Efficient, green extraction of two biflavonoids from Selaginella uncinata with deep eutectic solvents

• Amentoflavone (AME) and robustaflavone (ROB) were firstly extracted from S. uncinata with eco-friendly DES. • 30 DESs were prepared, novel proline-lactic acid (Pro-Lac) was selected as the optimal DESs. • DES method exhibited higher extraction efficiency than the traditional methods. • 23 flavonoids were identified in S. uncinata by UPLC-Q-TOF-MS, in which 6 compounds were first discovered. • DES extract proved to have promising antioxidant and anticancer activity. • The selected DES has good recyclability and reusability. In this study, ultrasonic-assisted deep eutectic solvents (DESs-UAE) was applied for efficient and environmentally friendly extraction of amentoflavone (AME) and robustaflavone (ROB) from Selaginella uncinata. Firstly, proline-lactic acid (Pro-Lac) was screened as the optimal DES from the 30 DESs. The maximum extraction rates of AME and ROB were obtained adopting the response surface methodology (RSM). Under the optimal conditions of molar ratio of 1:4, water content of 33 %, and extraction time of 30 min, the extraction yields of AME and ROB were 709.72±11.31 μg/g and 145.13±9.77 μg/g, respectively. Compared with the traditional extraction methods, the DESs-UAE extraction could enhance the extraction rates and save extraction time. At the same time, 23 flavonoids were identified by UPLC-Q-TOF-MS, of which 6 components appeared for the first time in S. uncinata. In addition, three antioxidant experiments (DPPH method, ABTS method, and hydroxyl radical scavenging method) were carried out, and the results showed that the S. uncinata extracts had potential antioxidant activity. Furthermore, S. uncinata extracts exhibited obvious growth inhibitory effect on A549, HCT-116, HT-29, sw1990, HepG2 and HeLa cancer cells. In conclusion, deep eutectic solvent, as an promising solvent, is much more effective and simple extraction of bioactive constituents from S. uncinata with high safety and low toxicity.