Optimization and sustained release of green lentil polyphenols through instant controlled pressure drop and encapsulation in PLGA nanoparticles

Abstract

Throughout history, legumes have been part of human consumption for their nutritional content and because is an easy crop to cultivate, it can grow in both cold and warm climates. One type of legumes are lentils, consumed worldwide. In Mexico, lentils are consumed by 70% of Mexican adults. Among the lentil varieties, green lentils stand out for having the highest polyphenol content, which makes them an excellent candidate for human consumption. However, the traditional way of cooking lentils requires prolonged times in boiling water. This causes a significant loss of the number of polyphenols present in lentils. Polyphenols have the ability to reduce the prevalence of suffering from chronic degenerative diseases, because they have antioxidants and anti-inflammatories properties. However, the chemical stability of polyphenols is compromised by different factors like the chemical structure, temperature, pH, isomerizations, enzymes, degradation, and oxidation, among others. This study subjected the green lentils to instant controlled pressure drop (DIC) and measured the polyphenol amount, flavonoids and antioxidant capacity 1,1 -diphenyl-2-picrylhydrazyl (DPPH) and Trolox equivalent antioxidant capacity (TEAC and DPPH), with 13 different treatments by varying pressure and time. The results showed that the polyphenols were the only parameter affected by DIC and the best conditions were less than 160 s and less than 0.1 MPa, and the best treatment was the DIC treatment 11, with 0.1 MPa for 135 s. Surprisingly, apparently new polyphenols appeared in the treated lentils due to the physical stress secondary to DIC, and in consequence the biosynthesis of polyphenols. After DIC, the best green lentil treatment was selected (DIC 11). The polyphenolic extract was obtained and nano encapsulated in poly lactic-co-glycolic acid (PLGA) using five different extract volumes (100, 250, 500, 750 and 1000 𝜇L). The nanoparticles were spherical in shape, with negative zeta potential charge (~ 20 mV), and all the syntheses produced particles, with average sizes ranging between 300 to 1100 nm. The polyphenol released was evaluated in PBS at pH 5.5 and 7.4. The release followed a triphasic controlled release, a lag phase of 24 h, a burst and diffusion phase from 24 h to 372 h, up to 15 days, and finally the saturation phase. The combination of the DIC technology as a pretreatment for green lentils and the nanoencapsulation in PLGA nanoparticles, improved the extraction and preserved the polyphenols profile of green lentils, on the other hand, nanoencapsulation protected the polyphenols and reached a controlled polyphenol release for up to 15 days.