Pentaclethra macroloba tannins fractions active against methicillin-resistant staphylococcal and Gram-negative strains showing selective toxicity

Abstract

Abstract:The ethanol extract of the vegetal species Pentaclethra macroloba (Willd.) Kuntze, Fabaceae, was fractioned and the antibacterial activity was determined. The active ethyl acetate (ea) fraction showed activity against Gram-positive (Staphylococcus spp. and Enterococcus spp.) and Gram-negative (Pseudomonas aeruginosa, Acinetobacter spp. and Klebsiella pneumoniae) multiresistant bacteria. Gallic acid derivatives were identified as the main compounds in inactive subfractions from the ea fraction, while the active one afforded ellagic acid as the major constituent when submitted to acid hydrolysis reaction, which suggests the presence of hydrolysable tannins. The minimum bactericidal concentration analysis showed a bactericide mechanism of action for the tannin subfraction found. The antibacterial mechanism of action of the active tannin subfraction against S. aureus reference strains (ATCC 29213 e 33591) was proposed adopting an in vitro assay of protein synthesis inhibition. For this, bacterial cells were labeled with [ 35 S] methionine in the presence of the subfraction. The protein synthesis inhibition was observed at 256 μg/mL of this subfraction. At this concentration it did not present cytotoxicity in eukaryotic cells by the neutral red technique, suggesting selective toxicity. The present study is the first in vitro investigation of the antibacterial properties of tannin fractions obtained from a polar extract of P. macroloba.

Case Series: The Effectiveness of Fatty Acids from Pracaxi Oil in a Topical Silicone Base for Scar and Wound Therapy

“…Pracaxi oil, derived from the seeds of the Pentaclethra macroloba tree indigenous to the Amazon, has several medicinal applications including the treatment of ulcers, stretch marks, bacterial infections, and snake bites [ 9 , 10 ]. Pracaxi oil contains high amounts of oleic, linoleic, and behenic fatty acids, which are frequently utilized in the cosmetic industry [ 9 ] and have been shown to enhance wound closure and improve healing in several wound models [ 11 , 12 ].…”

In vitro potentiation of carbapenems with tannic acid against carbapenemase-producing enterobacteriaceae: exploring natural products as potential carbapenemase inhibitors

“…However, we hypothesize that the initial increase in cell viability might be due to TA serving as nutrients for the cells, but became toxic to the cells at 64–256 mg l −1 by reducing nutrient availability and/or inhibiting metabolic enzymes’ activity in the cell via its astringent action (https://www.britannica.com/science/tannin) (Leal et al . ; Tintino et al . ).…”

In Vitro Potentiation of Carbapenems with Tannic Acid Against Carbapenemase Producing Enterobacteriaceae: Exploring Natural Products as Potential Carbapenemase Inhibitors

“…Available evidence from published studies show that tannins, which includes TA, catechin, ethylgallate, epicatechin gallate, epigallocatechin gallate, methyl gallate, ellagic acid, rosmaric acid and 1,2,3,4,6-Penta-O-galloyl-b-D-glucopyranose are polyphenolics that are abundant in plants (Leal et al 2011; Slobodníková et al 2016) (Fig. S1).…”

“…Tannin extracts and fractions have been reported to either potentiate or modify the effects of β-lactams, fluoroquinolones, and several other antibiotic classes (Leal et al 2011; Myint et al 2013; Slobodníková et al 2016). Moreover, they have been shown to inhibit biofilm formation, quench quorum sensing, and confer antimicrobial and antioxidant activity against bacteria by binding to bacterial proteins, cell wall and cell membrane structures, resulting in cell lysis and efflux pumps inhibition (Leal et al 2011; Myint et al 2013; Slobodníková et al 2016). However, the reported antibacterial and efflux inhibition effects of tannins were not seen in this study, intimating that other tannins besides TA may be responsible for those effects.…”

“…In an earlier study, Leal et al (Leal et al 2011) found that the tannin fractions of Pentaclethra macroloba was bactericidal to bacteria in a dose- dependent manner by inhibiting protein synthesis, although protein binding is the universally accepted mechanism of tannins’ biological and astringent activity (Slobodníková et al 2016). Notably, the tannin fraction was found to be non-toxic to eukaryotic cells at the effective bactericidal concentration (Leal et al 2011). As TA alone was not active against the Enterobacteriaceae isolates used in this study it is obvious that it did not inhibit protein synthesis supporting our hypothesis a potential carbapenemase inhibitor.…”