Chilean Rhubarb, Gunnera tinctoria (Molina) Mirb. (Gunneraceae): UHPLC-ESI-Orbitrap-MS Profiling of Aqueous Extract and its Anti-Helicobacter pylori Activity.

Sonja Hebel-Gerber,Javier Echeverría,Julio Alarcón,Angélica Urbina,Edgar Pastene-Navarrete,Apolinaria García-Cancino,Luis Bustamante-Salazar,Katia Sáez-Carrillo,Mario J Simirgiotis

doi:10.3389/fphar.2020.583961

Abstract

The full UHPLC-MS metabolome fingerprinting and anti-Helicobacter pylori effect of Gunnera tinctoria (Molina) Mirb. (Nalca) total extract (GTE) and fractions prepared from its edible fresh petioles were evaluated. The activity of G. tinctoria against H. pylori strains ATCC 45504 and J99 was assessed in vitro by means of agar diffusion assay, Minimum Inhibition Concentration (MIC), and Minimum Bactericidal Concentration (MBC), while killing curve and transmission electronic microscopy (TEM) were conducted in order to determine the effect of the plant extract on bacterial growth and ultrastructure. Additionally, the inhibitory effect upon urease was evaluated using both the Jack Bean and H. pylori enzymes. To determine which molecules could be responsible for the antibacterial effects, tentative identification was done by ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-Q-Orbitrap®-HR-MS). Furthermore, the total G. tinctoria extract was fractionated using centrifugal partition chromatography (CPC), giving four active fractions (1–4). It was determined that the crude extract and centrifugal partition chromatography fractions of G. tinctoria have a bactericidal effect being the lowest MIC and MBC = 32 μg/ml. In the killing curves, fraction one acts faster than control amoxicillin. In the urease assay, F3 exhibited the lowest IC50 value of 13.5 μg/ml. Transmission electronic microscopy showed that crude G. tinctoria extract promotes disruption and separation of the cellular wall and outer membrane detachment on H. pylori causing bacterial cell death.

Highlights

Gunnera tinctoria (Molina) Mirb. (Gunneraceae, Figure 1) is a medicinal and edible plant known as Pangue, Nalca (Mapuche voices), or Giant Chilean Rhubarb
A recent paper (Zamorano et al, 2017) reported some antioxidant effects and phenolic compounds of G. tinctoria; no mass spectrometry analysis was reported to give an accurate idea of the phenolic constituents in the plant
Petiole G. tinctoria extracts exhibited a significant effect against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli with a Minimum Inhibition Concentration (MIC) value of 4.7 mg/ml

Summary

Introduction

Gunnera tinctoria (Molina) Mirb. (Gunneraceae, Figure 1) is a medicinal and edible plant known as Pangue, Nalca (Mapuche voices), or Giant Chilean Rhubarb. H. pylori is a microaerophilic Gramnegative bacterium with a great ability to colonize human gastric mucosa It has a 50% prevalence worldwide (Go, 2002; Malfertheiner et al, 2012) and 73% prevalence in Chile (Ferreccio et al, 2007). A recent paper (Zamorano et al, 2017) reported some antioxidant effects and phenolic compounds of G. tinctoria; no mass spectrometry analysis was reported to give an accurate idea of the phenolic constituents in the plant. Another recent investigation reported in vitro antimicrobial effects of G. tinctoria extracts prepared from flowers, roots, and petiole botanical parts (Velásquez et al, 2020). We reported for the first time the complete metabolome profile using high-resolution Q-Orbitrap technology coupled to a PDA detector (UHPLC-PDA-Q-Orbitrap-HR-MS), and we demonstrate that G. tinctoria aqueous extract and their fractions obtained by CPC have in vitro lethal effect against the important pathogen H. pylori

Methods

Results

Conclusion