## 1 Introduction  
Star anise (_Illicium verum_) essential oils (SAEOs) are widely used in cosmetics, food products, pharmaceuticals, and pesticides. They have effective antioxidant [1] and antibacterial [2] activities, prevent cancer [3], reduce inflammation [4], and repel insects [5]. The main components of SAEOs are aromatic compounds and terpen, which can be extracted by hydrodistillation (HD), steam distillation, solvent extraction (SE), and supercritical fluid CO\({}_{2}\) extraction. HD has a low extraction rate, high energy consumption, and a long extraction time [6]. [PERSON] et al. [7] indicated that star anise water extract exhibited moderate and selective cytotoxic effects against HepG2 cell lines compared with those of essential oil. Solvent extraction not only requires a low temperature but also residual organic solvents [8]. Compared with HD and solvent extraction, critical extraction, which has a higher yield, can protect the extract from thermal degradation and solvent pollution [9]. These methods are widely used in the extraction of essential oils [10].  
It has been reported that the bioactivity of essential oil is determined by its composition, which can be affected by extraction methods, solvent polarity, and extraction conditions [11; 12; 13; 14]. Marjoram essential oils containing 21% volatile oils extracted using supercritical CO\({}_{2}\) (SCD) and those containing 9% volatile oils extracted using Soxhlet ethanol showed significantly different antibacterial activities [15]. [PERSON] et al. [16] also found that the carrot essential oils obtained by the supercritical extraction method exhibited the strongest antibacterial effect against gram-positive bacteria, indicating that exploring suitable methods to extract essential oils is necessary.  
However, it is important to develop instruments with high sensitivity and speed for analysing essential oils. Electronic nose (E-nose), as an intelligent system equipped with a series of chemical sensors, has high sensitivity and a rapid analysis speed [17]. Gas chromatography-ion mobility spectrometry (GC-IMS) can also be used to characterise volatile compounds because of its high sensitivity characteristic. Both are widely used to discriminate between authenticity and adulteration because of their high sensitivity, rapid analysis, low cost, and ease of construction [18; 19; 20; 21]. [PERSON] et al. [22] combined an E-nose with chemometric approaches to distinguish between the authenticity and adulteration of sausages with soy protein. E-nose and GC-IMS are suitable for characterising essential oils extracted using diverse different extraction methods [23].  
Different extraction methods are used for a variety of applications. However, the cost performance greatly differs among essential oils that are extracted by different methods, thereby causing adulteration in the market. The present study mainly focused on the components and biological activities of essential oils extracted using different methods, whereas there are few references for rapid discrimination. Moreover, there are no rapid, low-cost techniques for the detection and quantitative assessment of essential oil products to avoid different types of fraud in the essential oil industry. Therefore, it is necessary to establish a rapid and highly sensitive method for detecting essential oils extracted by different methods. In this study, E-nose, GC-mass spectrometry (MS), and GC-IMS combined with principal component analysis (PCA) and linear discriminant analysis (LDA) were used to evaluate SAEOs extracted by HD, ethanol solvent extraction (ESE), SCD, and subcritical extraction (SE). This study aimed to establish the fingerprints of the volatile components of SAEOs extracted by the four methods and allow the realisation of effective quality control over adulterated or counterfeit essential oil products in the market.