# Green Extraction of Valuable Compounds from Rubber Seed Trees: A Path to Sustainability
## 7 Green Extraction of Rubber Seed Oil
### Ultrasound Assisted Extraction (UAE)
#### 7.3.2 Current Extraction on Rubber Seed Trees by UAE  
Rubber seed trees, a significant byproduct of the global seafood industry, have garnered increasing attention in recent years due to their rich content of valuable bioactive compounds. These compounds, which include phytochemicalal tocopherols, proteins, lipids, and various antioxidants, have the potential for use in diverse industrial applications, ranging from food and pharmaceuticals to cosmetics and wastewater treatment. However, the efficient extraction of these bioactivities from rubber seed trees poses a considerable challenge. UAE, a novel and eco-friendly technique, has emerged as a promising method for enhancing the extraction of bioactive compounds from rubber seed trees. UAE utilizes high-frequency sound waves to induce cavitation in the extraction medium, leading to microscale disturbances that improve mass transfer and facilitate the release of target compounds from the complex matrix of rubber seed trees [93]. This approach offers several advantages over traditional extraction methods, including reduced extraction times, lower solvent consumption, and improved yields. In recent years, researchers and industries alike have been exploring the potential of UAE to extract valuable bioactivities and production of biodiesel from rubber seed trees efficiently [113]. This growing body of research aims to optimize UAE parameters, such as frequency, power, time, and solvent composition, to maximize extraction yields while minimizing energy consumption and environmental impact [93]. Furthermore, the extracted bioactive compounds have been the focus of numerous studies aiming to evaluate their functional properties and potential applications in various sectors. The increasing demand for oil, coupled with the dwindling supply of traditional sources, has led to a growing interest in alternative, non-food feedstocks for the production of bio-based fuels. This study focuses on utilizing rubber seeds, sourced from rubber tree plantations, as a biomass feedstock for bio-oil production. Rubber seeds are attractive for this purpose as they are non-edible and are typically considered waste in rubber tree plantations. The oil extraction process begins with the preparation of rubber seed kernels, which involves oven drying at 100 \({}^{\circ}\)C for 24 h, followed by powdering and an additional drying step at 105 \({}^{\circ}\)C for 4 h. Following the characterization of the biomass, an optimization study is conducted using Design Expert 7.0 software, employing a central composite design within the response surface methodology framework. To expedite the extraction process,ultrasonication technology is utilized, significantly reducing the extraction time from the conventional method of at least 8 h to just 15 min. The optimized conditions for rubber seed oil (RSO) extraction are determined to be as follows: 15 g of biomass, a 5:1 n-hexane-to-biomass (mL g\({}^{-1}\)) ratio, a 50 \(\upmu\)m resonance amplitude, and a temperature of 60 \(\pm\) 5 \({}^{\circ}\)C, all within a 15 min reaction time. Under these conditions, the study achieves an impressive RSO yield of 30.3% \(\pm\) 0.3%. The extracted RSO exhibits favorable properties for use as a biofuel source, including a density of 0.89 g mL\({}^{-1}\) at room temperature, a kinematic viscosity of 26.7 cSt at 40 \({}^{\circ}\)C, and a high heating value of 39.2 MJ kg\({}^{-1}\). Furthermore, Fourier Transform Infrared Radiation spectroscopy analysis of the RSO at the optimum conditions reveals the presence of functional groups such as carboxylic acid and ester carbonyl. These functional groups are promising indicators of the potential suitability of RSO as a source for biodiesel production. In summary, this study demonstrates the feasibility of utilizing rubber seeds, often considered waste, as a valuable non-food biomass feedstock for the production of bio-oil.