Optimization of Phenolics Extraction from Strobilanthes cusia Leaves and their Antioxidant Activity

Strobilanthes cusia (Nees) Kuntze is commonly used as a traditional medicine with widespread health benefits. This work proposed S. cusia leaves as a potential source of phenolic compounds for extraction and examined the antioxidant capacity of the phenolic-rich extract. Several solvents (ethanol, methanol, and water) were screened as extractants. Among these, methanol showed the highest extraction efficiency. Single-factor experiments and response surface methodology were then applied to optimize the extraction conditions. The maximum total phenolic content of 64.86 ± 0.32 mg GAE/g was obtained under the following extraction conditions: extraction time, 2.27 h; methanol-to-material ratio, 9.55 mL/g; aqueous methanol concentration, 63.54%. The phenolic-rich extract showed potential antioxidant capacity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical at an IC50 value of 464.59 μg/mL. This study shows that S. cusia leaves are rich in phenolic constituents and suggests S. cusia leaf extracts as promising antioxidant agents for future applications.