Lectins, trypsin inhibitors, BOAA and tannins in legumes and cereals and the effects of processing

Lectin Activity in Commonly Consumed Plant-Based Foods: Calling for Method Harmonization and Risk Assessment

Lectins are ubiquitous proteins characterized through their ability to bind different types of carbohydrates. It is well known that active lectins from insufficiently prepared legumes can cause adverse human health effects. The objective of this study was to determine the activity of lectins in samples across plant families representing commercially available edible plants, and the feasibility of inactivating lectins through soaking and boiling. Lectins were extracted from the plant families Adoxaceae, Amaranthaceae, Cannabaceae, Fabaceae, Gramineae, Lamiaceae, Linaceae, Pedaliaceae, and Solanaceae. A hemagglutination assay based on non-treated or trypsin treated rabbit erythrocytes was used to measure the lectin activity. The results showed the highest lectin activity in species from the Fabaceae family and demonstrated that soaking and boiling have an effect on the levels of active lectins. This is the first large study that combines lectin activity obtained from two different assays with raw and processed edible plants. In addition, we examined the current risk assessment, and regulations necessary for an adequate official reporting of results. We encourage the scientific community to further explore this field and agree on harmonized methods for analysis and interpretation, and hope that our methodology can initiate this development.

Pea polyphenolics and hydrolysis processing alter microbial community structure and early pathogen colonization in mice

Health benefits associated with pea consumption have been attributed to the fiber and polyphenolic content concentrated within the pea seed coat. However, the amount of pea polyphenols can vary between cultivars, and it has yet to be studied whether pea polyphenols impact the intestinal microbiota. We hypothesized that pea polyphenols promote a healthy microbiome that supports intestinal integrity and pathogen colonization resistance. To investigate the effects of pea polyphenols, pea cultivars rich and poor in proanthocyanidins were supplemented in raw or acid hydrolyzed form to an isocaloric diet in mice. Acid hydrolysis increases the absorption of pea polyphenols by cleaving polymeric proanthocyanidins to their readily absorbable anthocyanidin monomers. After 3 weeks of diet, mice were challenged with Citrobacter rodentium and pathogen colonization and inflammation were assessed. Counter to our hypothesis, pea seed coat fraction supplementation, especially the non-hydrolyzed proanthocyanidin-rich fraction diet adversely increased C. rodentium pathogen load and inflammation. Ileal, cecal and colon microbial communities were notably distinct between pea seed cultivar and hydrolysis processing. The consumption of intact proanthocyanidins decreased microbial diversity indicating that proanthocyanidins have antimicrobial properties. Together our results indicate supplementation of raw pea seed coat rich in proanthocyanidins adversely affect intestinal integrity. However, acid hydrolysis processing restored community structure and colonization resistance, and the anthocyanidin-rich fractions reduced weight gain on a high fat diet. Establishing a clear understanding of the effects of pea fiber and polyphenolic form on health will help to develop research-based pea products and dietary recommendations.

Differential Apoptotic and Mitogenic Effects of Lectins in Zebrafish

Plant lectins represent a major group of anti-nutritional factors that can be toxic to human and animals. However, the mechanisms by which lectins regulate cell fates are not well-understood. In the present study, the cellular and molecular impacts of three common lectins, agglutinins from wheat germ [wheat germ agglutinin (WGA)], soybean [soybean agglutinin (SBA)], and peanut [peanut agglutinin (PNA)] were examined in zebrafish embryo and liver cells. WGA and SBA were found to induce cell apoptosis both in vitro and in vivo, while PNA stimulated cell proliferation. WGA and SBA reduced levels of B cell lymphoma-2 (Bcl-2), phosphorylation of Bcl-2-associated death promoter (Bad), cyclin-dependent kinase 4 (Cdk4), and phosphorylation of the retinoblastoma (Rb). WGA and SBA also inhibited the activities of cell survival pathways including protein kinase B (Akt), extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), and target of rapamycin (Tor). Furthermore, WGA and SBA shifted the cellular metabolism characterized by reduced expression of glucose-6-phosphate dehydrogenase (g6pd) and increased expression of glutamine synthetase (glul) and glutamate dehydrogenase (glud). However, PNA showed the opposite effects toward these molecular markers compared to those of WGA and SBA. Therefore, our results revealed some plant lectins (WGA and SBA) were toxic while the other (PNA) was mitogenic. Further characterization of the distinct functions of individual lectins should be valuable for both nutrition and other potential applications.

Rice (Oryza sativa L.) containing the bar gene is compositionally equivalent to the nontransgenic counterpart

This publication presents an approach to assessing compositional equivalence between grain derived from glufosinate-tolerant rice grain, genetic event LLRICE62, and its nontransgenic counterpart. Rice was grown in the same manner as is common for commercial production, using either conventional weed control practices or glufosinate-ammonium herbicide. A two-season multisite trial design provided a robust data set to evaluate environmental effects between the sites. Statistical comparisons to test for equivalence were made between glufosinate-tolerant rice and a conventional counterpart variety. The key nutrients, carbohydrates, protein, iron, calcium, thiamin, riboflavin, and niacin, for which rice can be the principal dietary source, were investigated. The data demonstrate that rice containing the genetic locus LLRICE62 has the same nutritional value as its nontransgenic counterpart, and most results for nutritional components fall within the range of values reported for rice commodities in commerce.

Household-level technologies to improve the availability and preparation of adequate and safe complementary foods

Plant-based complementary foods are the main source of nutrients for many young children in developing countries. They may, however, present problems in providing nutritionally adequate and safe diets for older infants and young children. The high starch content leads to low-nutrient diets that are bulky and dense, with high levels of antinutritive factors such as phytates, tannins, lectins, and enzyme inhibitors. Phytates impair mineral bioavailability, lectins interfere with intestinal structure, and enzyme inhibitors inhibit digestive enzymes. In addition, there is often microbial contamination, which leads to diarrhea, growth-faltering, and impaired development, and the presence of chemical contaminants may lead to neurological disease and goiter. The fact that some fruits containing carotenoids are only available seasonally contributes to the vulnerability of children receiving predominantly plant-based diets. Traditional household food technologies have been used for centuries to improve the quality and safety of complementary foods. These include dehulling, peeling, soaking, germination, fermentation, and drying. While modern communities tend to reject these technologies in favor of more convenient fast-food preparations, there is now a resurgence of interest in older technologies as a possible means of improving the quality and safety of complementary foods when the basic diet cannot be changed for economic reasons. This paper describes the biology, safety, practicability, and acceptability of these traditional processes at the household or community level, as well as the gaps in research, so that more effective policies and programs can be implemented to improve the quality and safety of complementary foods.

Jack bean (Canavalia ensiformis): nutrition related aspects and needed nutrition research

The nutritional characteristics and food potentials of jack bean (Canavalia ensiformis) have been reviewed. The bean is a good sources of protein, 23% to 34%, and carbohydrate 55%. It is also a good source of Ca, Zn, P, Mg, Cu and Ni. Jack bean protein is adequate in most essential amino acids with the exception of methionine and cystine which may be nutritionally limiting. Antinutritional and toxic factors including trypsin inhibitors, hemagglutinins, cyanogen glucosides, oligosaccharides and others are present in jack bean. Properly processed jack bean could be used to prepare some of the popular dishes made from cowpea, peanut, pigeon pea and soybean. Industrial products such as protein concentrates and isolates, starch, flakes, grits and flours can be produced from the bean. Further research is needed to identify varieties with high protein and nutritional quality. Development of new highly nutritious food products based on whole or processed jack bean should increase production and expand use.

Effects of various water or hydrothermal treatments on certain antinutritional compounds in the seeds of the tribal pulse, Dolichos lablab var. vulgaris L

Effects of soaking, cooking and autoclaving on changes in polyphenols, phytohaemagglutinating activity, phytic acid, hydrogen cyanide (HCN), oligosaccharides and in vitro protein digestibility were investigated in seeds of Dolichos lablab var. vulgaris. Both distilled water and NaHCO3 solution soaking and autoclaving significantly reduced the contents of total free phenolics (85-88%) compared to raw seeds. Autoclaving (45 min) reduced the content of tannins by upto 72%. Soaking seemed to have limited effect in eliminating phytohaemagglutinating activity, whereas autoclaving (45 min) seemed to eliminate the haemagglutinating activity completely. The reduction in content of phytic acid was found to be some what greater in distilled water soaking (28%) compared to NaHCO3 solution soaking (22%). Only a limited loss in content of phytic acid was observed under cooking as well as autoclaving. Loss of HCN was greater under autoclaving (87%) compared to the other processes studied. Of the three sugars analysed, soaking reduced the level of verbascose more than that of stachyose and raffinose. Autoclaving reduced the content of oligosaccharides more efficiently (67-86%) than ordinary cooking (53-76%). Autoclaving improved the in vitro protein digestibility (IVPD) significantly (13%). Of all the different water and hydrothermal treatments studied autoclaving seemed to be the most efficient method in improving IVPD and eliminating the antinutrients investigated except phytic acid.

Effects of heat treatment and germination on trypsin and chymotrypsin inhibitory activities in sorghum (Sorghum bicolor (L.) Moench) seeds

There was no appreciable change in proteinase inhibitory activity in sorghum upon dry heat treatment. However, moist heating reduced trypsin and chymotrypsin inhibitors to a greater degree. Germination (5 days) brought about complete reduction in proteinase inhibitory activity.

Early effects and the possible mechanism of the effect of Concanavalin A (con A) and Phaseolus vulgaris lectin (PHA-P) on intestinal absorption of calcium and sucrose

Food lectins are known to affect the absorption of nutrients in experimental animals and altered morphology of the intestinal mucosa due to prolonged feeding of lectins is suggested to be the cause. However, toxic symptoms appear in humans immediately after consumption of lectin rich foods and the mechanism of this immediate action is not known. This study reports the immediate effect of Concanavalin A (Con A) and Phaseolus vulgaris lectin (PHA-P) on the absorption of Ca2+ and sucrose in rat intestine and the possible role of lectin-membrane interactions in the process. Calcium absorption was lowered by Con A, and this was observed to be due to Con A interacting with the intestinal mucosal membrane. Similarly, sucrose absorption was also altered, probably due to Con A binding the intestinal mucosal membrane. On the other hand PHA-P did not have any effect on either sucrose or calcium absorption. Results indicate that the effect on intestinal nutrient absorption depends on the type of lectin used (and its concentration) as well as the type of nutrient, besides the duration of exposure of intestinal mucosa to the lectin.