Effects of Autohydrolysis on the Phenolic Extraction and Antioxidant Capacity of Camellia sp. Seed Husk Extracts

The Camellia genus stands out as one of the most prevalent plant groups across Asia. Its exquisite flowers, valued as adornments, and its role in tea production have led to a surge in cultivating plants from this genus, notably focusing on Camellia sinensis, in recent years. However, this escalated cultivation has inadvertently led to a rise in by-product generation, potentially exerting detrimental effects on the environment. To mitigate this, strategies for waste reduction are imperative. Thus, it becomes essential to embrace novel principles of bio-refinery and circular bioeconomy, prioritizing the utilization of natural resources like eco-friendly solvents and residual biomass. This study homes in on the husk of Camellia sp. seeds, selected for its abundant phytochemical content and potent antioxidant properties. The study characterized the fundamental composition of the husk used as the primary material and through hydrothermal extraction (autohydrolysis), a sustainable approach applying subcritical water conditions, the husk samples were processed for the solubilization of different compounds. Towards understanding the technique's impact, varying solid-to-liquid ratios—1:8 (w:v) and 1:30 (w:v)—were employed, while maintaining a constant temperature of 160 °C. The resulting extracts underwent different analyses via distinct spectrophotometric methodologies. Total phenolic compound content (TPC) is assessed using the Folin-Ciocalteu method, while TEAC, DPPH, and FRAP assays gauge extract antioxidant capacities. The findings emphasized that elevating the solid-to-liquid ratio from 1:8 to 1:30 (w:v) correlates with heightened phenolic compounds and enhanced antioxidant activity.