Formation of inclusion compounds of (+)catechin with β-cyclodextrin in different complexation media: Spectral, thermal and antioxidant properties

Inclusion Complexes of Litsea cubeba (Lour.) Pers Essential Oil into β-Cyclodextrin: Preparation, Physicochemical Characterization, Cytotoxicity and Antifungal Activity

The uses of natural compounds, such as essential oils (EOs), are limited due to their instability to light, oxygen and temperature, factors that affect their application. Therefore, improving stability becomes necessary. The objective of this study was to prepare inclusion complexes of Litsea cubeba essential oil (LCEO) with β-cyclodextrin (β-CD) using physical mixing (PM), kneading (KN) and co-precipitation (CP) methods and to evaluate the efficiency of the complexes and their physicochemical properties using ATR-FTIR, FT-Raman, DSC and TG. The study also assessed cytotoxicity against human colorectal and cervical cancer cells and antifungal activity against Aspergillus flavus and Fusarium verticillioides. The complexation efficiency results presented significant evidence of LCEO:β-CD inclusion complex formation, with KN (83%) and CP (73%) being the best methods used in this study. All tested LCEO:β-CD inclusion complexes exhibited toxicity to HT-29 cells. Although the cytotoxic effect was less pronounced in HeLa tumor cells, LCEO-KN was more active against Hela than non-tumor cells. LCEO-KN and LCEO-CP inclusion complexes were efficient against both toxigenic fungi, A. flavus and F. verticillioides. Therefore, the molecular inclusion of LCEO into β-CD was successful, as well as the preliminary biological results, evidencing that the β-CD inclusion process may be a viable alternative to facilitate and increase future applications of this EO as therapeutic medication, food additive and natural antifungal agent.

Inclusion of a Catechol-Derived Hydrazinyl-Thiazole (CHT) in β-Cyclodextrin Nanocavity and Its Effect on Antioxidant Activity: A Calorimetric, Spectroscopic and Molecular Docking Approach

The aim of the present research was to obtain a supramolecular complex between a strong antioxidant compound previously reported by our group, in order to extend its antioxidant activity. The formation of the inclusion complex of a catechol hydrazinyl-thiazole derivative (CHT) and β-cyclodextrin in aqueous solution has been investigated using isothermal titration calorimetry (ITC), spectroscopic and theoretical methods. The stoichiometry of this inclusion complex was established to be equimolar (1:1) and its equilibrium constant was determined. An estimation of the thermodynamic parameters of the inclusion complex showed that it is an enthalpy and entropy-driven process. Our observations also show that hydrophobic interactions are the key interactions that prevail in the complex. ¹H NMR spectroscopic method was employed to study the inclusion process in an aqueous solution. Job plots derived from the ¹H NMR spectral data demonstrated 1:1 stoichiometry of the inclusion complex in a liquid state. A 2D NMR spectrum suggests the orientation of the aromatic ring of CHT inside the β-CD cavity. The antiradical activity of the complex was evaluated and compared with free CHT, indicating a delayed activity compared with free CHT. To obtain additional qualitative and visual insight into the particularity of CHT and β-CD interaction, molecular docking calculations have been performed.

Novel β-Cyclodextrin and Catnip Essential Oil Inclusion Complex and Its Tick Repellent Properties

Cyclodextrin inclusion complexes have been successfully used to encapsulate essential oils, improving their physicochemical properties and pharmacological effects. Besides being well-known for its effects on cats and other felines, catnip (Nepeta cataria) essential oil demonstrates repellency against blood-feeding pests such as mosquitoes. This study evaluates the tick repellency of catnip oil alone and encapsulated in β-cyclodextrin, prepared using the co-precipitation method at a 1:1 molar ratio. The physicochemical properties of this inclusion complex were characterized using GC-FID for encapsulation efficiency and yield and SPME/GC-MS for volatile emission. Qualitative assessment of complex formation was done by UV-Vis, FT-IR, ¹H NMR, and SEM analyses. Catnip oil at 5% (v/v) demonstrated significant tick repellency over time, being comparable to DEET as used in commercial products. The prepared [catnip: β-CD] inclusion complex exerted significant tick repellency at lower concentration of the essential oil (equivalent of 1% v/v). The inclusion complex showed that the release of the active ingredient was consistent after 6 h, which could improve the effective repellent duration. These results demonstrated the effective tick repellent activity of catnip essential oil and the successful synthesis of the inclusion complex, suggesting that β-CDs are promising carriers to improve catnip oil properties and to expand its use in repellent formulations for tick management.

Synthesis and characterization of a (+)-catechin and L-(+)-ascorbic acid cocrystal as a new functional ingredient for tea drinks

Tea (Camellia Sinensis) is one of the most popular drink, consumed as infusion or bottled ready to drink beverages. Although tea leaves contain many antioxidants compounds, after processing they can drastically decrease, sometimes up to a full degradation, as in the case of catechin, a very healthy flavan-3-ol. In this context, the synthesis of a cocrystal between (+)-catechin and L-(+)-ascorbic acid, was proved to be a useful strategy to make a new ingredient able to ameliorate the antioxidant profile of both infusions and bottled teas. The obtained cocrystal showed a three-fold higher solubility than (+)catechin and its formation was elucidated unambiguously by FT-IR, thermal (DSC) and diffraction (PXRD) analyses. Antioxidant characteristics of the samples were evaluated by colorimetric assays. As expected, infusions showed much better antioxidant features than ready-to-use lemon and peach teas. The same trend was confirmed after the addition of the cocrystal at two concentration levels. In particular, supplementation at concentration of 2 mg mL-1 improved the bottled tea antioxidant values to the level showed by the not-added infusion tea.

Separation, Identification, and Antidiabetic Activity of Catechin Isolated from Arbutus unedo L. Plant Roots

Phytopharmaceuticals play an essential role in medicine, since the need to investigate highly effective and safe drugs for the treatment of diabetes mellitus disease remains a significant challenge for modern medicine. Arbutus unedo L. root has various therapeutic properties, and has been used widely in the traditional medicine as an antidiabetic agent. The current study aimed to isolate the pharmacologically active compound from A. unedo roots using accelerated solvent extraction technology, to determine its chemical structure using different instrumental analytical methods, and also to evaluate the α-glucosidase inhibitory activity. The roots of A. unedo were exhaustively extracted by high-pressure static extraction using the Zippertex^® technology (Dionex-ASE, Paris, France), and the extract was mixed with XAD-16 resin to reach quantifiable amounts of active compounds which were identified by high-pressure liquid chromatography (HPLC), ¹H NMR (300 MHz), and ¹³C NMR. The antidiabetic activity of the isolated compound was evaluated using the α-glucosidase inhibitory assay. The active compound was isolated, and its structure was identified as catechin using instrumental analysis.The results revealed that the isolated compound has potential α-glucosidase inhibitory activity with an IC₅₀ value of 87.55 ± 2.23 μg/mL greater than acarbose. This was used as a positive control, which has an IC₅₀ value of 199.53 ± 1.12 μg/mL. According to the results achieved, the roots of A. unedo were considered the best source of catechin and the Zippertex^® technology method of extraction is the best method for isolation of this therapeutic active compound. In addition, the α-glucosidase inhibitory activity results confirmed the traditional use of A. unedo roots as an antidiabetic agent. Future clinical trials and investigations of antidiabetic and other pharmacological effects such as anticancer are required.

Nano- and micro-particles for delivery of catechins: Physical and biological performance

Catechins, present in many fruits and vegetables, have many health benefits, but they are prone to degradation. Nano- and micro-particle systems have been used to stabilise catechins when exposed to adverse environments and to improve their bioavailability after ingestion. This review discusses the inherent properties of various catechins, the design of delivery formulations and the properties of catechin-loaded nano- and micro-particles. The protection afforded to catechins during exposure to harsh environmental conditions and gastrointestinal tract transit is reviewed. The bioavailability and efficacy of encapsulated catechins, as assessed by various in vitro and in vivo conditions, are discussed. Bioavailability based on uptake in the upper gut alone underestimates the bioavailability as polyphenols. The caveats with interpretation of bioavailability based on various tests are discussed, when taking into consideration the pathways of catechin metabolism including the role of the gut microflora. However, taken together, the weight of the evidence suggests that there are potentially improved health benefits with the use of appropriately designed nano- and micro-particles for delivery of catechins. Further systematic studies on the metabolism and physiological effects of encapsulated catechins in vivo and clinical trials are needed to validate the bioefficacy of the encapsulated catechins.