Mirta S. Demo

Antimicrobial Activity of Essential Oils Obtained from Aromatic Plants of Argentina

ABSTRACT The aim of this work was to evaluate the antibacterial and antifungal activity of essential oils obtained from medicinal plants of the Argentine Republic. The antimicrobial activity of the essential oils of 14 plants collected from different zones was analyzed. The microorganisms used were Staphylococcus aureus., Staphylococcus epidermidis., Bacillus cereus., Micrococcus luteus., Enterococcus faecalis., Escherichia coli., Klebsiella. sp., Proteus mirabilis., Pseudomonas aeruginosa., and the yeast Candida albicans.. The disk diffusion method was performed to test antimicrobial activity. B. cereus. and S. aureus. were inhibited by most of the essential oils. Aloysia triphylla., Psila spartoides., and Anemia tomentosa. were the most effective compounds against B. cereus., while A. triphylla. and Baccharis flabellata. were effective against S. aureus.. None of the oils inhibited P. aeruginosa.. B. flabellata. and Pectis odorata. were active only against Gram-positive bacteria. A. triphylla. and P. spartoides. inhibited all tested microorganism, and the remaining essential oils showed variable activity. The minimum inhibitory concentration (MIC) of A. triphylla. and P. spartoides. essential oils were determined using the disk diffusion method. The lowest MICs were against S. aureus. (1/16), B. cereus. (1/16), S. epidermidis. (1/8), and C. albicans. (1/32) for A. triphylla.. The lowest MICs were against S. aureus. (1/32), B. cereus. (1/32), P. mirabilis. (1/32), and C. albicans. (1/64) with P. spartoides.. The results showed that B. cereus. and S. aureus. were the most sensitive microorganisms, and P. aeruginosa. was the most resistant microorganism. This study may contribute to improve ethnobotanical knowledge and would help to discover substances with potential therapeutical uses, as food preservants or as food-borne pathogen inhibitors.

In vitro activity of natural phenolic compounds against fluconazole-resistant Candida species: a quantitative structure–activity relationship analysis

To evaluate the antifungal activity and to analyse the structure–activity relationship of eleven natural phenolic compounds against four Candida species which are resistant to fluconazole.

Antimicrobial Activity and Composition of Hyptis mutabilis Essential Oil

ABSTRACT An analysis of the hydrodistilled essential oil from fresh aerial parts of Hyptis mutabilis (Rich) Briq. by GC/MS resulted in the identification of 24 compounds that represented 95.5 percent of the oil. The main constituents of the oil were E-caryophyllene (14.7%), spathulenol (14.2%) and germacrene D (11.1%). The oil exhibited significant antimicrobial activity against Mucor sp.

Structure and Antimicrobial Activity of Phloroglucinol Derivatives from Achyrocline satureioides

The new prenylated phloroglucinol α-pyrones 1-3 and the new dibenzofuran 4, together with the known 23-methyl-6-O-demethylauricepyrone (5), achyrofuran (6), and 5,7-dihydroxy-3,8-dimethoxyflavone (gnaphaliin A), were isolated from the aerial parts of Achyrocline satureioides. Their structures were determined by 1D and 2D NMR spectroscopic studies, while the absolute configuration of the sole stereogenic center of 1 was established by vibrational circular dichroism measurements in comparison to density functional theory calculated data. The same (S) absolute configuration of the α-methylbutyryl chain attached to the phloroglucinol nucleus was assumed for compounds 2-6 based on biogenetic considerations. Derivatives 7-16 were prepared from 1 and 5, and the antimicrobial activities of the isolated metabolites and some of the semisynthetic derivatives against a selected panel of Gram-positive and Gram-negative bacteria, as well as a set of yeast molds, were determined.

Variation in the Essential Oil Composition and Antimicrobial Activity of Baccharis spartioides (H. et A.) J. Rimy from Three Regions of Argentina.

Abstract Hydrodistilled oils of Baccharis spartioides from three populations of Argentina (Northwest, Central and Patagonia areas) were analyzed by using GC and GC/MS. Thirty-nine compounds were identified in the oils and a relatively high variation in their contents and in their antimicrobial activity was found. The main constituents of the oils were camphor (26.5–50%), limonene (4.3–35.8%), citronellal (12%), carvone (10%) and spathulenol (2.1–11.8%). The oil was tested against ten Gram-positive and Gram-negative bacteria and against the yeast Candida albicans. The best antimicrobial activity of the oils of B. spartioides was against S. aureus and B. cereus while P. aeruginosa was the most resistant bacteria to all the oils.

Inhibition of immediate-type allergic reaction by Minthostachys verticillata (Griseb.) Epling essential oil

Abstract An oil of Minthostachys verticillata (Griseb.) Epling was analyzed by GC. The main constituents identified were pulegone (63.0%) and menthone (16.4%). It was found that the oil inhibited β-hexosaminidase release from basophils. Forty-two percent of the cells present in lymphocyte cultures stimulated by the oil were CD8(+) T cells and showed higher IFN-γ levels than non-stimulated cultures (p < 0.05). According to these results, the oil was considered to be a Th1 deviation inducer, inhibiting the immediate-type allergic reaction.

Natural Products as Alternative Treatments for Candida Species Resistant to Conventional Chemotherapeutics

Abstract The genus Candida comprises more than 200 species, but few of them have been associated with human infections. C. albicans is the most important cause of disease. Other species such as C. dubliniensis , C. glabrata , C. guilliermondii , C. krusei , C. parapsilosis , and C. tropicalis are also being increasingly recognized as significant human pathogens. In recent years, the number of clinical infections caused by Candida species worldwide has risen considerably, and the incidence of resistance to traditional antifungal therapies is also increasing. There is an exigent need for novel antifungal remedies, and plants remain a vital source of these new substances, especially in low-resource countries. Natural compounds are potential antimycotic agents either in their nascent form or as template structures for more effective derivatives. The data and studies described in this chapter document the antimicrobial activity of plant extracts and essential oils against Candida species and show that medicinal plants can be a rich source of potential antifungal compounds.

Essential oil of Rynchosia minima DC. from Kenya : Composition and antibacterial properties

Abstract The hydrodistilled essential oil (yield, 0.1%) of semi-dried leaves of Rynchosia minima DC. was analyzed by GC and GC/MS. Twenty-four compounds representing 95.9% of the oil were identified. The major components were found to be β-caryophyllene (30.4%), germacrene B (17.9%), camphor (7.8%), α-humulene (7.4%) and γ-muurolene (7.3%). The oil was found to exhibit antibacterial activity against Bacillus cerus, Staphylococcus aureus and Micrococcus luteus.

Antimicrobial Natural Products Against Bacterial Biofilms

Bacterial resistance to antibiotics has become the major problem that scientists have to deal with. Pathogenic microorganisms responsible for human, animal, and plant diseases are acquiring resistance due to the inadequate use of antimicrobial drugs. Biofilms are communities of microorganisms adhered to a solid surface and encased in an exopolysaccharide matrix. These cells acquire a number of advantages, such as an increased resistance to antimicrobial agents that makes it difficult to eliminate them. There is an urgent need to discover new antimicrobial substances unable to generate resistance in microorganisms. Plants constitute natural sources of compounds and essential oils; terpenes and extracts obtained from them have been documented to exert antibiofilm and antiquorum sensing activity. The obtaining and identification of plant-derived products are important steps in the development of new active compounds. The extraction of bioactive compounds can be made using different protocols depending on the chemical characteristics of the bioactive compounds of interest. Bioactive plant-derived products would be an interesting natural therapeutic alternative capable of eliminating biofilm without encouraging resistance.