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Title
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Antimicrobial and phytochemical evaluation of the leaves of **Croton linearis** Jacq.
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Author
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Abstract
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| Leaves of Croton linearis, known as “rosemary”, are widely used in folk medicine in Caribbean countries to treat fever and colds that are associated to infections. The increasing resistance of microorganisms to the available antimicrobial agents has attracted the interest in the search of novel antimicrobial natural products. The aim of this thesis was to evaluate the phytochemical and antimicrobial activities of C. linearis leaves to support its ethnomedicinal uses. Initially, the pharmacognostic parameters of the C. linearis leaves were determined and also the physico-chemical quality of the ethanolic extract was studied. The following quality indexes of the leaves and the ethanolic extract were determined: moisture content, total ash, soluble extractive values, refractive index, relative density, pH, UV/vis and TLC fingerprint. A bioassay-guided fractionation and isolation of compounds from the ethanolic extract were performed using flash chromatography and semi-preparative High-Performance Liquid Chromatography-Diode Array Detection-Mass Spectrometry (HPLC-DAD-MS). Isolated compounds were characterized by MS and 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy. In addition, the chemical composition of the essential oil extracted from fresh leaves was determined by Gas Chromatography-Mass Spectrometry. A total seven compounds were isolated and characterized for the first time in this medicinal plant: the alkaloids laudanidine, laudanosine, reticuline, corydine, glaucine and cularine and the flavonoid isorhamnetin-3-O-(6''-O-p-trans-coumaroyl)-?-glucopyranoside. Furthermore, a total of 82 compounds were identified from essential oil, with guaiol (7.93%) as the main component. Then, the microdilution method with resazurin, as well as direct microscopic counting, were used to determine the in vitro antimicrobial activity against bacteria, fungi and parasites. Moreover, the cytotoxicity on three cell lines was evaluated to calculate the selective index (SI). Total extract, chloroform fraction (Cl-F) and essential oil showed activity against the protozoa Trypanosoma and Leishmania with IC50 values ranging from 1 to 26 ?g/mL. The samples showed cytotoxic effects on human fetal lung fibroblasts (MRC-5), murine fibroblasts L929 and PMM (Peritoneal Murine Macrophages). Reticuline showed a weak activity against L. infantum (IC50=148.0 ± 1.2 ?M), while the flavonoid was active against T. cruzi (IC50=35.6 ± 2.3 ?M). The essential oil showed the best SI of 6 for L. amazonensis amastigotes. Conclusions: This is the first pharmacological study for the leaves of C. linearis. The results show the antiprotozoal potential of the ethanolic extract and the essential oil for the development of new herbal medicines to treat African sleeping sickness, leishmaniasis and Chagas disease. |
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Language
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English
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Publication
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Antwerpen
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Universiteit Antwerpen, Faculteit Farmaceutische, Biomedische en Diergeneeskundige Wetenschappen, Departement Farmaceutische Wetenschappen
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2019
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Volume/pages
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154 p.
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Note
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Escalona Arranz, Julio C. [Supervisor]
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Cos, P. [Supervisor]
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Pieters, L. [Supervisor]
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Full text (publisher's version - intranet only)
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