Comparison of the efficiency of combined Sono-Clevenger system and Clevenger system in extracting Pimpinella anisum essential oil

Extended Abstract
Introduction: Anise (Pimpinella anisum L.), commonly known as Roman anise or Badian, is an annual herbaceous plant belonging to the Apiaceae (Umbelliferae) family and has been recognized as one of the oldest medicinal plants. This plant grows to a height of 30–50 cm and produces small white flowers arranged in compound umbels, along with greenish-yellow fruits that are pointed at the apex with five prominent ridges. According to traditional Iranian medicine, anise seeds possess a warm and dry nature and have been used for the prevention and treatment of various diseases. The seeds, especially when fresh and unpeeled, are the primary part used for medicinal and aromatic purposes. Major essential oil constituents include anethole (~81%), methyl chavicol, linalool, himachalene, and alpha-terpineol.
Anise essential oil is applied in pharmaceuticals and cosmetics to improve respiratory function, as an ingredient in perfumes and soaps, and topically to enhance drug penetration through the skin. Efficient extraction methods are crucial due to the high value of essential oils. Conventional techniques like hydro-distillation and solvent extraction often show limitations such as low yield, long extraction time, high energy consumption, loss of thermolabile compounds, and potential solvent residues. Consequently, green and sustainable extraction technologies have gained attention.
Modern extraction methods such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), supercritical fluid extraction, rapid distillation, and subcritical water extraction offer advantages including shorter processing time, reduced solvent consumption, and lower environmental impact. UAE, in particular, has received significant interest due to cavitation effects that enhance solvent penetration, mass transfer, and extraction efficiency at lower temperatures, preserving heat-sensitive compounds like phenolics. Previous studies have shown that ultrasound significantly affects essential oil yield depending on power, duration, and mode. For example, Thakker et al. (2018) applied ultrasound-assisted hydro-tropic extraction (UAHE) to isolate geraniol from Cymbopogon martini leaves, optimizing amplitude, pulse cycles, and extraction parameters. Liu et al. (2019) optimized Sono-Clevenger conditions for Iberis amara seeds and demonstrated improved efficiency compared to conventional hydro- and steam-distillation. Hamza Alasalvar et al. (2021) showed effective and sustainable extraction of phenolic antioxidants from Lavandula angustifolia, and Bahmani et al. (2015) observed that ultrasound pretreatment enhanced tarragon leaf essential oil yield, with sonication time having a significant effect.
Considering the wide applications of anise essential oil in food, pharmaceutical, and healthcare industries, this study aimed to investigate efficient extraction methods using conventional Clevenger hydro-distillation and a newly designed ultrasound–Clevenger system. The study compared extraction yield, energy consumption, and physicochemical properties of essential oils. The novelty of this work lies in the application of continuous and pulsed ultrasound at different powers and durations to reduce energy consumption while preserving essential oil quality.
Materials and Methods
Sample Preparation
Anise seeds used in this study were obtained from Pakkan Seed Company, Isfahan, Iran. The seeds were ground using a mechanical grinder (Nosh Shekan, Khorasan, Iran). For each experiment, 25 g of ground seeds were used.
Essential Oil Extraction Using Clevenger Apparatus
For hydro-distillation using a conventional Clevenger apparatus, 25 g of ground anise seeds were transferred into a 1000 mL round-bottom flask and mixed with 500 mL of distilled water. The flask was placed on a heater and connected to a Clevenger apparatus, which was fixed on a metal stand using clamps. Distilled water was added to the graduated arm, and the inlet was sealed with cotton wool. The start time was recorded at the appearance of the first essential oil drop. After 180 min, the extracted oil was measured from the graduated arm, transferred into a vial, dried over anhydrous sodium sulfate, and the weight was recorded. Vials were sealed with foil and Parafilm and stored at 4°C until analysis.
Ultrasound–Clevenger System
The ultrasound–Clevenger system was designed to simultaneously apply ultrasonic waves and Clevenger distillation. The probe dimensions were measured and a preliminary design was created using SolidWorks 2016. The Teflon-coated ultrasonic probe was inserted into the flask to a depth of 2 cm to ensure proximity to the bottom .
 Essential Oil Extraction Using Ultrasound–Clevenger
In this method, 25 g of ground sample was mixed with 500 mL of distilled water in the two-necked flask. Extractions were performed at three ultrasonic power levels (200, 350, and 500 W), three sonication durations (20, 40, and 60 min), a fixed frequency of 20 kHz, and three pulse modes (continuous, 2s off–2s on, 4s off–2s on). The selection of variable levels was based on literature, preliminary experiments, and experimental design. Ultrasonication was applied simultaneously with Clevenger distillation using a Swiss-made ultrasonic generator (AMMMP, M.P. Interconsulting) and an on–off ultrasonic device manufactured by Mafoqot Fanavari Co.
Essential Oil Yield
For the conventional Clevenger method, the extraction was stopped after 180 min. For the ultrasound–Clevenger method, the extraction was stopped at the time indicated in the experimental design (Table 1) from the appearance of the first essential oil drop. The total collected oil was measured volumetrically and expressed in mg per 25 g of ground seeds.
Energy Consumption
Energy consumption during each experiment was measured using a power meter (UT230B-EU, UNI-T, China). The results from both methods were compared.
Chemical Composition
Quantitative and qualitative analyses of major essential oil components including anethole, estragole, zingiberene, and γ-himachalene were performed using GC–MS at the Medicinal Plants Research Center, Jahad University, Tehran. The analysis was conducted using an Agilent 6890 GC system with a BPX5 column (30 m × 0.25 mm i.d., 0.25 μm film thickness). One microliter of n-hexane-diluted sample was injected. The oven temperature program was as follows: 50 °C for 5 min, ramp at 3 °C/min to 240 °C, then 15 °C/min to 300 °C with a 3-min hold. Injector temperature was 290 °C, split ratio 1:35, helium carrier gas flow 0.5 mL/min. Mass spectra were recorded using an Agilent 5973 MS with electron ionization at 70 eV, ion source at 220 °C, scanning from 40–500 m/z. Data were processed using ChemStation software.
Statistical Analysis
Data were analyzed and optimized using response surface methodology (RSM) with a Box–Behnken design (BBD) in Design Expert 12. Independent variables included ultrasonic power, extraction time, and pulse mode, while dependent variables were essential oil yield and energy consumption. Optimization was performed at a 95% confidence level.
Results and discussion: The essential oil yield of anise seeds was compared between Sono-Clevenger and conventional Clevenger methods. Results indicated that the ultrasound-assisted method achieved comparable yields in a shorter time. ANOVA showed that extraction time significantly affected the yield (P < 0.05), while power and pulse mode had minor effects. The pulse mode (4 s off–2 s on) improved mass transfer by creating cyclic high-intensity peaks, facilitating better release of essential oil at lower powers (Aguiló-Aguayo et al., 2017).
Energy Consumption: Energy use was significantly reduced with Sono-Clevenger. ANOVA confirmed extraction time as a significant factor, while ultrasonic power had no significant effect. The linear model showed good fit (R2 = 0.7362), indicating reliable prediction of energy consumption.
Statistical Analysis and Optimization: The models were validated using RSM with Box–Behnken design. The optimal condition was 200 W, 20 min, and pulsed mode 4s off–2s on. Validation experiments confirmed the predicted essential oil yield (166.79 mg/25 g seeds) and energy consumption (0.896 kWh).
GC–MS Analysis: Chemical profiling showed anethole as the main component (92.89% in Sono-Clevenger vs. 89.9% in Clevenger). Other major compounds like estragole, γ-himachalene, and zingiberene were higher in the ultrasound-assisted extraction, indicating better preservation and release of key bioactive compounds.
In summary, the Sono-Clevenger system improved extraction efficiency, reduced energy consumption, and maintained essential oil quality compared to conventional hydro-distillation.
Conclusion: The study demonstrated that the ultrasound-assisted Clevenger (Sono-Clevenger) method enhanced essential oil extraction from anise seeds compared to conventional hydro-distillation. Optimal conditions (200 W, 20 min, 4s off–2s on) provided higher yield, better preservation of bioactive compounds such as anethole, estragole, γ-himachalene, and zingiberene, and significantly reduced energy consumption. Statistical analysis validated the model and confirmed reliability of predictions. Sono-Clevenger offers a rapid, energy-efficient, and effective extraction technique, making it suitable for industrial applications in food, pharmaceutical, and cosmetic sectors.