Lectins are a diverse class of proteins distributed extensively in nature. Among these proteins; legume lectins display a variety of interesting features including antimicrobial; insecticidal and antitumor activities. Because lectins recognize and bind to specific glycoconjugates present on the surface of cells and intracellular structures; they can serve as potential target molecules for developing practical applications in the fields of food; agriculture; health and pharmaceutical research. This review presents the current knowledge of the main structural characteristics of legume lectins and the relationship of structure to the exhibited specificities; provides an overview of their particular antimicrobial; insecticidal and antitumor biological activities and describes possible applications based on the pattern of recognized glyco-targets.

Zabrotes subfasciatus (Boheman) is the main pest of common beans (Phaselous vulgaris). Some wild legume seeds may contain lectins with insecticidal activities against this insect. The larval developments of Z. subfasciatus on seeds of Olneya tesota (a desert wild legume) and on artificial seeds containing purified PF2 lectin were evaluated. PF2 susceptibility to proteolysis was assessed by incubation with midgut extract at different times. PF2 binding to midgut glycoconjugates was assessed by histochemistry. A reduced level of oviposition and a lack of emergence of adult beetles were observed in O. tesota seeds (compared to common beans), and in artificial seeds containing PF2 at 0.5 and 1%. PF2 was resistant to larval midgut proteolysis for 24 h, while PHA-E (lectin control) was fully digested after 4 h. Histochemistry analysis of midguts incubated with PF2 showed recognition for microvillae and possibly with peritrophic gel. On the other hand, PHA-E exhibited no interaction with larval midgut glycoproteins. Proteolysis resistance and glycan recognition could in part explain why PF2 is toxic to Z. subfasciatus while PHA is not.

Currently, silver nanoparticles have boomed in food and medicine due to their potential applications, such as antibacterial and anticancer activity. These nanoparticles have been synthesized by several techniques; however, green synthesis has taken on greater importance due to the non-generation of toxic residues. Green synthesis has been constructed from plant parts; however, the new trend comprises the use of agri-food waste extracts, known as sustainable green synthesis. The use of agri-food waste reduces environmental pollution and confers on its added value. The main waste generated is found in agricultural crops and industry from fruits and vegetables, cereal, bagasse from the food industry, and alcoholic beverages, oil cake of the oil industry, among others. The main biomolecules in agri-food waste extracts include phenolic compounds, alkaloids, terpenes, cellulose, hemicellulose, lignin, and proteins, whose function is to reduce the agents of the silver ion. Therefore, the objective of this review was to promote the use of agri-food waste for the sustainable green synthesis of silver nanoparticles and its application as antibacterial and anticancer agents.