L-Rhamnose and Phenolic Esters-Based Monocatenar and Bolaform Amphiphiles: Eco-Compatible Synthesis and Determination of Their Antioxidant, Eliciting and Cytotoxic Properties

Abstract

Symmetrical and dissymmetrical bolaforms were prepared with good to high yields from unsaturated L-rhamnosides and phenolic esters (ferulic, phloretic, coumaric, sinapic and caffeic) using two eco-compatible synthetic strategies involving glycosylation, enzymatic synthesis and cross-metathesis under microwave activation. The plant-eliciting activity of these new compounds was investigated in Arabidopsis model plants. We found that the monocatenar rhamnosides and bolaforms activate the plant immune system with a response depending on the carbon chain length and the nature of the hydrophilic heads. Their respective antioxidant activities were also evaluated, as well as their cytotoxic properties on dermal cells for cosmetic uses. We showed that phenolic ester-based compounds present good antioxidant activities and that their cytotoxicity is low. These properties are also dependent on the carbon chains used.

Keywords: amphiphilic; antioxidant; bolaform; dermal cytotoxicity; microwaves; monocatenar; phenolic acids; plant immunity; rhamnosides.

Figure 1

Examples of surfactants.

Figure 2

Structures of derivatives of hydroxycinnamic acids.

Scheme 1

Glycosylation of L-rhamnose.

Scheme 2

Metathesis of L-rhamnoside.

Scheme 3

Cross-metathesis between rhamnosides and phenolic esters.

Scheme 4

Reaction of an antioxidant with the DPPH● radical.

Figure 3

Plant-eliciting activities of monocatenar rhamnosides. Extracellular reactive oxygen species (ROS) production following treatment of Arabidopsis with C6 to C11 rhamnosides. Production of ROS was measured in leaf disks following treatment with the synthetic glycolipids at 100 µM. MeOH (0.5%) was used as a control. ROS production was measured using the chemiluminescence of luminol, and photon counts were expressed as relative luminescence units (RLUs). Histograms were calculated as the total RLUs over 12 h of monitoring. Data are mean (n = 6). Experiments were independently realized twice with similar results.

Figure 4

Plant-eliciting activities comparison between saturated and unsaturated monocatenar rhamnosides. Production of ROS was measured in leaf disks following treatment with the synthetic glycolipids at 100 µM. MeOH (0.5%) was used as a control. ROS production was measured using the chemiluminescence of luminol, and photon counts were expressed as relative luminescence units (RLUs). Histograms were calculated as the total RLUs over 12 h of monitoring. Data are mean ± SEM (n = 6). Experiments were independently realized twice with similar results.

Figure 5

Plant-eliciting activities comparison between C11 rhamnoside, C20 dissymmetrical and symmetrical bolaforms. Production of ROS was measured in leaf disks following treatment with the synthetic glycolipids at 100 µM. MeOH (0.5%) was used as a control. ROS production was measured using the chemiluminescence of luminol and photon counts were expressed as relative luminescence units (RLUs). Kinetics of production (left panel) and sum of RLU from the same samples (right panel) are shown. Data are mean ± SEM (n = 6). Experiments were independently realized twice with similar results.

Figure 6

Cytotoxicity of monocatenar unsaturated rhamnosides.

Figure 7

Cytotoxicity of (a) unsaturated bolaform rhamnosides and (b) monocatenar and bolaform rhamnosides.

Figure 8

Cytotoxicity of (a) unsaturated monocatenar phloretic esters and (b) dissymmetric bolaforms.