## 3 Encapsulation Techniques for Improving Phenolic Compounds Functionality
### Encapsulated Phenolic Compounds as Antidiabetic Agents
Resveratrol is a polyphenol found in grapes and nuts that has several pharmacological effects, including anti-inflammatory, antioxidant, platelet-enhancing, analgesic, neuroprotective, cardioprotective, and anti-aging [108]. Some studies have found that resveratrol has promising properties for treating T2D [115]. Resveratrol-loaded nanoliposomes were prepared to alleviate diabetes in diabetic rat models. Compared to free resveratrol, the nanoformulation increased the expression of ROS-inactivating enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), in diabetic pancreatic \(\beta\) TC cells and significantly decreased elevated glucose levels simultaneously with increasing insulin levels [106]. In another study, resveratrol nanocapsules, prepared by interfacial deposition, were tested for their effect on insulin resistance in mice with induced metabolic syndrome, using the quantitative insulin sensitivity check index (QUICKI) as a diagnostic tool [116]. The treatment with resveratrol nanocapsules successfully regulated insulin and glucose levels and controlled the QUICKI index within the healthy range. Additionally, systolic and diastolic blood pressure were also regulated in mice treated with resveratrol nanocapsules [116]. Tannic acid is a specific form of tannin, a polyphenol compound, found in all above-ground plant tissues. It has been well studied for its antioxidant, antimutagenic, and anticarcinogenic properties [117; 118]. An _in vitro_ study using a gastrointestinal tract model, investigated the inhibitory effect of tannic acid on \(\alpha\)-amylase as a tool to control and prevent diabetes mellitus and obesity [119]. The study demonstrated that tannic acid inhibits \(\alpha\)-amylase very effectively, showing better results than a commercial starch blocker (Phase 2 Starch Blocker). However, the authors noted that inhibition of \(\alpha\)-amylase in the gastrointestinal tract is complex when administered orally due to the non-specific and reversible non-competitive interactions with other proteins [119]. To protect tannic acid from non-specific interactions during oral administration, the authors encapsulated the bioactive in calcium alginate microspheres. The results showed that this delivery system could protect the tannic acid from proteins in the stomach, provide a controlled release, and efficiently inhibit \(\alpha\)-amylase activity in the small intestine [119]. In another study, a polyphenol-rich herbal formulation was microencapsulated by a freeze-drying process using different combinations of gum arabic, gelatin, and maltodextrin as wall materials [82]. The antioxidant activity, bioavailability, and anti-diabetic potential (_In vitro_ inhibition of \(\alpha\)-amylase and \(\alpha\)-glucosidase) of the obtained microcapsules were tested and compared with the free extract. Amongst all tested products, microencapsulated containing a combination of 5% gum arabic and 5% maltodextrin and formulations with a wall composed of 10% gum Arabic enabled the best bioavailability ratios (50% and 40%, respectively). These two formulations also had the best results in terms of preserving antioxidant activity and the highest _in vitro_ anti-diabetic potential due to a high potency for inhibiting \(\alpha\)-amylase and \(\alpha\)-glucosidase activities. In addition, these formulations were tested for acute toxicity in mice with no signs of toxicity at a dose of 2000 mg/kg administered by gavage [82].