ml) caused a reduction in passive influx ofL-glucose in voles and mice and a reduction in carrier-mediated influx ofD-glucose and total influx ofL-proline in mice, but not voles. In subchronic experiments, mice and voles were fed for 7-14 days a diet with 4% TA, but there was no significant effect on intestinal brush border uptake ofL-glucose,D-glucose, orL-proline (or three other amino acids tested in voles). In a synthesis of our study with others in the literature, three inferences are made from the patterns of effects across solutes, time scales of exposure, and species. First, the transport inhibitory effects following acute exposure are probably mediated by two processes: increased resistance to passive flux across an effective unstirred layer juxtaposed to the brush border membrane, perhaps due to tannin-mucin binding, and reduced Na(+)-coupled nutrient uptake across the intestinal brush border. Second, there is a species sensitivity difference in TA's effect on the second process. Third, the negative effects observed at the acute time scale in vitro do not necessarily occur in animals eating TA subchronically because little TA reaches the luminal membrane, or if it does its effects are quickly reversed when the tissue is removed and washed with solution free of TA.

Local (gut) and systemic metabolism of rats is altered by consumption of raw bean (Phaseolus vulgaris L var athropurpurea)

The composition of the raw legume Phaseolus vulgaris L. var. athropurpurea (PhVa) and its effects on the metabolism of young growing rats have been evaluated. The levels of protein, unsaturated fatty acids, carbohydrate, fibre and bioactive factors present in PhVa were comparable with those in other Phaseolus vulgaris varieties. However, the lectins of PhVa were predominantly of the leucoagglutinating type, and concentrated in the albumin protein fraction. Rats fed a diet (110 g total protein, 16.0 MJ/kg) in which PhVa meal provided about half of the protein excreted high levels of N in faeces and urine, and grew more slowly, than rats fed a high-quality control diet (ad libitum or pair-fed). Small intestine, large intestine and pancreas weights were increased (by almost 100 %, P<0.05), whilst skeletal muscle, thymus and spleen weights were reduced. Blood insulin (16.20 v. 0.50 mU/l, P<0.05, thyroxine, glucose, protein (60.5 v. 48.3 g/l, P<0.05) and LDL-cholesterol were lowered, whilst glucagon (155.3 v. 185.4 ng/l, P<0.05), triiodothyronine and urea were elevated, as were urinary urea, creatinine and glucose. These changes in the local (gut) and systemic metabolism of rats were probably mediated primarily by lectins in PhVa, which were concentrated in the albumin protein fraction, whereas in many other Phaseolus vulgaris lines they are distributed across the globulin and albumin fractions.

Utilization of different soy products as affected by age in chicks

Two experiments were conducted to evaluate the utilization of several different soy products at different ages in New Hampshire x Columbian male chicks. Six pens of eight chicks were fed dextrose-protein source diets (23% CP) containing 1 of 10 different protein sources from 0 to 21 d of age. Excreta were collected at 0 to 2, 3 to 4, 7, 14, and 21 d of age, and AMEn and amino acid (AA) digestibility were determined using acid-insoluble ash as a marker. Protein sources evaluated were as follows: Experiment 1--casein, soybean meal (SBM), soy protein concentrate (SPC), and soy protein isolate (SPI); Experiment 2-raw soyflakes, SBM, Williams 82 soybeans, heated Williams 82 soybeans, Kunitz-free soybeans (reduced trypsin inhibitor), lectin-free soybeans, and Kunitz/lectin-free soybeans. In Experiment 1, when comparing the MEn and AA digestibility values among diets at the same age, the ranking (from highest to lowest) for the four diets was casein, SPI, SPC, SBM. The MEn values increased (P < 0.05) with age for all four diets, with the increase being much smaller for the casein diet (3%) than the soy diets (mean increase of 13%). In Experiment 2, the SBM diet yielded the highest (P < 0.05) growth performance, MEn and AA digestibility values. The MEn and AA digestibility values of the Williams 82 soybeans, Kunitz-free soybeans, and lectin-free soybeans diets were much lower than those for the SBM diet. In general, the Kunitz/lectin-free soybeans yielded higher growth performance and MEn values than the Williams 82 soybeans, Kunitz-free soybeans, and lectin-free soybeans. The MEn values increased with age for most diets, and AA digestibility increased with age for the soyflake and Kunitz/ lectin-free soybean diets. Our results suggest there may be some potential benefits of feeding SPC or SPI during the first 1 to 3 wk posthatching and that underprocessed (under heated) soybeans should not be included in the diets of very young chicks.

Dry bean protein functionality

Dry beans are an important source of proteins, carbohydrates, dietary fiber, and certain minerals and vitamins in the human food supply. Among dry beans, Phaseolus beans are cultivated and consumed in the greatest quantity on a worldwide basis. Typically, most dry beans contain 15 to 25% protein on a dry weight basis (dwb). Water-soluble albumins and salt-soluble globulins, respectively, account for up to 10 to 30% and 45 to 70% of the total proteins (dwb). Dry bean albumins are typically composed of several different proteins, including lectins and enzyme inhibitors. A single 7S globulin dominates dry bean salt soluble fraction (globulins) and may account for up to 50 to 55% of the total proteins in the dry beans (dwb). Most dry bean proteins are deficient in sulfur amino acids, methionine, and cysteine, and therefore are of lower nutritional quality when compared with the animal proteins. Despite this limitation, dry beans make a significant contribution to the human dietary protein intake. In bean-based foods, dry bean proteins also serve additional functions that may include surface activity, hydration, and hydration-related properties, structure, and certain organoleptic properties. This article is intended to provide an overview of dry bean protein functionality with emphases on nutritional quality and hydration-related properties.

Fatores antinutricionais: inibidores de proteases e lectinas

Os fatores antinutricionais presentes em alimentos podem provocar efeitos fisiológicos adversos ou diminuir a biodisponibilidade de nutrientes. A maior questão sobre os riscos à saúde provocados por antinutrientes é o desconhecimento dos níveis de tolerância, do grau de variação do risco individual e da influência de fatores ambientais sobre a capacidade de detoxificação do organismo humano. Dentre os fatores antinutricionais os inibidores de proteases e as lectinas são considerados instáveis ao tratamento térmico. A hipertrofia pancreática causada pelos inibidores de tripsina tem sido relatada em alguns estudos com animais. As alterações da função fisiológica em animais causadas por ação de lectinas no intestino parecem estar relacionadas à especificidade destas substâncias com as células da mucosa intestinal. Os possíveis efeitos adversos dos inibidores de proteases e das lectinas na maioria das vezes são inferidos somente de experimentos com animais de laboratório.

Nutritional evaluation of lectin-free soybeans for poultry

This study evaluated the nutritional value of raw lectin-free soybeans in comparison with raw Kunitz trypsin inhibitor-free soybeans, raw conventional soybeans, and commercial heat processed soybean meal (SBM). Analyzed lectin values (milligrams per kilogram) were 7.2, 7.1, and < 0.00015 for the Kunitz-free, conventional, and lectin-free soybeans, respectively. Three experiments were conducted using New Hampshire x Columbian male chicks fed 23% CP dextrose-soybean diets from 8 to 17 d of age. Growth performance of chicks fed lectin-free soybeans was greater (P < 0.05) than that of chicks fed raw conventional soybeans in all three experiments. However, performance of chicks fed lectin-free soybeans was lower than that of chicks fed Kunitz-free soybeans or SBM. The SBM yielded weight gains and feed efficiencies that were much higher than those observed from any of the raw soybeans. True amino acid digestibility and TMEn of the lectin-free and conventional soybeans were determined using the precision-fed cecectomized rooster assay. Seven roosters were crop-intubated with 30 g of soybeans and excreta were collected for 48 h. Digestibility coefficients of most amino acids for lectin-free soybeans were 5 to 8 percentage units higher than those for conventional soybeans, but the differences were not significant (P > 0.05). Likewise, the TMEn for lectin-free soybeans was 11% higher than that for raw conventional soybeans (3.577 vs 3.227 kcal/g DM) but the difference was not significant (P > 0.05). The results of this study indicate that the nutritional value of raw lectin-free soybeans is greater than raw conventional soybeans but is less than raw Kunitz-free soybeans and SBM, suggesting that trypsin inhibitor is a greater antinutritional factor than lectins.

Lipid accumulation in obese Zucker rats is reduced by inclusion of raw kidney bean (Phaseolus vulgaris) in the diet

The effects of inclusion of different levels of raw kidney bean (Phaseolus vulgaris) of high lectin content (27 g/kg meal) in a high-quality (lactalbumin) control diet were tested in nutritional trials on the growth and metabolism of obese Zucker (fafa) rats and their lean littermates in comparison with pair-fed controls. All diets contained 100 g total protein/kg and either 50 g lipids/kg (low fat) or 150 g lipids/kg (moderate fat). The growth of both obese and lean rats on bean diets was retarded by the daily bean intake in a dose-dependent manner. However, most of this was because bean-fed rats contained less body fat than the controls after 10 d. Thus, after feeding low-fat diets containing up to 130 g kidney bean/kg (lectin intake < or = 0.2 g/kg body weight (BW) per d) in both 10 d and 70 d trials, the bodies of obese rats contained less fat but not protein than their pair-fed controls. Moreover, by increasing the lipid content of the diet to 150 g/kg, the level of bean inclusion could be increased to 280 g/kg (lectin intake > or = 0.4 g/kg BW per d) without loss of body protein and skeletal muscle. Although these rats contained more body fat than those which were fed on low-fat diets, their weight reduction could be accounted for exclusively by reduced lipid content. In contrast, significant body protein loss occurred when the same diet of high lectin content was fed to lean littermates. Plasma insulin levels were significantly depressed in the obese Zucker rats on bean diets but the pancreas was not significantly enlarged nor its insulin content changed in 10 d trials. However, significant pancreatic growth occurred on long-term (70 d) bean feeding compared with pair-fed controls. The results suggest that, in addition to animal nutrition, it may also be possible to use the bean lectin as a dietary adjunct or therapeutic agent to stimulate gut function and ameliorate obesity if a safe and effective dose-range can be established for human subjects.

Reversible effect of phytohaemagglutinin on the growth and metabolism of rat gastrointestinal tract

The lectin, phytohaemagglutinin, present in beans survives passage through the gastrointestinal tract in a biologically and immunologically intact form. It is known that by binding to the brush border membranes of the small intestine phytohaemagglutinin induces its hyperplastic growth. However, its effect on the other parts of the gut are not known. This study considered the dose and time dependent changes in the gastrointestinal tract exposed to phytohaemagglutinin. Lectin binding was detected by polyclonal antibodies using PAP staining to the surface and the parietal cell region of the stomach, the brush border epithelium of the small intestine and to the surface membrane of the caecum and colon. To characterise the metabolic changes in the gut organ weights, protein, RNA, DNA, and polyamine contents were measured. While phytohaemagglutinin induced a dose and time dependent growth of the small intestine by lengthening the tissue and thickening the gut wall by increasing the number of crypt cells, the lectin also changed the size and metabolism of the large intestine and pancreas, but this growth was by hypertrophy. Phytohaemagglutinin in the diet influences the size, metabolism, and function of the entire digestive tract. The lectin induced changes were fully or partially reversed within three days.

Clinical and microbiological field studies in The Netherlands of diarrhoea in pigs at weaning

A longitudinal study investigated the clinical signs and aspects of the aetiology of diarrhoea in pigs at weaning. Two litters of pigs were randomly selected from each of four Dutch herds with a history of diarrhoea after weaning. The pigs were inspected and faecal samples were collected daily. Before weaning, enterotoxigenic Escherichia coli was isolated from only two pigs but after weaning from all the pigs. Before and after weaning, rotaviruses were detected in almost all the pigs during one to four episodes. Rotavirus or enterotoxigenic E coli were generally detected when the pigs had diarrhoea; however, they were also encountered in normal faeces. In many faecal samples from pigs with diarrhoea no pathogenic agent was detected. In almost all the pigs after weaning, E coli types appeared and predominated transiently before they were superseded by another type. This study confirms the results of others in showing that rotaviruses and E coli are important in the aetiology of diarrhoea in pigs at weaning. However, diarrhoea after weaning is probably not caused by these two agents alone; other factors also probably contribute to the syndrome.

Hard-to-cook phenomenon in common beans--a review

Legumes are one of the world's most important sources of food supply, especially in developing countries, in terms of food energy as well as nutrients. Common beans are a good source of proteins, vitamins (thiamine, riboflavin, niacin, vitamin B6) and certain minerals (Ca, Fe, Cu, Zn, P, K, and Mg). They are an excellent source of complex carbohydrates and polyunsaturated free fatty acids (linoleic, linolenic). However, common beans have several undesirable attributes, such as long cooking times, being enzyme inhibitors, phytates, flatus factors, and phenolic compounds, having a "beany" flavor, and being lectins and allergens, which should be removed or eliminated for effective utilization. Grain quality of common beans is determined by factors such as acceptability by the consumer, soaking characteristics, cooking quality, and nutritive value. Acceptability characteristics include a wide variety of attributes, such as grain size, shape, color, appearance, stability under storage conditions, cooking properties, quality of the product obtained, and flavor. Storage of common beans under adverse conditions of high temperature and high humidity renders them susceptible to a hardening phenomenon, also known as the hard-to-cook (HTC) defect. Beans with this defect are characterized by extended cooking times for cotyledon softening, are less acceptable to the consumer, and are of lower nutritive value. Mechanisms involved in the HTC defect have not been elucidated satisfactorily. Attempts to provide a definitive explanation of this phenomenon have not been successful. The most important hypotheses that have been proposed to explain the cause of bean hardening are (1) lipid oxidation and/or polymerization, (2) formation of insoluble pectates, (3) lignification of middle lamella, and (4) multiple mechanisms. Most researchers have reported that the defect develops in the cotyledons. Recently, some authors have suggested that the seed coat plays a significant role in the process of common bean hardening. A better knowledge of cotyledon and seed coat microstructure may lead to a better understanding of the causes of seed hardness. In order to prevent the development of the HTC defect several procedures have been proposed: (1) appropriate storage, (2) controlled atmospheres, and (3) pretreatments. Probably, the most workable solution to the hardening phenomenon may be the development of materials less prone to HTC phenomenon. Decreasing cooking time, increasing nutritive value, and improving sensory properties of seeds with HTC defect would have great nutritional and economical impact.(ABSTRACT TRUNCATED AT 400 WORDS)

Soybean protein isolate and soybean lectin inhibit iron absorption in rats

Inhibitory effects of soybean protein isolate (SPI) and soybean lectin on the intestinal absorption of nonheme iron were investigated by in vivo studies in rats. Rats fed the SPI-based diet absorbed significantly less iron than did control rats fed the casein-based diet. Supplementing the SPI diets with 8% D-galactose significantly increased the incorporation of iron into liver ferritin, although D-galactose did not significantly increase iron absorption. Heat treatment of SPI significantly increased iron absorption. Ascorbate did not enhance iron absorption in rats fed the SPI-based diet. The presence of lectin in an aqueous extract of SPI was suggested by hemagglutination activity as well as by immunoreactivity with soybean lectin antibody. Soybean lectin introduced into ligated segments of the upper small intestine of rats inhibited ferrous iron absorption. This inhibitory effect, especially in the mucosal uptake, was significantly improved by addition of N-acetyl-D-galactosamine to soybean lectin. Soybean lectin had no effect on ferric iron absorption. Our results suggest that a portion of the reduction in iron absorption in rats fed SPI may be due to lectins.

Analysis of differentiation and transformation of cells by lectins

During differentiation cells are known to change their biological behavior according to their genotype. This is thought to be accompanied by a modulation of cell surface determinants expressed on the outer cell membrane. Vice versa, cell surface molecules are suggested to mediate extracellular signals to the genome. Most of these molecules integrated in the cell membrane have been proven to be glycoconjugates. The carbohydrate moieties of these molecules can be detected by means of lectins that are characterized by their ability to react specifically with distinct terminal sugar sequences. Thus, lectins have been used as appropriate tools for studying the modulation of functionally important membrane-associated molecules during the differentiation of cells, in particular of B- and T-lymphocytes. Moreover, lectins have been proven to distinguish between differentiated cells and malignant cell clones, according to the hypothesis that transformed cells possess a glycoconjugate profile that corresponds to the stage of differentiation at which they are arrested. Since lectins, like monoclonal antibodies, make it possible to study functionally important molecules that are associated with differentiation and malignancy, they might be of value for diagnostic purposes and, moreover, for analyzing malignant transformation.

Tomato lectin resists digestion in the mammalian alimentary canal and binds to intestinal villi without deleterious effects

Experiments were designed to investigate whether orally consumed tomato lectin could resist the digestive process and function as a lectin within the alimentary canal. Rats fed on a tomato lectin-rich diet passed faeces containing serologically detectable tomato lectin, and the lectin could be shown by immunoperoxidase staining bound to intestinal villi. Moreover, radioactivity was mainly recovered from the alimentary canal 3h after 125I-labelled tomato lectin administration with only traces in the circulation or internal organs. Radioactivity absorbed into the human circulation after consumption of 125I-labelled tomato lectin was also less than that expected for a digestable protein.

Bean lectins : 5. Quantitative genetic variation in seed lectins of Phaseolus vulgaris L. and its relationship to qualitative lectin variation

Seeds of forty bean cultivars having different lectin types based on two-dimensional isoelectric focusing-sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF-SDS/PAGE) were analyzed for quantities of lectin, phaseolin and total protein. Significant differences were found among groups of cultivars with different lectin types for the quantity of lectin and phaseolin. Cultivars with more complex lectin types based on IEF-SDS/PAGE tended to have higher quantities of lectin and lower quantities of phaseolin than cultivars with simple lectin types. An association between lectin type and the quantity of lectin and phaseolin was found also in the seeds of F2 plants that segregated in a Mendelian fashion for two lectin types. Seeds from plants with the complex lectin type had more lectin and less phaseolin than seeds from plants with the simple lectin type. Therefore, the genes controlling qualitative lectin variation also may influence the quantitative variation of lectin and phaseolin. The results of this study are related to other studies on the quantitative variation for seed proteins and to the possible molecular basis for variation in the quantity of lectins in beans.

Dry beans of Phaseolus. A review. Part 2. Chemical composition: carbohydrates, fiber, minerals, vitamins, and lipids

Beans of Phaseolus are an important food crop both economically and nutritionally, and are cultivated and consumed worldwide. With ever rising costs of meats and fresh fruits and vegetables, dry beans are expected to contribute more to the human nutrition in coming years. Traditionally, they have been referred to as "poor man's meat" and have contributed significantly to the diets of many people of several countries in Asia, Africa, Middle East, and South America. In recent years, a renewed interest in bean research in Western European countries and the U.S. is evident. In this review, certain biochemical, technological, nutritional, and toxicological aspects are discussed and the limitations and problems associated with dry beans of Phaseolus as human food are addressed.

Dry beans of Phaseolus: a review. Part 3

Beans of Phaseolus are important food crops both economically and nutritionally, and are cultivated and consumed world wide. With ever rising costs of meats, fresh fruits, and vegetables, dry beans are expected to contribute more to the human nutrition in coming years. Traditionally, they have been referred to as "poor man's meat" and have contributed significantly to the diets of many people of several countries in Asia, Africa, the Middle East, and South America. In recent years, a renewed interest in bean research in Western European countries and the U.S. is evident. In this review, certain biochemical, technological, nutritional, and toxicological aspects are discussed and the limitations and problems associated with dry beans of Phaseolus as human food are addressed.

Comparative study on the amino acids composition in three local Phaseolus vulgaris seeds varieties

The overall amino acid composition of the three varieties of Phaseolus vulgaris seeds were similar. All had a relative deficiency in the sulphur-containing amino acids, moreover, there was a negative correlation between sulphur amino acid content and the percentage of seed proteins. The lysine content of the Phaseolus seeds was relatively high, the amount ranged from 8.05 to 8.63 g/16 g N. Tryptophan was slightly higher for Giza variety than the others. The highest levels of free amino acids were recorded for Contender variety and Swissblan one. Cystine, phenylalanine and tyrosine were absent from the extracts of the three varieties.

A survey of the nutritional and haemagglutination properties of legume seeds generally available in the UK

Eighty-five samples from fifteen different legume seed lines generally available in the UK were examined by measurements of their net protein utilization by rats and by haemagglutination tests with erythrocytes from a number of different animal species. From these results the seeds were classified into four broad groups. Group a seeds from most varieties of kidney (Phaseolus vulgaris), runner (Phaseolus coccineus) and tepary (Phaseolus acutifolius) beans showed high reactivity with all cell types and were also highly toxic. Group b, which contained seeds from lima or butter beans (Phaseolus lunatus) and winged bean (Psophocarpus tetragonolobus), agglutinated only human and pronase-treated rat erythrocytes. These seeds did not support proper growth of the rats although the animals survived the 10 d experimental period. Group c consisted of seeds from lentils (Lens culinaris), peas (Pisum sativum), chick-peas (Cicer arietinum), blackeyed peas (Vigna sinensis), pigeon peas (Cajanus cajan), mung beans (Phaseolus aureus), field or broad beans (Vicia faba) and aduki beans (Phaseolus angularis). These generally had low reactivity with all cells and were non-toxic. Group d, represented by soya (Glycine max) and pinto (Phaseolus vulgaris) beans, generally had low reactivity with all cells but caused growth depression at certain dietary concentrations. This growth depression was probably mainly due to antinutritional factors other than lectins. Lectins from group a seeds showed many structural and immunological similarities. However the subunit composition of the lectin from the tepary bean samples was different from that of the other bean lectins in this or any other groups.

Bean lectins : Part 1: Relationships between agglutinating activity and electrophoretic variation in the lectin-containing G2/albumin seed proteins of french bean (Phaseolus vulgaris L.)

Single seeds of over 100 bean cultivars were analyzed by two-dimensional electrophoresis. The cultivars could be classified into eight groups by virtue of their G2/albumin electrophoretic patterns: TG2, SG2, VG2, PrG2, BG2, MG2, PG2, and PiG2, The polypeptide compositions of these types were largely inter-related having particular polypeptides in common. It was possible to correlate the G2/albumin patterns with agglutinating activity of cow and rabbit blood cells as measured by the agglutination ratio (minimum concentration of extract required to agglutinate cow blood cells: minimum concentration of extract required to agglutinate rabbit blood cells). The active lectin polypeptides were identified by extracting lectins from agglutinated erythrocytes and by comparing the qualitative similarities and differences of the G2/albumin patterns and their agglutination activities. A reference catalogue of over 100 bean cultivars giving their phaseolin and G2/albumin electrophoretic patterns, and agglutination ratios is presented.

Recent advances in the study of the nutritional toxicity of kidney bean (Phaseolus vulgaris) lectins in rats

The main toxic component isolated from several varieties of kidney bean (Phaseolus vulgaris) is a haemagglutinating lectin. The inclusion in rat diets of raw kidney beans or purified bean lectins results in abnormal development of microvilli in the small intestine. Immunocytochemical investigations have provided evidence that this lesion is associated with the binding of lectins to the luminal surfaces of enterocytes. The lectin-induced disruption of intestinal microvilli may result in interference with the intermediate and final stages of nutrient hydrolysis in the gut. In nitrogen balance studies it was found that rats ingesting pure bean lectins were in negative nitrogen balance. These nitrogen losses may have been partly the result of systemic effects, possibly caused by a selective uptake of lectins by the gut.