**1. Introduction**

Natural products from cinnamon plants (*Cinnamomum* spp., Lauraceae) exhibit various bioactivities, such as antimicrobial, insecticidal, anti-inflammatory, antidiabetic activities and, etc. [1–5]. *Cinnamomum osmophloeum* Kanehira is commonly used as folk medicines and food flavors. It is scientifically reported that extracts and essential oils of *C. osmophloeum* exhibit the antioxidant, antibacterial, anxiolytic, xanthine oxidase inhibitory effects, and so forth [6–9].

Parts of natural plant products, especially essential oils, are highly volatile in the ambient environment and, therefore, may result in thermal oxidation/degradation. Microencapsulation or nanoencapsulation of the essential oils and extracts could provide protection and enhance the stabilization [10–12]. Encapsulation materials used include gelatin, cyclodextrins, gum arabic, caseinates, alginates, cellulose derivatives, chitosans, etc. [13–16]. Properties of natural plant products after microencapsulation would be influenced by the kinds of core-shell structures and coating materials [17–20].

Cyclodextrins are amphiphilic hollow cyclic oligosaccharides and form the inclusion complexes with versatile molecules [17,21,22]. β-Cyclodextrin, composed of seven α-D-glucopyranose units, is the most common cyclodextrin product and of good durability; it is a multifunctional encapsulation material to keep the bioactive ingredients from volatilization, oxidization, and etc. [23–25]. Many researchers have reported the microencapsulation of the bioactive constituents, essentials oil, or supercritical fluid extracts with β-cyclodextrin [9,10,26,27]. Ramos et al. proved that the inclusion of isopulegol, an alcoholic monoterpene, in β-cyclodextrin is an effective method to improve its antiedematogenic and anti-inflammatory activities [28]. Cyclodextrins are appropriate carriers

**Citation:** Chang, H.-T.; Lin, C.-Y.; Hsu, L.-S.; Chang, S.-T. Thermal Degradation of Linalool-Chemotype *Cinnamomum osmophloeum* Leaf Essential Oil and Its Stabilization by Microencapsulation with β-Cyclodextrin. *Molecules* **2021**, *26*, 409. https://doi.org/10.3390/molecules 26020409

Academic Editors: Marina Isidori, Margherita Lavorgna and Rosa Iacovino Received: 24 December 2020 Accepted: 13 January 2021 Published: 14 January 2021

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for delivering or releasing natural products in the pharmaceutical, food and cosmetic industries [16,29–33].

The aims of this study were to investigate the thermal degradation of linalool-chemotype *C. osmophloeum* leaf essential oil, find the optimal reaction conditions of microencapsulation of leaf essential oil with β-cyclodextrin, and evaluate the stabilization of leaf essential oil microcapsules. Through our research, it is expected to reveal the changes in the chemical structure of linalool during thermal decomposition and properly preserve the linaloolchemotype *C. osmophloeum* leaf essential oil by microencapsulating with β-cyclodextrin.
