**Abstract**

Flavonoids are polyhydroxylated natural chemicals that have been shown to improve human health. These are a type of bioactive molecules that can be found in abundance in plants. These polyphenolic chemicals are naturally generated from plant metabolites. Before entering the intestine, flavonoid glycosides are deglycosylated, while aglycones can readily pass-through cell membranes. They are absorbed and transferred to the liver, where they undergo substantial metabolism, resulting in glucuronides, sulfates, and methylation compounds. These conjugates are responsible for the health-promoting possessions of flavonoids. The flavonol subclass was the first to be researched, with quercetin as the most common dietary flavonol, and information on other flavonoid subclasses is still developing. Cellular signaling pathways mediate the antidiabetic benefits of dietary flavonoids in the pancreas, liver, and skeletal muscle. Flavonoids modulate distinct signaling pathways in pancreatic cells, hepatocytes, adipocytes, and skeletal myofibers via acting on various molecular targets. Flavonoids may help people with diabetes firstly by improving hyperglycemia through glucose metabolism regulation in hepatocytes and secondly by reducing insulin resistance, inflammation, and oxidative stress in muscle and fat and by increasing glucose uptake in skeletal muscle and white adipose tissue. A greater understanding of the flavonoid pathway's regulatory mechanisms would likely favor the progress of novel bioprocessing techniques for the production of value-added plants with optimal flavonoid content.

**Keywords:** deglycosylated, hyperglycemia, molecular targets, plant metabolites, polyhydroxylated natural chemicals

### **1. Introduction**

Flavonoids are secondary metabolites found in high concentrations in vascular florae and minor amounts in lichens. They get to build up in all structures and matters at various periods of expansion and in response to conservational factors. These compounds are of prodigious significance to social nourishment and wellbeing, and their many characteristics in plant progress and variation in the atmosphere. They do help in the organoleptic eminence of plant-derived goods, as well as being helpful to social wellbeing and cell aging anticipation. Increased consumption of vegetables and fruits has been known to protect against cancer and cardiovascular disease. These are a major class of natural antioxidants found in a plant-based diet and may have a role in this protective effect. Fruits (cherry, grapes, and apple), vegetables (onion, broccoli, and spinach), beverages (coffee and tea), soy products, and basils are all good sources of flavonoids [1]. They can be found inside the cells of all plant tissues as well as on the exteriors of many plant tissues. The phenylpropanoid unit, C6C3, is a common building component in the carbon skeleton of these phenols. This route creates a wide range of plant phenols during biosynthesis. The molecular structure of this class of composites is created on a diphenyl propane (C6-C3-C6) skeleton with 2 aromatic rings joined by a 3-carbon "bridge" to form a 6-member heterocyclic ring. Flavonoids are classified into 3 groups based on the aromatic ring's link to the heterocyclic ring: flavonoids (2-phenylbenzopyrans), isoflavonoids (3-phenylbenzopyrans), and neoflavonoids (4-phenylbenzopyrans) [2]. They can be separated into numerous sets based on the degree of oxidation and saturation in the heterocyclic C-ring, as shown in **Figure 1**. Hydroxylation occurs in positions 3, 5, 7, 3′, 4′, and/or 5′ in flavonoids. Methylated, acylated, prenylated, or sulfated hydroxyl groups are frequently found.

**Figure 1.** *Subclasses of flavonoids.*

*Recent Advances in Flavonoid Metabolism: An Updated Review DOI: http://dx.doi.org/10.5772/intechopen.106243*

Flavonoids are commonly found in plants as O- or C-glycosides. Sugar substituents are destined to a hydroxyl group of the aglycone, commonly at site 3 or 7, in O-glycosides, whereas saccharide groups are connected to a carbon of the aglycone typically at site C6 or C8 in C-glycosides. Rhamnose, glucose, galactose, and arabinose are the most common saccharides. Plant metabolism, defense, signaling, disease, and symbiosis all benefit from flavonoids [3, 4]. These chemicals are accountable for floral color and are implicated in stress retort mechanisms, such as UV-B radiation [5, 6], microbial infection [7], and herbivore attacks by animals and insects [8].
