Ultrasonic-Assisted Aqueous Two-Phase Extraction Combined with Macroporous Resin Enrichment of Lignans from Flaxseed Meal and Their Antioxidant Activities

J AOAC Int. 2021 Oct 8;qsab124. doi: 10.1093/jaoacint/qsab124. Online ahead of print.

Abstract

Background: Secoisolariciresinol di glucoside (SDG) is a natural antioxidant generally extracted from flaxseed, which is one of the most important oil crops in China, the by-product of the flaxseed oil, i.e., flaxseed meal, still contains a lot of lignans. However, flaxseed meal is generally treated as waste, resulting in a huge waste of resources.

Objective: To establish an efficient and convenient method for extraction and purification of lignans from flaxseed meal.

Methods: First, we used response surface methodology (RSM) to optimize the extraction conditions of the ultrasonic-assisted aqueous two-phase system (UAATPS), and we obtained the purified extracts by macroporous resin purification (MRP). Second, the antioxidant ability of the extracts was studied in vitro.

Results: The best extraction conditions obtained were as follows: 9.0 wt% sodium hydroxide, 30.0 wt% isopropanol, extraction time 39 min, liquid-to-solid ratio of 52.0 mL/g, ultrasonic wave 560 W, and extraction temperature 40 °C. Under the optimal conditions, the purity of crude extracts (SDG-APTS-C) reached 21.5%. The desorption conditions of MRP were as follows: eluting 3 BV with ultrapure water, and then eluting with 25% ethanol at 2 BV/h to collect eluents. The purified extracts (SDG-ATPS-P) had a purity quotient of 73.9%, 52.4% higher than that of SDG-ATPS-C. Additionally, experiments conducted in this paper revealed that SDG-ATPS-C and SDG-ATPS-P could effectively remove DPPH, ABTS, and hydroxyl free radicals in vitro.

Conclusions: The method was validated for extracting SDG from flaxseed meal, thus achieving the reuse of flaxseed meal.

Highlights: This research provides some references for the application of UAATPS combined with MRP in natural products.