The essential oil of Callistemon viminalis (EOC) is rich in monoterpenes that present a wide range of biological properties, including antibacterial, antifungal, insecticidal, and antioxidant activities. However, applications of EOC are limited by its volatility and low solubility in water. The formation of inclusion complexes (ICs) with cyclodextrins (CDs) offers a way to improve the characteristics of unstable substances such as EOC. Therefore, the aim of this work was to characterize and analyze the composition of EOC, to complex it with β-CD using a kneading technique, and to perform controlled release assays. The formation of the IC was observed using infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Molecular dynamics was performed to analyse the interaction of β-CD with the majority compounds present in the EOC. The IR spectra and the results of the DSC and TGA calorimetric analyses showed that the physicochemical characteristics of the IC were different to those of the free EOC. The XRD and SEM analyses revealed structural and morphological changes after IC formation, hence confirming that complexation had occurred. In the case of the free EOC, 86% had been released after 2 days of dialysis, while the IC showed 65% release of the oil after 8 days, indicating that formation of the EOC/β-CD inclusion complex was effective in retarding the release of the EOC.Theoretical data showed that the most stable IC was obtained with α-terpineol, one of the major components of EOC. The results suggested that the activity of the IC should be evaluated in existing EOC applications.

中文翻译：

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经揉捏法制得的苦参精油包合物

Callistemon viminalis (EOC) 的精油富含单萜，具有广泛的生物学特性，包括抗菌、抗真菌、杀虫和抗氧化活性。然而，EOC 的应用受到其挥发性和在水中的低溶解度的限制。与环糊精 (CD) 形成包合物 (IC) 提供了一种改善不稳定物质 (如 EOC) 特性的方法。因此，这项工作的目的是表征和分析 EOC 的组成，使用捏合技术将其与 β-CD 复合，并进行控释分析。使用红外光谱 (IR)、差示扫描量热法 (DSC)、热重分析 (TGA)、X 射线衍射 (XRD) 和扫描电子显微镜 (SEM) 观察 IC 的形成。进行分子动力学以分析 β-CD 与 EOC 中存在的大多数化合物的相互作用。红外光谱以及 DSC 和 TGA 量热分析的结果表明 IC 的理化特性与游离 EOC 的不同。XRD 和 SEM 分析揭示了 IC 形成后的结构和形态变化，从而证实发生了络合。在游离 EOC 的情况下，透析 2 天后释放了 86%，而 IC 显示在 8 天后释放了 65% 的油，表明 EOC/β-CD 包合物的形成有效地阻止了EOC 的释放。理论数据表明，最稳定的 IC 是用 α-萜品醇获得的，α-萜品醇是 EOC 的主要成分之一。