Development of essential oils inclusion complexes: a nanotechnology approach with enhanced thermal and light stability

Discover Nano Research Development of essential oils inclusion complexes: a nanotechnology approach with enhanced thermal and light stability Fernanda Ramalho Procopio1 · Ramon Peres Brexó1 · Luis Eduardo Sousa Vitolano1 · Maria Eduarda da Mata Martins2 · Maria Eduarda de Almeida Astolfo3 · Stanislau Bogusz Junior3 · Marcos David Ferreira1 Received: 15 April 2024 / Accepted: 28 November 2024 © The Author(s) 2024  OPEN Abstract Essential oils (EOs) are volatile compounds that may have antimicrobial and antioxidant properties. Despite their potential application, low water solubility and chemical instability are limiting factors. Nanoencapsulation processes can overcome this problem, protecting against external factors and promoting a moderate release. Therefore, the objective of the present study was to encapsulate Cymbopogon citratus (CC) and Origanum vulgare (OV) essential oils in β-cyclodextrin (βCD) complexes. Different ratios (w/w) between βCD and EOs (96:4, 92:8, 90:10, 88:12) were tested, seeking greater entrapment efficiency. The particles were characterized by yield, entrapment efficiency, size distribution, morphology, crystallinity, infrared spectroscopy, and thermal behavior. Furthermore, the thermal (70 °C) and photochemical (UV) stability of the free and encapsulated EO was evaluated for 48 h. The results showed that the βCD-CC 90:10 and βCD-OV 90:10 formulations presented greater entrapment efficiency. Crystalline structures of varying sizes (200 to 800 nm), trapezoidal shape, and tendency to aggregation were obtained. Changes in the βCD crystalline organization and the suppression of characteristic free oil absorption bands suggest the EO entrapment. Regarding stability results, βCD-CC remained constant when CC showed losses of 20% (photodegradation) and 60% (thermal degradation) after 48 h of stress exposure. Free OV showed slight variations in absorbance over time, while βCD-OV remained constant over 24 h (thermal degradation) and maintained 60% of oil over 48 h of photo exposure. Furthermore, OV and CC demonstrate color change over time, while βCD-OV and βCD-CC remained constant. The results demonstrate that nanoencapsulation can be an interesting tool for protecting EOs. Keywords Inclusion complexes · Thermal analysis; bioactivity Supplementary Information The online version contains supplementary material available at https://doi.org/10.1186/s11671-024- 04158-7. * Fernanda Ramalho Procopio, | 1Brazilian Agricultural Research Corporation, Embrapa Instrumentation, São Carlos, SP 13561‑206, Brazil. 2Institute of Biosciences, Humanities and Exact Sciences, São Paulo State University (UNESP), São José Do Rio Preto, Brazil. 3São Carlos Institute of Chemistry (IQSC), University of São Paulo (USP), São Carlos, São Paulo 13566‑590, Brazil. Discover Nano (2024) 19:198 | https://doi.org/10.1186/s11671-024-04158-7 Vol.:(0123456789) Research Discover Nano (2024) 19:198 | https://doi.org/10.1186/s11671-024-04158-7 1 Introduction The use of essential oils (EOs) as control agents in the agroindustry has been widely studied due to the varied composition of terpenes, aldehydes, alcohols, and phenols [1]. These compounds may have antioxidant, anti-inflammatory, antibacterial, antifungal, and insecticidal activity, arousing interest in the agricultural, food, and pharmaceutical industries. They appear as an alternative to synthetic additives, increasingly presenting undesirable side effects [2, 3]. Origanum vulgare (OV) and Cymbopogon citratus (CC) stand out in antifungal action due to their carvacrol/thymol and geranial/neral primary compounds, respectively [4]. Each oil’s mechanisms and effectiveness are directly related to its chemical composition and, consequently, its stability. The compounds are susceptible to external factors such as temperature, oxygen, and light, and their bioactivity may be impaired [5]. Therefore, different strategies have been applied to improve stability and facilitate the incorporation of these extracts. Combining nanotechnology strategies for incorporating essential oils can facilitate their application in foods, enhancing their properties. In general, micro or nanoencapsulation processes allow the packaging of bioactive compounds, seeking protection against external factors such as temperature, pH, oxygen, and interaction with other compounds [6]. The advantage of obtaining nanoscale particles is the increase in the surface area/volume ratio. In this way, more active sites are available, improving the encapsulated compound’s bioavailability and consequently allowing greater interaction with enzymes and microorganisms [7]. Cyclodextrins (CD) are cyclic oligosaccharides composed of glucopyranose units linked by α-1,4 glycosidic bonds. The most common are α-cyclodextrin (six units), β-cyclodextrin (seven units), and γ-cyclodextrin (eight units). β-cyclodextrin (βCD) is the most used due to its ease of obtaining through synthesis, manufacturing, or extraction processes from natural sources [8]. The conical three-dimensional structure of CD molecules, with an internal cavity of lower polarity than water, is a key feature [6]. This structure allows for the retention of hydrophobic molecules such as essential oils in the internal cavity, leading to improved solubility in aqueous media. These properties make CDs suitable for a wide range of applications, including drug and pesticide delivery systems, flavor encapsulation, odor control, improving chemical stability and solubility, pollutant removal, and smart food packaging [9–11]. However, it is important to note that studying the most appropriate active and carrier ratio is necessary when forming essential oil inclusion complexes in CDs. Typically, an increase in this ratio can lead to a decrease in entrapment efficiency [12]. Nevertheless, CDs are considered nanoencapsulation agents, and the efficiency of the process is directly related to the stoichiometry and polarity of host and guest molecules [11]. Nanoencapsulated essential oils can promote a moderate release of compounds, prolonging antimicrobial activity with less sensorial impact on the food product [1, 13]. Ebrahimi et al.[14] observed a delay in ripening and microbial counts of pears when applying gluten-based coatings with cellulose nanoparticles containing oregano essential oil. Nevertheless, few studies have evaluated the efficiency of the encapsulation method on the stability of oils with different compositions. In the study by Barbieri et al.[5], different Lippia graveolens chemotypes were encapsulated in β and γ-cyclodextrins (β-CD and γ-CD). The authors observed that oils rich in carvacrol and thymol showed the strongest affinity for γ-cyclodextrin, while those with β-caryophyllene presented higher encapsulation efficiency in β-cyclodextrin. In contrast, after 14 days of storage, carvacrol concentration in the β-CD complex remained constant, while in the γ-CD complex, the concentration was significantly reduced (...truncated)