Hydroxycinnamyl Derived BODIPY as a Lipophilic Fluorescence Probe for Peroxyl Radicals.

Jaroslaw Kusio,Adrian Konopko,Grzegorz Litwinienko,Kaja Sitkowska

doi:10.3390/antiox9010088

Abstract

Herein, we describe the synthesis of a fluorescent probe NB-2 and its use for the detection of peroxyl radicals. This probe is composed of two receptor segments (4-hydroxycinnamyl moieties) sensitive towards peroxyl radicals that are conjugated with a fluorescent reporter, dipyrrometheneboron difluoride (BODIPY), whose emission changes depend on the oxidation state of the receptors. The measurement of the rate of peroxidation of methyl linoleate in a micellar system in the presence of 1.0 µM NB-2 confirmed its ability to trap lipid peroxyl radicals with the rate constant kinh = 1000 M−1·s−1, which is ten-fold smaller than for pentamethylchromanol (an analog of α-tocopherol). The reaction of NB-2 with peroxyl radicals was further studied via fluorescence measurements in methanol, with α,α′-azobisisobutyronitrile (AIBN) used as a source of radicals generated by photolysis or thermolysis, and in the micellar system at pH 7.4, with 2,2′-azobis(2-amidinopropane) (ABAP) used as a thermal source of the radicals. The reaction of NB-2 receptors with peroxyl radicals manifests itself by the strong increase of a fluorescence with a maximum at 612–616 nm, with a 14-fold enhancement of emission in methanol and a 4-fold enhancement in the micelles, as compared to the unoxidized probe. Our preliminary results indicate that NB-2 behaves as a “switch on” fluorescent probe that is suitable for sensing peroxyl radicals in an organic lipid environment and in bi-phasic dispersed lipid systems.

Highlights

There is much evidence of the harmful effects of excess amounts of Reactive Oxygen Species (ROS) resulting in oxidative stress, and in undesired effects for health [1,2,3,4,5,6,7,8]
We did not measure the octanol/water partition coefficient, but we roughly assumed that NB-2 should be similar or even more lipophilic than the fluorescent probe with carboxyl functionality presented in Figure 2d, for which Drummen et al determined logP = 2.49 ± 0.04 at pH 7.4 [23]
The typical first step, we examined the ability of NB-2 to react with peroxyl radicals mediating lipid plot of oxygen consumption of such spontaneous polyunsaturated fatty acids (PUFA) peroxidation is presented in Figure 5 as curve peroxidation in 9, a micellar system

Summary

Introduction

There is much evidence of the harmful effects of excess amounts of Reactive Oxygen Species (ROS) resulting in oxidative stress, and in undesired effects for health [1,2,3,4,5,6,7,8].

Methods

Results

Conclusion