Optimization of PEG 200 Extraction Process and in Vitro Antioxidant Activity of Polyphenols from Dendrobium nobilis Flower

Objective: To extract polyphenols in Dendrobium nobilis flower (DNF) through a green process method and to evaluate its antioxidant activity in vitro. Methods: Using PEG 200 as solvent, the single factors tests and response surface experiments were conducted to optimize the extraction conditions on the yield of polyphenols from DNF. AB-8 macroporous resin adsorption technology was applied for the enrichment of the above polyphenols and the recycling of PEG 200. The ABTS and DPPH assays were performed to investigate the antioxidant properties of those polyphenols. Results: The optimal parameters were as follows: The solvent volume fraction was 55%, the liquid-solid ratio was 38:1 mL·g⁻¹, the ultrasonic time was 99 min, the ultrasonic temperature was 80 ℃. The polyphenols yield could reached up to 338.88 mg·g⁻¹ in these conditions. Within the test concentration range, the antioxidant capacity in vitro of those polyphenols was similar to that of ascorbic acid. The IC₅₀ of ABTS and IC₅₀ of DPPH free radicals of the polyphenols were 4.486 and 2.792 mg·mL⁻¹ respectively. Conclusion: The green solvent PEG 200 can be used for the extraction of polyphenols from Dendrobium nobilis flower and can be reused; the in vitro antioxidant capacity of the extracted polyphenols is strong, which has good prospects for development and application.