Highly Concentrated Emulsions Containing High Loads of Pterostilbene

Abstract

Pterostilbene is a highly researched molecule due to its bioactivity. However, its hydrophobicity limits its application. For this reason, researchers have sought to encapsulate pterostilbene (namely, in oil-in-water emulsion) to increase its availability. Studies are lacking when it comes to the effects of pterostilbene and its concentration at the oil/water interface. This paper discusses the effects of oil types, storage temperature, and pterostilbene concentration on the stability of the emulsions, as well as the interactions between encapsulated pterostilbene and the oil and water phases. Results showed that pterostilbene is present at the oil/water interface, affecting the interfacial tension and consequently the droplet size. It was also shown that encapsulation efficiency is affected by the storage temperature and oil type. Finally, it was proven that, according to oil types and storage temperature, the stability of pterostilbene to light is affected.

Introduction

Pterostilbene (tran-3,5-dimethoxy-4′-hydroxystilbene), noted hereafter Pts, is a stilbenoid found naturally in the leaves of grapevine, sandalwood, and heartwood, as well as in blueberries, bark of Guibourtia tessmannii, grapes, and Vaccinium berries. (1−8) Some of the bioactivities associated with it exhibit antioxidant, anti-inflammatory, antiaging, anticancer, antitumorigenic, cardio-protective, antidiabetic, and neuroprotective properties. (1−8) However, it remains a difficult molecule to handle due to its hydrophobicity and sensitivity to light and air. More specifically, Pts oxidizes turning trans-Pts into cis-Pts, the latter being an isomer with reported high bioactivity. (5,9)

A quick literature search (Scopus) shows that in the last 22 years, about 1300 studies were done on Pts, 800 of which in the last 5 years alone. The main field of studies remains in biology, pharmacology, and medicine. However, the literature available is limited when searching for publications that have specifically studied the encapsulation of Pts. Table 1 focuses on these specific articles and details the findings of these studies: the type of encapsulating system and the main reported properties (size amount of Pts if available). In most of these studies, the particles encapsulating Pts have a size in the nanometric range, to improve bioavailability, and the concentrations of Pts encapsulated are low. Only one study reported that Pts is most soluble in medium chain triglyceride (MCT) oil, prepared emulsions containing 10.4% Pts of the total emulsion, and the antioxidant activity and bioavailability of Pts were evaluated. (7)

Emulsions with high concentrations of Pts and high oil fractions are important for applications like biopesticides where the goal is to formulate a concentrated emulsion that will be diluted by the farmer just before application. Since the dilution has to be in water, stable highly concentrated oil-in-water emulsions are needed. Furthermore, nanometric oil droplet sizes are not required for this kind of application, which make the encapsulation techniques reported in the literature not relevant. To the author’s knowledge, no studies have been carried out studying the effects of the ingredients used to prepare the emulsions, the interactions between these ingredients and Pts, and the concentration of Pts on the stability of emulsions and encapsulation efficiency. This kind of study is crucial to detect the stability limits of Pts-concentrated emulsions.

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Materials

For the emulsions, medium chain triglyceride (MCT) oil (Labrafac CC) was gratefully provided by Gattefossé SAS (France), and coconut oil, vitamin E (α-tocopherol), and Tween 20 were purchased from Sigma-Aldrich. Pts was purchased from iChemical (China).

Highly Concentrated Emulsions Containing High Loads of Pterostilbene, Wael Kaade*, Sara Rubio, Achille Bogas-Droy, Valentine de Villedon, Eric Laurichesse, and Veronique Schmitt, Cite this: ACS Omega 2023, Publication Date:July 12, 2023, https://doi.org/10.1021/acsomega.3c01861, © 2023 The Authors. Published by American Chemical Society

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