Phenolic Bioactives From Plant-Based Foods for Glycemic Control

Abstract

Plant-based foods containing phenolic bioactives have human health protective functions relevant for combating diet and lifestyle-influenced chronic diseases, including type 2 diabetes (T2D). The molecular structural features of dietary phenolic bioactives allow antioxidant functions relevant for countering chronic oxidative stress-induced metabolic breakdown commonly associated with T2D. In addition to antioxidant properties, phenolic bioactives of diverse plant foods have therapeutic functional activities such as improving insulin sensitivity, reducing hepatic glucose output, inhibiting activity of key carbohydrate digestive enzymes, and modulating absorption of glucose in the bloodstream, thereby subsequently improving post-prandial glycemic control. These therapeutic functional properties have direct implications and benefits in the dietary management of T2D. Therefore, plant-based foods that are rich in phenolic bioactives are excellent dietary sources of therapeutic targets to improve overall glycemic control by managing chronic hyperglycemia and chronic oxidative stress, which are major contributing factors to T2D pathogenesis. However, in studies with diverse array of plant-based foods, concentration and composition of phenolic bioactives and their glycemic control relevant bioactivity can vary widely between different plant species, plant parts, and among different varieties/genotypes due to the different environmental and growing conditions, post-harvest storage, and food processing steps. This has allowed advances in innovative strategies to screen and optimize whole and processed plant derived foods and their ingredients based on their phenolic bioactive linked antioxidant and anti-hyperglycemic properties for their effective integration into T2D focused dietary solutions. In this review, different pre-harvest and post-harvest strategies and factors that influence phenolic bioactive-linked antioxidant and anti-hyperglycemic properties in diverse plant derived foods and derivation of extracts with therapeutic potential are highlighted and discussed. Additionally, novel bioprocessing strategies to enhance bioavailability and bioactivity of phenolics in plant-derived foods targeting optimum glycemic control and associated T2D therapeutic benefits are also advanced.

Keywords: alpha-amylase; alpha-glucosidase; anti-hyperglycemia; antioxidant; bioprocessing strategies; carbohydrate metabolism; phenolics; plant foods.

Figure 1

Glycemic Control Benefit Relevant Functional Properties of Plant Phenolics. Phenolics are dietary inhibitors of key enzymes involved in carbohydrate metabolism like α-amylase and α-glucosidase. Additionally, phenolics potentially inhibit dipeptidyl peptidase IV (DPP-IV), which is a dietary and therapeutic target to maintain glucose homeostasis. Select plant foods rich in phenolics also provide protection against chronic hypertension through inhibition of angiotensin-I-converting (ACE) enzyme.

Figure 2

Pre-Harvest Stress Inducible Strategies to Stimulate Biosynthesis of Human Health Protective Phenolic Bioactives in Food Plants. Mild stress induction at critical reproductive stage drive carbon flux towards biosynthesis of stress protective metabolites like phenolics through upregulation of pentose phosphate pathway (PPP), shikimate pathway, and phenylpropanoid pathway. Metabolically driven screening also help to find plant foods with optimum phenolic bioactive profile and associated anti-diabetic functionalities. Glucose-6-phopshate dehydrogenase (G6PDH); proline dehydrogenase (PDH); succinate dehydrogenase (SDH); superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX).

Figure 3

Post-harvest Bioprocessing Strategies to Enhance Mobilization, Bioavailability, and Bioactive Functionalities of Phenolics in Plant Foods. Sprouting, bio-elicitation, beneficial lactic acid bacteria-based fermentation, and different food processing and cooking strategies can be optimized and targeted to improve phenolic bioactive-linked antioxidant, anti-hyperglycemic and digestive health relevant benefits in plant foods from different geographical and ecological origins.