Phenylpropanoid Glycoside Analogues: Enzymatic Synthesis, Antioxidant Activity and Theoretical Study of Their Free Radical Scavenger Mechanism

Abstract

Phenylpropanoid glycosides (PPGs) are natural compounds present in several medicinal plants that have high antioxidant power and diverse biological activities. Because of their low content in plants (less than 5% w/w), several chemical synthetic routes to produce PPGs have been developed, but their synthesis is a time consuming process and the achieved yields are often low. In this study, an alternative and efficient two-step biosynthetic route to obtain natural PPG analogues is reported for the first time. Two galactosides were initially synthesized from vanillyl alcohol and homovanillyl alcohol by a transgalactosylation reaction catalyzed by Kluyveromyces lactis β-galactosidase in saturated lactose solutions with a 30%–35% yield. To synthesize PPGs, the galactoconjugates were esterified with saturated and unsaturated hydroxycinnamic acid derivatives using Candida antarctica Lipase B (CaL-B) as a biocatalyst with 40%–60% yields. The scavenging ability of the phenolic raw materials, intermediates and PPGs was evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) method. It was found that the biosynthesized PPGs had higher scavenging abilities when compared to ascorbic acid, the reference compound, while their antioxidant activities were found similar to that of natural PPGs. Moreover, density functional theory (DFT) calculations were used to determine that the PPGs antioxidant mechanism proceeds through a sequential proton loss single electron transfer (SPLET). The enzymatic process reported in this study is an efficient and versatile route to obtain PPGs from different phenylpropanoid acids, sugars and phenolic alcohols.

Maclurin protects against hydroxyl radical-induced damages to mesenchymal stem cells: Antioxidant evaluation and mechanistic insight

“…It means that maclurin could effectively scavenge ABTS +Å through e transfer. The e transfer however is always accompanied by deprotonation, so it is usually termed SEPT [41], or equential proton loss single electron transfer (SPLET) [14], proton coupled electron-transfer (PCET) [42]. The SEPT mechanism for maclurin to scavenge ABTS +Å is proposed as described in Fig.…”

“…The antioxidant mechanisms of phytophenol, however, have been reported to include three main types, i.e., hydrogen atom (H Å ) transfer (HAT), sequential electron (e) proton transfer (SEPT), and radical adduct formation (RAF) [12,13]. These antioxidant mechanisms have attracted increasing attention from theoretical scientific communities, and a lot of researchers have recently used density functional theory (DFT) of computational chemistry to calculate the antioxidant mechanisms in various models, such as phenylpropanoid glycoside analogs towards DPPH Å (1,1-diphenyl-2-picrylhydrazyl radical) [14], sinapinic acid towards ROS [15], aurones towards Å O 2 À and DPPH Å [16]. Litwinienko and Ingold used DFT to investigate the solvent effect on HAT mechanism for phenolic antioxidant [17,18].…”

Protective Effect Against Hydroxyl Radical-induced DNA Damage and Antioxidant Mechanism of [6]-gingerol: A Chemical Study

“…28 In the process, e transfer is always accompanied by deprotonation, so it is termed a sequential electron proton transfer (SEPT) mechanism, 29 or proton coupled electron-transfer (PCET) mechanism, 30 sequential proton loss single electron transfer (SPLET). 31 The SEPT mechanism for [6]-gingerol to scavenge ABTS + • was proposed as described in Figure 6. Through SEPT mechanism, [6]-gingerol might change to phenoxyl radical (I).…”

Transgenic peanut overexpressing mtlD gene confers enhanced salinity stress tolerance via mannitol accumulation and differential antioxidative responses

“…Ascorbic acid (AsA) is both a secondary metabolite and an antioxidant which interacts enzymatically and non-enzymatically and detoxifies the ROS (Upadhyaya et al 2011). Therefore, AsA is used as a reference compound in a number of studies associated with stress tolerance in plants (Lopez-Munguia et al 2011). When compared with WT, an increase in the AsA content was recorded in T lines with increasing salinity stress (Fig.…”