An Overview of Plant Phenolic Compounds and Their Importance in Human Nutrition and Management of Type 2 Diabetes

Abstract

In this paper, the biosynthesis process of phenolic compounds in plants is summarized, which include the shikimate, pentose phosphate and phenylpropanoid pathways. Plant phenolic compounds can act as antioxidants, structural polymers (lignin), attractants (flavonoids and carotenoids), UV screens (flavonoids), signal compounds (salicylic acid, flavonoids) and defense response chemicals (tannins, phytoalexins). From a human physiological standpoint, phenolic compounds are vital in defense responses, such as anti-aging, anti-inflammatory, antioxidant and anti-proliferative activities. Therefore, it is beneficial to eat such plant foods that have a high antioxidant compound content, which will cut down the incidence of certain chronic diseases, for instance diabetes, cancers and cardiovascular diseases, through the management of oxidative stress. Furthermore, berries and other fruits with low-amylase and high-glucosidase inhibitory activities could be thought of as candidate food items in the control of the early stages of hyperglycemia associated with type 2 diabetes.

Keywords: biosynthesis; complication; function; phenolic compounds; type 2 diabetes.

Figure 1

Common phenolic compounds in plants comprise an aromatic ring, bear one or more hydroxyl substituents and range from simple phenolic molecules to highly polymerized compounds (modified from Velderrain-Rodríguez et al., 2014) [2].

Figure 2

Biosynthesis of phenol compounds in the pentose phosphate, shikimate and phenylpropanoid pathways in plants (modified from Vattem et al., 2005, and Lin et al., 2010) [3,4].

Figure 3

Reactive oxygen (ROS) and nitrogen (RNS) species are highly reactive oxidized molecules, including superoxide, peroxide, singlet oxygen, hydroxyl radical, NO and OONO, that are constantly produced under normal cellular conditions, such as during homeostasis and impaired functions, which could lead to cellular damage, like ageing, disease and cell death (modified from Shetty et al., 2004.) [20].

Figure 4

OH radical scavenging ability of gallic and protocatechuic acids.

Figure 5

Fe²⁺ chelating ability of gallic and protocatechuic acids.