Antioxidant Activities of Extract and Fractions from Receptaculum Nelumbinis and Related Flavonol Glycosides

Abstract

The antioxidant activities of ethanolic crude extract (ECE) and its four different solvent sub-fractions (namely, petroleum ether fraction (PEF), ethyl acetate fraction (EAF), <em>n</em>-butanol fraction (BF) and the aqueous fraction (AF) from the receptacles of <em>Nelumbo </em><em>nucifera</em> Gaertn. (Receptaculum Nelumbinis) were investigated using two <em>in vitro</em> antioxidant assays. BF showed the highest total phenolic content (607.6 mg/g gallic acid equivalents), total flavonoid content (862.7 mg/g rutin equivalents) and total proanthocyanidin content (331.0 mg/g catechin equivalents), accompanied with the highest antioxidant activity compared to other fractions through 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays. Five flavonol glycosides, namely hyperoside (<strong>1</strong>), isoquercitrin (<strong>2</strong>), quercetin-3-<em>O</em>-β-D-glucuronide (<strong>3</strong>), isorhamnetin-3-<em>O</em>-β-D-galactoside (<strong>4</strong>) and syringetin-3-<em>O</em>-β-D-glucoside (<strong>5</strong>) were isolated from the Receptaculum Nelumbinis. Compounds <strong>2</strong>–<strong>5</strong> were isolated for the first time from the Receptaculum Nelumbinis. The five isolated flavone glycosides, particularly compounds <strong>1</strong>–<strong>3</strong>, demonstrated significant DPPH and ABTS radical scavenging activity, with IC₅₀ values of 8.9 ± 0.2, 5.2 ± 0.2, 7.5 ± 0.1 for DPPH and 114.2 ± 1.7, 112.8 ± 0.8, 172.5 ± 0.7 µg/mL for ABTS, respectively. These results suggest that Receptaculum Nelumbinis has strong antioxidant potential and may be potentially used as a safe and inexpensive bioactive source of natural antioxidants.

Keywords

• &lt;em&gt;Nelumbo nucifera&lt;/em&gt; Gaertn.
• receptacle
• DPPH
• ABTS