Separation of antioxidant-rich Alternanthera Sessilis Red extracts by Sephadex LH-20 and identification of polyphenols using HPLC-QToF-MS/MS.

Abstract

This study aimed to fractionate Alternanthera sessilis Red (ASR) crude extracts and determine their antioxidant activities as well as the related active components in the whole plant. ASR was extracted with water and ethanol, and further separated using a Sephadex LH-20 column. Following the assessments of the polyphenolic contents and antioxidant activities of crude extracts (H2OASR and EtOHASR) and fractions, a HPLC-QToF analysis was performed on the crude extracts and selected fractions (H2OASR FII and EtOHASR FII). Three water fractions (H₂OASR FI, FII and FIII) and four ethanolic fractions (EtOHASR FI, FII, FIII and FIV) were derived from their crude extracts, respectively. EtOHASR FII exhibited the greatest total phenolic content (120.41 mg GAE/g fraction), total flavonoid content (223.07 mg RE/g fraction), and antioxidant activities (DPPH IC50 = 159.43 μg/mL; FRAP = 1.93 mmol Fe2+/g fraction; TEAC = 0.90 mmol TE/g fraction). Correlation analysis showed significant (p < 0.01) positive correlations between both TPC (r = 0.748-0.970) and TFC (r = 0.686-0.949) with antioxidant activities in the crude extracts and fractions. Flavonoids were the major compounds in the four selected samples tentatively identified using HPLC-QToF-MS/MS, with the highest number of 30 polyphenol compounds detected in the most active fraction, EtOHASR FII.