###### Abstract  
Phenolic compounds are food-derived bioactive compounds well-known for their antioxidant and anti-inflammatory properties. They are in the spotlight for the management of diabetes due to their positive effects on glucose homeostasis. **Materials and methods:** We have performed a literature review on the main topics related to the application of phenolic compounds as functional food ingredients. This includes extraction and purification from vegetable sources and agro-industrial by-products, encapsulation to improve their solubility and bioavailability, and preclinical and clinical evidence linking these compounds with anti-diabetic activity. **Objectives:** (1) provide an understanding of the role of phenolic compounds on diabetes; (2) identify green technologies for phenolic compounds extraction from agri-food by-products following a biorefinery scheme; (3) underline the relevance of encapsulation techniques using nanotechnology to improve their bioavailability; (4) discuss the therapeutic efficacy of polyphenols. **Results**: This review compiles recent relevant research on phenolic compounds extraction from renewable resources, their purification from agri-food by-products, and encapsulation strategies using eco-friendly processes. It also highlights the preclinical and clinical evidence on phenolic compounds' antidiabetic activity, giving insight into their mechanisms of action. **Conclusions**: This review explores the latest advances in polyphenols and how their benefits in glucose homeostasis can be applied toward improving the health of patients with diabetes and related conditions. bioactives; encapsulation; gut-brain axis; obesity; inflammation; clinical trials; sustainable extraction +
Footnote †: journal: _Scienced Reviews_  
against diabetes has created new insights for developing polyphenol-rich functional foods and nutritional supplements [4,7]. Phenolic compounds are the most prominent family of antioxidant compounds in foods and constitute an essential part of the human diet [8]. These bioactive compounds represent a diverse group of secondary metabolites, commonly appearing in many foods such as fruits, vegetables, coffee, wine, tea, cocoa, or cereals [6]. With more than 8000 phenolic structure variants found in whole plant foods, phenolic compounds are subdivided into different groups based on the number of phenol rings and structural elements that bind these rings to one another, including phenolic acids, flavonoids, stillenes, lignans, and polymeric lignans [9,10]. The phenolic acids are subdivided into two classes: hydroxybenzoic (e.g., gallic acid) and hydroxycinnamic (e.g., caffeic, ferulic, and coumaric acid) [10]. Flavonoids are flavones, flavanones, anthocyanins, and flavanols. Stilbenes are present in low quantities in the human diet, the best-known compound being _trans_-resveratrol, primarily detected in grapes and red wine [10,11]. Tannins are a group of water-soluble phenolic compounds represented in two structural groups: gallotannins and ellagitannins of hydrolysate tannins [10]. A small group of phenolic compounds with two aromatic rings substituted with hydroxyls and linked by an aliphatic chain containing carbonyl groups is called diferuloylmethane, better known as curcumin in the dietary spice turmeric, which is widely used as a herbal remedy [10]. Phenolic compounds present several beneficial effects on blood glucose management in diabetes conditions (Figure 1). Indeed, these phenolic compounds have hypoglycemic effects such as lowering the intestinal absorption of dietary carbohydrates, modulation of enzymes involved in glucose metabolism, enhancement of \(\beta\)-cell function and insulin action, insulin secretion, and antioxidative and anti-inflammatory properties [11]. Phenolic compounds have potent antioxidant activity by endogenous and exogenous mechanisms that complement and add to the role of antioxidant vitamins and enzymes as a defence against oxidative stress induced by excessive production of reactive oxygen species (ROS) [9,10].