Protective effect of Pterostilbene against free radical mediated oxidative damage

Abstract

Background: Pterostilbene, a methoxylated analog of Resveratrol, is gradually gaining more importance as a therapeutic drug owing to its higher lipophilicity, bioavailability and biological activity than Resveratrol. This study was undertaken to characterize its ability to scavenge free radicals such as superoxide, hydroxyl and hydrogen peroxide and to protect bio-molecules within a cell against oxidative insult.

Methods: Anti-oxidant activity of Pterostilbene was evaluated extensively by employing several in vitro radical scavenging/inhibiting assays and pulse radiolysis study. In addition, its ability to protect rat liver mitochondria against tertiary-butyl hydroperoxide (TBHP) and hydroxyl radical generated oxidative damage was determined by measuring the damage markers such as protein carbonyls, protein sulphydryls, lipid hydroperoxides, lipid peroxides and 8-hydroxy-2'-deoxyguanosine. Pterostilbene was also evaluated for its ability to inhibit •OH radical induced single strand breaks in pBR322 DNA.

Result: Pterostilbene exhibited strong anti-oxidant activity against various free radicals such as DPPH, ABTS, hydroxyl, superoxide and hydrogen peroxide in a concentration dependent manner. Pterostilbene conferred protection to proteins, lipids and DNA in isolated mitochondrial fractions against TBHP and hydroxyl radical induced oxidative damage. It also protected pBR322 DNA against oxidative assault.

Conclusions: Thus, present study provides an evidence for the strong anti-oxidant property of Pterostilbene, methoxylated analog of Resveratrol, thereby potentiating its role as an anti-oxidant.

Figure 1

Radical scavenging/inhibition by Pterostilbene. (A) DPPH, (B) FRAP Assay, (C) ABTS, (D) Hydroxyl radical, (E) Superoxide radical and (F) H₂O₂ assay.

Figure 2

Radical scavenging assays by pulse radiolysis. Decay curve for ABTS^.+ radical (A) and CO₃•^– radical (B) in presence of different concentrations of (i) Ascorbic acid (1: Control, 2–5: 0.1, 0.2, 0.3 and 0.4 mM) and (ii) Pterostilbene. (1: Control, 2–5: 0.05, 0.1, 0.15 and 0.20 mM). Hydroxyl radical scavenging activity (C) by competitive kinetics in presence of different concentrations of (i) Ascorbic acid (1: Control, 2–5: 0.1, 0.2, 0.3 and 0.4 mM) and (ii) Pterostilbene. (1: Control, 2–5: 0.05, 0.1, 0.15 and 0.20 mM).

Figure 3

A. Gel electrophoresis pattern of pBR322 plasmid DNA after induction of oxidative damage in the presence of different concentrations of Pterostilbene. Lane 1-Undamaged DNA; Lane 2- Damaged DNA in presence of hydroxyl radical; Lane 3-DNA in presence of Pterostilbene alone; Lanes 4-7- oxidatively damaged DNA in presence of 0.05, 0.10, 0.15 and 0.20 mM Pterostilbene, respectively. B. Densitogram analysis of electrophoreogram to quantitate supercoiled and nicked circular DNA. Values are expressed as mean ± SE. Dissimilar alphabets in superscript indicate significant difference at p< 0.05.