Chemical fingerprinting and bioactivity of Amazonian Ecuador Croton lechleri Mull. Arg. (Euphorbiaceae) stem bark essential oil: A new functional food ingredient?

Croton lechleri essential oil has been obtained by steam distillation of fresh stem bark from Amazonian Ecuador adult plants (yield: 0.61 ml/kg [0.061%]; density: 1.01 g/ml), and then chemically characterised by GC (Gas Chromatography) and GC-MS (gas chromatography-mass spectrometry). Seventy-four chemicals were detected and identified: the most abundant in descending order, were the sesquiterpenes sesquicineole (17.29%), alpha-calacorene (11.29%), 1,10-di-epi-cubenol (4.75%), beta-calacorene (4.34%) and epicedrol (4.09%). Monoterpenes checked with a relative peak area higher than 2.0% were alpha-pinene (2.01%), p-cymene (2.61%), limonene (4.20%) and borneol (2.67%). The structure of the main chemicals were confirmed by GC-MS and H-1 NMR analyses. Spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and DPPH-( high performance) thin layer chromatography (DPPH-(HP)TLC) bioautographic assays showed a lower radical scavenging capacity (IC50) with respect to commercial thyme essential oil and BHA (butylated hydroxyl anisole), pointing out, however, that the C lechleri essential oil fraction. characterised by alpha-calacorene, beta-calacorene and delta-cadalene, was the most involved in the bioactivity. Similar results were obtained with beta-carotene bleaching assay, where the IC50 values were 0.291 +/- 0.024 mg/ml for C. lechleri essential oil, 0.164 +/- 0.013 and 1.34 x 10(-4) +/- 10(-5) mg/ml for thyme essential oil and BHA, respectively. (HP)TLC-bioautographic assay performed with Gram positive and Gram negative bacteria revealed a minimum inhibitory concentration (MIC) values comprised between 0.10 mg/ml (Escherichia coli) and 10.10 mg/ml (for e.g. Pseudomonas aeruginosa), and the fraction mainly characterised by sesquicineole (97.38%) as the most involved in antibacterial capacity. Ames test employing Salmonella typhimurium TA98 and TA100 with and without a metabolic activation mixture (S9 mix) demonstrated the absence of mutagenicity of the C. lechleri essential oil between a concentration range of 10(-2) and 100 mg/plate. The same results were achieved by Saccharomyces cerevisiae D7 strain assay. An interesting mutagen-protective efficacy was evidenced by a 30% and 33% revertants reduction of TA98 strain treated with 2-aminoanthracene and nitrofluorene (2 mu g/plate), suggesting, above all, the possibility to employ C. lechleri essential oil as a new flavouring protective ingredient for foods or dietary supplements against potential mutagens formed during cooking and/or processing in general. (C) 2010 Elsevier Ltd. All rights reserved.