Optimization of Extraction Process Model for Essential Oil from Changshan Pomelo Peel, Study on Chemical Composition and Antioxidant Activity

Changshan huyou (Citrus aurantium Changshan huyou) is a citrus plant in the Rutaceae family, mainly produced in Changshan County, Zhejiang Province. It grows in red soil areas that are tolerant to barrenness, cold, low hills, and gentle slopes. Its cultivation and breeding history has been over a hundred years. As a medicinal and edible plant, the peel and fruit of Changshan Hu pomelo can be used as medicinal parts. According to the Compendium of Materia Medica, pomelo has a sour and cold odor, is non-toxic, and has the functions of digestion, fresh alcohol toxicity, treating bad breath after drinking alcohol, removing gastrointestinal evil qi, treating pregnancy induced nausea and vomiting, and reducing oral weakness. As the main production area of Changshan pomelo in China, Changshan County in Zhejiang Province produces the best quality and good efficacy of Changshan pomelo. Changshan pomelo is also popular in the beverage and food processing industries due to its rich nutritional components such as amino acids, sugars, and vitamins, in addition to being a fruit. The main by-product of the production and processing of Changshan Huyou pomelo is the Changshan Huyou peridap (Citrus × aurantium Changshan huyou peridap, CP), which accounts for about 50% of the total weight of Changshan Huyou pomelo. Most of it is treated as waste residue and has not been fully utilized. Studies have shown that the peel of Changshan Huyou pomelo contains abundant volatile oil components, accounting for about 0.5% to 2.0% of the fresh weight of the peel. These volatile components have significant anti-inflammatory, antibacterial and antioxidant effects, and can be used as sources of food additives, spices, essence and natural preservatives. Therefore, in-depth research and development of CP are of great significance.
The extraction method of traditional Chinese medicine is the driving force behind the development of the Chinese medicine industry. The traditional extraction methods for plant volatile oils include steam distillation, microwave extraction, organic solvent extraction, pressing, supercritical CO2 extraction, subcritical fluid extraction, enzymatic hydrolysis, etc. At present, steam distillation is commonly used to extract essential oils from CP, which is low-cost, easy to operate, and pollution-free. It is the most commonly used extraction method for CP essential oils. According to existing research results, it has been found that the extraction rate of CP essential oil by steam distillation is approximately 0.4% to 1.28%, which is related to the variety, origin, and extraction conditions of Changshan Huyou. The steam distillation method has been widely used for extracting plant essential oils and is the preferred method for extracting volatile oils from medicinal and edible plants. In addition, a small number of studies have used methods such as pressing, organic solvent extraction, and supercritical CO2 extraction to extract CP essential oil, among which pressing has a long operating cycle and low oil yield; Although the organic solvent extraction method has a high extraction rate, it is difficult to separate organic solvents from essential oils, resulting in low purity of essential oils. Additionally, organic solvents generally have low boiling points and extremely high risk factors; Supercritical CO2 extraction method is costly.
This study used CP as the raw material and extracted CP essential oil by steam distillation. Through single factor experiments, response surface methodology (RSM) and artificial neural network (ANN) were applied to optimize the essential oil extraction process, and gas chromatography-mass spectrometry (GC-MS) was used to analyze its chemical composition. The aim is to provide a theoretical basis for the extraction and application of CP essential oil, and to provide technical and theoretical basis for the study of its physicochemical properties and comprehensive development and resource utilization.

This article systematically extracts essential oil components from CP using steam distillation and optimizes the extraction process. Firstly, the optimal powder particle size and pretreatment conditions for essential oil extraction were screened, and single factor screening experiments were conducted on three factors that have a significant impact on the extraction rate of CP essential oil: extraction time, extraction temperature, and liquid-solid ratio. Based on the results of single factor screening, two different methods, RSM and ANN, were used to further optimize the extraction conditions. RSM analysis found that the liquid-solid ratio has a significant impact on the extraction rate of CP essential oil. A too small liquid-solid ratio is not conducive to sufficient contact between the material and the solvent, resulting in a decrease in extraction rate; Excessive liquid-solid ratio can easily lead to resource waste, which cannot achieve the goal of low-energy and high-efficiency extraction, and is not suitable for practical applications. The fitting degree of various data in the ANN model has reached a high level, and there is a good correlation between the experimental values and the predicted values of the model. The predicted results are reasonable and reliable. Comparing the predicted values of the two methods with the experimental values, it was found that the difference between the predicted values of ANN and the experimental values was smaller and more superior. Based on this, the optimal extraction conditions for the ANN model were determined as follows: particle size of 24 mesh, soaking in distilled water for 1 hour, liquid-solid ratio of 34.86 mL/g, extraction temperature of 300.00 ° C, extraction time of 166.21 minutes, and CP essential oil extraction rate of 0.82%. The GC-MS analysis results of CP essential oil showed that it contains abundant terpenoids, mainly composed of D-limonene with a relative content of 47.56%, followed by β – cubane and γ – terpinene. In addition, the analysis of physicochemical properties and antioxidant activity shows that the CP essential oil extracted by steam distillation has good stability and antioxidant activity, and can be used as a natural source of antioxidants and preservatives.
Against the backdrop of the country’s vigorous development of traditional Chinese medicine, the unique variety of Changshan Huyou has not yet been fully researched and developed. CP, as the main byproduct generated from the processing and production of Changshan Huyou, contains abundant essential oil components and has important development and utilization value. This study aims to optimize the extraction process of CP essential oil and investigate its chemical composition and physicochemical properties. It can provide a new approach for the rational utilization of waste resources of Changshan pomelo and is of great significance for promoting the in-depth development of natural active ingredients in the peel of Changshan pomelo. The research results were published in the 7th issue of Natural Product Research and Development in 2024