Bioactive Compounds in Tea: Emerging Trends in Their Extraction and Application

Tea (Camellia sinensis), particularly prominent in China as the largest producer, is rich in bioactive compounds like polyphenols (including flavonoids and catechins), theanine, and caffeine, known for their antioxidant, anti-inflammatory, and health-promoting properties. However, conventional extraction methods often lead to degradation, poor yield, and low bioavailability of these compounds, limiting their applications. Despite extensive research on tea bioactives, a comprehensive understanding of how emerging green extraction technologies improve yield, stability, and functionality across various application domains remains limited. This review aims to fill this gap by systematically evaluating the efficiency, mechanisms, and applicability of these advanced extraction methods based on the past five years of studies. Recent advances focus on optimizing green extraction techniques to overcome these challenges. Methods such as Supercritical Fluid Extraction (SFE) (temperature 35 to 60 °C, co-solvent 5 to 10%, and time 90 min) show superior yields (e.g., 25% higher Epigallocatechin gallate (EGCG)) and purity, Ultrasound-Assisted Extraction (UAE) (frequency 20 to 40 kHz, time 10 to 30 min) increases catechin yield by 30%, and Microwave-Assisted Extraction (MAE) offers improved efficiency compared to traditional techniques. Enzyme-Assisted Extraction (EAE) and Pulsed Electric Field (PEF) extraction also offer promising, sustainable alternatives. These extracted bioactives find growing applications in functional foods/beverages (acting as nutraceuticals and natural preservatives), cosmetics (via nanotechnology for enhanced efficacy), and pharmaceuticals (e.g., encapsulated EGCG for inflammation). By integrating recent developments and highlighting practical limitations, this review provides insights into the selection and optimization of green extraction methods for industrial applications. Despite progress, key challenges persist, including optimizing bioavailability and ensuring the scalability and environmental sustainability of advanced extraction methods.