A novel ultrasonic-assisted technique for eco-friendly extraction of oligostilbenes from the Paeonia delavayi seed coat and the inhibition on 3 C-like protease

Abstract

The main purpose of this study is to establish an efficient method for extracting oligostilbenes from the Paeonia delavayi Franch seeds coat (PDSC), and explore their inhibition on 3 C-like protease (3CLpro). Ultrasonic-assisted natural deep eutectic solvent (UAE-NADES) method was used to extract oligostilbenes from PDSC, and the extraction process conditions were optimized using response surface methodology (RSM). The inhibition of oligostilbenes on 3CLpro, an enzyme necessary for replication of 2019-nCoV, was tested by fluorescence intensity (FI) method. The optimistic extraction conditions were determined as follows: ultrasonic time 18 min, ultrasonic temperature 35°C, Choline chloride/Sorbitol/Ethylene glycol (CSEG) molar ratio 2:1:4, ultrasonic power 300 W. Under these extraction conditions, the extraction rates of suffruticol A (SA), suffruticol B (SB), suffruticol C (SC), trans-ε-viniferin (TV), trans-gnetin H (TG), and total oligostilbenes compounds (TOC) were 73.66 ± 4.32%, 78.74 ±5.28%, 88.12 ± 5.16%, 91.82 ± 6.62%, 89.12 ± 6.37% and 88.27 ± 5.38%, respectively. The UAE-NADES method had lower extraction temperature and better extraction efficiency for oligostilbenes than those of reflux extraction (RE) and ultrasonic-assisted solvent extraction (UASE). SEM analysis found that PDSC powder extracted by UAE-NADES had the most pores and the highest degree of fragmentation, which could fully promote the dissolution of oligostilbenes. Bioactivity evaluation revealed that compounds suffruticol A (SA), suffruticol B (SB), suffruticol C (SC) inhibited 3 CLpro in a dose-dependent manner, and the inhibitory effect of SB and SC could reach up to 70.89% and 77.43%, respectively, indicating that oligostilbenes had a potential inhibitory effect on 3CLpro. This study laid a foundation for the efficient extraction of oligostilbenes which has the potential application as a potential therapeutic drug for COVID-19 by UAE-NADES.