Question

Bioassay-guided isolation and antioxidant evaluation of flavonoid compound from aerial parts of lippia nodiflora l.

Answer 1

The present study was designed to identify the DPPH (2, 2-diphenyl-1-picrylhydrazyl) free-radical scavenging constituents from methanol extract of L. nodiflora using bioassay-guided fractionation. The ethyl acetate fraction (EAF) revealed a strong antioxidant activity, compared to other fractions through in vitro DPPH radical-scavenging assay. The repeated fractionation of active EAF by silica gel column chromatography yielded a compound with strong antioxidant potential. The isolated bioactive compound was determined as 2-(3, 4-dimethoxyphenyl)-5-hydroxy-7-methoxy-4H-chromen-4-one (5-hydroxy-3′, 4′, 7-trimethoxyflavone), by comparing spectral data (UV, IR, 1H NMR, 13C NMR, and MS) with literature reports. The isolated compound demonstrated an excellent antioxidant activity through all antioxidant assays and also significantly inhibited lipid peroxidation at a concentration of 50 μg/mL. The results obtained suggested that extracts from L. nodiflora or its derived phytocompound can be used potentially as a bioactive source of natural antioxidants by contributing beneficial health effects.

1. Introduction

Reactive oxygen species (ROS) are continuously formed as a by-product of metabolisms in aerobic organisms and are also produced on exposure to tobacco smoke, ozone, radiations, organic solvents, and other environmental pollutants [1]. ROS play an important role in various physiological processes, including energy production, phagocytosis, cellular signal transduction, cell proliferation, differentiation, and apoptosis. On the other hand, increasing evidence highlights that overproduction of ROS can induce oxidative damage to all biomolecules (lipids, carbohydrates, proteins, enzymes, DNA, and RNA) and acts as a mediator of numerous disorders, for example, inflammation, arthritis, diabetes, arteriosclerosis, cancer, genotoxicity, and neurological disorders such as Alzheimer’s disease [2]. Antioxidants are very essential for averting degenerative reactions produced by free radicals and reactive oxygen species, which have been concerned with many diseases and in food deterioration and spoilage [3]. However, the safety of some of the synthetic antioxidants used in the food industry has been questioned, because recent studies recognized that they might be carcinogenic [4]. Hence, there is an emerging interest in natural antioxidants, which might help to prevent oxidative damage [5].

Plants and plant products are magnificent sources of phytochemicals and have been found to hold an array of biological activities including antioxidant potential [6]. Plants synthesize antioxidant compounds, mostly flavonoids and polyphenols, which have been reported to protect the human body from various diseases by neutralizing ROS. Recently, phenolic compounds have received increasing significance among various phytochemicals, due to their wide distribution in the plant kingdom and for their biological activities, namely, anticarcinogenic, antiatherogenic, anti-inflammatory, antimicrobial, and antioxidant activities [7–9]. Antioxidants can be either used as dietary, food supplement or as a drug by the humans [10]. Several studies have revealed that the increased dietary intake of natural antioxidants, such as flavonoids and other phenolic compounds, almost present in plants, exhibits potential protective effects against many degenerative diseases [