Bioprocessing of common pulses changed seed microstructures, and improved dipeptidyl peptidase-IV and α-glucosidase inhibitory activities

Abstract

Type 2 diabetes mellitus (T2DM) is a leading cause of death globally. T2DM patients experience glucose intolerance, and inhibitors of dipeptidyl peptidase IV (DPP-IV) and α-glucosidase are used as drugs for T2DM management. DPP-IV and α-glucosidase inhibitors are also naturally contained in foods, but their potency can be affected by the food matrix and processing methods. In this study, germination and solid-state fermentation (SSF) were used to alter pulse seed microstructures, to convert compounds into more bioactive forms, and to improve their bioaccessibility. Germination substantially modified the seed microstructure, protein digestibility, contents and profiles of phenolic compounds in all the pulses. It also increased DPP-IV and α-glucosidase inhibitory activities in chickpeas, faba beans and yellow peas. Compared to germination, SSF with Lactobacillus plantarum changed the content and the profile of phenolic compounds mainly in yellow peas and green lentils because of greater disruption of the seed cell wall. In the same pulses, heat treatment and SSF of flour increased DPP-IV and α-glucosidase inhibitory activities. The results of this study suggest that germination and SSF with L. plantarum are effective and simple methods for modulating phenolic and protein profiles of common pulses and improve the action on DPP-IV and α-glucosidase.

Figure 1

Enzyme inhibitory activity of bioprocessed pulses after in vitro digestion. (Panels A,B): DPP-IV inhibition of germinated (A) and solid state fermented (B) pulse samples. Values are expressed as milliequivalent Diprotin A (mM Diprotin A Eqv/100 mg DW). (Panel C,D): α-glucosidase inhibition of germinated (C) and solid state fermented (D) pulse samples. Values are expressed as milliequivalent Acarbose (mM Acarbose Evq/100 mg DW). CP: chickpea, FB: faba bean, KB: kidney bean, GL: green lentil, YP: yellow pea; S: soaked, SSF: solid state fermentation, HT: heat treatment, G: grinding. Data are expressed as mean ± SD of three independent replicates.

Figure 2

SDS-PAGE profiles of water-soluble extracts obtained from yellow peas (Panels A,B) and green lentils (Panels C,D) by solid state fermentation with Lactobacillus plantarum at 37 °C for 48 h (Panels A,C) and germination (Panel B,D). (Panels A,C): S1–S3: soaking (S1) followed by SSF (S2) and simulated gastrointestinal digestion (S3); A1–A3: autoclaving (A1) followed by SSF (A2) and simulated gastrointestinal digestion (A3); G1-–G3: grinding (G1) followed by SSF (G2) and simulated gastrointestinal digestion (G3). Panel B,D: D0-D3: day 0 (D0), 3 (D3) and 5 (D5) of germination at room temperature (23 °C) in the darkness. ab: albumin fraction; lβ: legumin β; lc: lectin; lα: legumin α; pv: provicilin; vc: vicilin; cv: convicilin; lx: lipoxygenase; 11s-g: 11s globulin.

Figure 3

Panel A–F: Yellow pea visualised by Toluidine blue O. Top: seed coat (testa), brightfield, 20×. Bottom: cotyledon, brightfield, 40×. Panels A,D: soaked; B,E: germinated; Panels C,F: solid state fermented with L. plantarum. c: cuticle; p: palisade cells; o- osteosclereids; pr: parenchyma; al: aleurone; es: endosperm; CW: cell wall; CM: cell membrane; ML: middle lamella; ST: starch; PT: protein. Panels G–M: green lentils visualised by Toluidine blue O. Top: seed coat (testa), brightfield, 10×. Bottom: cotyledon, brightfield, 20×. Panels G,K: soaked; Panels H,L: germinated; Panels J,M: solid state fermented with L. plantarum.

Figure 4

Yellow pea (Panels A–C) and green lentil (Panels D–F) visualised by Calcoflour White Stain, UV light, 20×. (Panels A,D): soaked; (Panels B,E): germinated; (Panels C,F): solid state fermented with L. plantarum.