Preparation of New Glycerol-Based Dendrimers and Studies on Their Behavior toward Essential Oil Encapsulation.

Two new families of glycerol-based dendrimers (glyceroladendrimers (GADs) and glyceroclickdendrimers (GCDs)) have been synthesized. Three generations have been isolated for each family with good yields and were fully analyzed. The encapsulation of essential oils (citronella and cinnamon) in GADs, GCDs, and also in previously described glycerodendrimers GD-PAMAMs and GD-PPIs has been studied by dynamic-headspace gas chromatography coupled to mass spectrometry. The retention rates obtained were from -35.8 to 26.65% for citronella essential oil and from 2.14 to 38.84% for the cinnamon essential oil. In addition, the best results were obtained with GD-PAMAMs and GD-PPIs of higher generation. The interaction study between essential oils or more precisely their major components have been performed through NMR spectroscopy (1H NMR and DOSY NMR). No direct interactions between dendrimers and essential oils have been observed, but a surprising behavior of compression of the dendrimer in stable emulsions was observed. Indeed, the hydrodynamic radius of GD-PPI-3 has been reduced in the presence of cinnamon essential oil.

Cinnamomum zeylanicum Essential Oil Formulation with Poly(propylene imine) Dendrimers with Surface-Grafted Glycerol: Release Kinetics of trans-Cinnamaldehyde and Germination Inhibition Effects.

The Third-generation glycerodendrimer polypropylenimine (GD-PPI-3) can be used in an aqueous formulation of Cinnamomum zeylanicum essential oil (CEO). The purpose was to give an overview of this innovative method of retaining and releasing essential oils. The formulation consisted of 366 min stirring at 1735 rpm of the aqueous solution of 2 mM GD-PPI-3 with CEO. Some physicochemical properties of these formulations, as well as the release of trans-cinnamaldehyde, have been studied. A bimodal distribution and no concentration or aging effect were observed by optical microscopy. Moreover, the release kinetics showed the retention of volatile molecules in solution under various environmental conditions. The release profile was characterized by an initial burst followed by a steady release. The dendrimers allowed us to reduce this initial burst and extended the release by at least 15 h. In addition, the herbicidal effect was evaluated: inhibition of Arabidopsis thaliana seed germination was obtained for 7 days with a formulation of 12.5 mg/L CEO in a closed space and 360 mg/L CEO in an open space.

Essential Oil-Based Bioherbicides: Human Health Risks Analysis.

In recent years, the development of new bio-based products for biocontrol has been gaining importance as it contributes to reducing the use of synthetic herbicides in agriculture. Conventional herbicides (i.e., the ones with synthetic molecules) can lead to adverse effects such as human diseases (cancers, neurodegenerative diseases, reproductive perturbations, etc.) but also to disturbing the environment because of their drift in the air, transport throughout aquatic systems and persistence across different environments. The use of natural molecules seems to be a very good alternative for maintaining productive agriculture but without the negative side effects of synthetic herbicides. In this context, essential oils and their components are increasingly studied in order to produce several categories of biopesticides thanks to their well-known biocidal activities. However, these molecules can also be potentially hazardous to humans and the environment. This article reviews the state of the literature and regulations with regard to the potential risks related to the use of essential oils as bioherbicides in agricultural and horticultural applications.

Use of New Glycerol-Based Dendrimers for Essential Oils Encapsulation: Optimization of Stirring Time and Rate Using a Plackett-Burman Design and a Surface Response Methodology.

Essential oils are used in an increasing number of applications including biopesticides. Their volatility minimizes the risk of residue but can also be a constraint if the release is rapid and uncontrolled. Solutions allowing the encapsulation of essential oils are therefore strongly researched. In this study, essential oils encapsulation was carried out within dendrimers to control their volatility. Indeed, a spontaneous complexation occurs in a solution of dendrimers with essential oils which maintains it longer. Six parameters (temperature, stirring rate, relative concentration, solvent volume, stirring time, and pH) of this reaction has been optimized by two steps: first a screening of the parameters that influence the encapsulation with a Plackett-Burmann design the most followed by an optimization of those ones by a surface response methodology. In this study, two essential oils with herbicide properties were used: the essential oils of Cinnamomum zeylanicum Blume and Cymbopogon winterianus Jowitt; and four biosourced dendrimers: glycerodendrimers derived from polypropylenimine and polyamidoamine, a glyceroclikdendrimer, and a glyceroladendrimer. Meta-analysis of all Plackett-Burman assays determined that rate and stirring time were effective on the retention rate thereby these parameters were used for the surface response methodology part. Each combination gives a different optimum depending on the structure of these molecules.

Identification of a Proanthocyanidin from Litchi Chinensis Sonn. Root with Anti-Tyrosinase and Antioxidant Activity.

This work follows an ethnobotanical study that took place in the island of Mayotte (France), which pointed out the potential properties of Litchi chinensis Sonn. roots when used to enhance skin health and appearance. Through in vitro testing of a crude methanolic extract, high anti-tyrosinase (skin whitening effect) and antioxidant activities (skin soothing effect) could be measured. HPLC successive bio-guided fractionation steps allowed the purification of one of the compounds responsible for the biological activities. The isolated compound was characterized by UV, IR, MS and 2D-NMR, revealing, for the first time in Litchi chinensis Sonn. roots, an A-type proanthocyanidin and thus revealing a consensus among the traditional use shown by the ethnobotanical study, in vitro biological activities and chemical characterization.

Encapsulation of Essential Oils for the Development of Biosourced Pesticides with Controlled Release: A Review.

Essential oil (EO) encapsulation can be carried out via a multitude of techniques, depending on applications. Because of EOs' biological activities, the development of biosourced pesticides with EO encapsulation is of great interest. A lot of methods have been developed; they are presented in this review, together with the properties of the final products. Encapsulation conserves and protects EOs from outside aggression, but also allows for controlled release, which is useful for applications in agronomy. The focus is on the matrices that are of interest for the controlled release of their content, namely: alginate, chitosan, and cyclodextrin. Those three matrices are used with several methods in order to create EO encapsulation with different structures, capacities, and release profiles.