Optimization of Extraction Process and Component Analysis of Grass Fruit Essential Oil
Amomum tsao ko is a perennial herbaceous plant of the ginger family and the cardamom genus. It is a traditional medicinal and edible plant in China, mainly distributed in Yunnan, Guizhou, Sichuan, and western Guangxi. The fragrance of grass and fruit has been repeatedly used in epidemic prevention prescriptions in recent years, as it helps to cleanse the body, dispel dampness, and invigorate the spleen. In the TCM treatment plan of Diagnosis and Treatment Plan for novel coronavirus Pneumonia, the light, ordinary and heavy prescriptions all have the application of Caoguo. The initial clinical prescription usage rate reached 46.43%, and the mid-term clinical prescription usage rate reached 24.00%, making it one of the drugs with high frequency of use. Grass fruit is rich in various chemical components with pharmacological effects, mainly volatile oils, as well as phenols, steroids, etc. The volatile essential oil of grass fruit, as the main active substance of grass fruit, mainly includes compounds such as phenylpropanoids, sesquiterpenes, monoterpenes, and fatty acids, which have pharmacological effects such as antioxidant, antibacterial, anti-tumor, antiviral, anti asthmatic, and expectorant.

Common methods for extracting essential oil from grass fruit include microwave-assisted extraction, supercritical carbon dioxide extraction, organic solvent extraction, ultrasound assisted extraction, steam distillation, etc. The most representative microwave-assisted extraction method is the microwave solvent-free extraction method, which optimizes the extraction process of grass fruit essential oil by examining conditions such as microwave power, microwave radiation time, and extraction temperature. Although this method has the advantages of short extraction time and low energy consumption, it also has the problem of difficulty in achieving industrialization. Supercritical CO2 extraction usually requires consideration of factors such as extraction pressure, extraction temperature, extraction time, CO2 flow rate, etc., and has high equipment requirements. The steam distillation method is the most commonly used method for extracting essential oil from grass fruit, which is simple, safe, and suitable for extracting volatile components with high boiling points that are insoluble or slightly soluble in water. Ultrasonic assisted method is usually combined with organic solvent extraction method, known as ultrasonic (assisted) organic solvent extraction method. The optimal process parameters are screened by examining the type of extraction solvent, ultrasonic power, extraction time, and extraction temperature. To determine the optimal extraction conditions, various methods are often used for optimization in research. In recent years, the response surface methodology (RSM) model has been the most commonly used, and a large amount of data has been obtained through experimental design and practical operation. The optimal conditions are determined by fitting the function and establishing the model through multiple quadratic linear regression equations. With the development of algorithms, backpropagation artificial neural network (BP-ANN) models have become powerful tools for optimizing extraction processes due to their excellent fitting, accuracy, and predictive ability. This model can handle noisy and missing data well and can learn from experimental data. The BP-ANN model has high accuracy in predicting extraction rates and strong optimization ability in fitting experimental data; It has unparalleled advantages over RSM models in multi factor and multi-level optimization experiments. By combining genetic algorithm (GA), global optimization can be achieved to obtain the optimal process conditions. Previous studies have rarely used BP-ANN method to optimize the extraction process of grass fruit essential oil. This optimization method can provide theoretical reference for subsequent related work.

This study used steam distillation and ultrasonic organic solvent method to extract essential oils from grass fruit. In this experiment, the essential oil extractor used for extracting grass fruit essential oils by steam distillation was improved to lower the temperature of the condensing part during the extraction process. By conducting single factor experiments, optimizing extraction conditions using RSM and BP-ANN, and comparing the optimized models, the optimal process parameters were obtained to provide data support for the efficient extraction and precise application of grass fruit essential oil; By analyzing the composition of essential oil in Caoguo using gas chromatography-mass spectrometry (GC-MS), exploring its pharmacological substance basis, and promoting the modern application of traditional Chinese medicine Caoguo.

The steam distillation method and ultrasonic organic solvent method were used and compared to extract grass fruit essential oil. The extraction conditions of grass fruit essential oil were optimized by single factor, RSM, and BP-ANN. The optimal process parameters for steam distillation and ultrasonic organic solvent method were soaking time of 53.00min, distillation time of 72.00min, liquid-solid ratio of 11.00mL/g, ultrasonic power of 150W, ultrasonic time of 27min, liquid-solid ratio of 6.3mL/g. Under these conditions, the extraction rates of grass fruit essential oil were 1.59% and 3.70%, respectively. The experimental results show that compared with the RSM model, the BP-ANN model has better performance in both optimization ability and prediction accuracy, and can significantly improve prediction ability and stability. It has high feasibility and obvious advantages in handling multi factor problems.
The components of grass fruit essential oil extracted by steam distillation and ultrasonic organic solvent method were identified and compared by GC-MS, with 34 and 43 types, respectively. Among them, 1,8-eucalyptol was found to have higher content, as well as α – carvacene, 4-propylbenzaldehyde, trans citral, trans-2-decenal, α – terpineol, cis citral, β – pinene, trans geraniol, cis geraniol, acetate geraniol, (-) -4-terpineol, etc. Its main component, 1,8-eucalyptol, may be an important basis for its pharmacological effects such as antibacterial, anti-tumor, and antiviral effects. It has a high content in grass fruit essential oil and has great potential for development. Research has shown that grass fruit essential oil can interact with SARS-CoV-2 spike protein RBD in aerosols, block the interaction between RBD and hACE2, inhibit their binding to receptors, cut off transmission pathways, and have great potential in blocking virus aerosol transmission. This study can provide new ideas for the further development and utilization of grass fruit essential oil, promote its application innovation, and broaden its path towards modernization of traditional Chinese medicine.