Inhibitory effect of linalool-rich essential oil from Lippia alba on the peptidase and keratinase activities of dermatophytes

A new flavone and a newly synthesized alkaloid from Lippia rugosa A. Chev (Verbenaceae)

The chemical investigation of the leaf extract of a Cameroonian medicinal plant, Lippia rugosa A Chev (Verbenaceae) led to the isolation of a new flavonoid derivative flavolippia (1), alongside eleven known compounds: 2,4-dimethylpyridin-3,5-diol (2), 5-hydroxy-6,7,4'-trimethoxylflavone (3), 5-hydroxy-3,7,4'-trimethoxyflavone (4), 7-hydroxy-5,6,4'-trimethoxyflavone (5), 3β-hydroxy-urs-12-en-3-ol (α-amyrin) (6), lupeol acetate (7), lup-20(29)-en-3β-ol (lupeol) (8), lup-20(29)-en-3β,28-diol (betulin) (9), fridelan-3-one (fridelan) (10), saccharose (11), cosanol (12). In addition, a new semi-synthetic alkaloid derivative named lippiamicin (13) was prepared from 2,4-dimethylpyridin-3,5-diol (2). Their structures were established on the basis of their spectroscopic data, as well as 1 D and 2 D NMR. Compounds 1-13 were evaluated for their antioxidant activities. The results obtained showed that compounds 2 and 12 were the most active with IC₅₀ values of 0.145 ± 0.011 and 0.195 ± 0.017 µM/mL respectively (for DPPH•) and 0.241 ± 0.027 and 0.223 ± 0.024 µM/mL respectively (for FRAP) compared to butylated hydroxyltoluene used as positive control.

Investigating the Effects of Aqueous and Alcoholic Extracts of Allium Hirtifolium and Allium Jesdianum on Keratinase Activity of Trichophyton Mentagrophytes

Background:

Trichophyton spp., as pathogenic species to humans and animals, cause different forms of dermatophytosis through the production of particular enzymes, playing an essential role in tissue invasion. Among these, herein, keratinase was investigated, for the specific case of Trichophyton mentagrophytes, as a target of the effects of Allium hirtifolium and Allium jesdianum extracts, thus pharmacological potential of these plants was studied against keratinase activity.

Methodology:

Sampling was carried out on 20 bald patients from medical diagnostic laboratories and mycology centers, with suspected dermatophytosis of scalp. For confirming the presence of Trichophyton mentagrophytes in the specimens, different laboratory procedures were applied. Trichophyton mentagrophytes isolates were cultured on a screening medium containing keratin to verify production of the keratinase enzyme. The best enzyme-producing isolate was selected by measuring diameter of transparent halo around colony to be used in subsequent stages. Afterwards, the optimized conditions maximizing enzyme production and activity were determined. Finally, the inhibitory effect of different dilutions of aqueous and alcoholic extracts of Allium jesdianum and Allium hirtifolium on extracellular keratinase activity was studied.

Results :

Sixteen out of 20 fungal isolates were identified as the Trichophyton mentagrophytes. The most desirable reduction on keratinase activity was reported for dilution values of 50 and 100 mg/ml of both aqueous and ethanolic extracts of A.jesdianum, though much more significant decrease belonged to the latter, and for dilution values of 25 and 100 mg/ ml of both aqueous and ethanolic extracts of A.hirtifolium.

Conclusion :

Concerning our results, it is suggested that paying special attention to these natural compounds for the treatment of dermatophytosis could be remarkably effective, considering significant production of keratinase observed in T. mentagrophytes, and they are beneficial, as they have no side effects and offer an alternative to currently available medications, which are under the restriction of drug resistance.

Do essential oils from plants occurring in the Brazilian Caatinga biome present antifungal potential against dermatophytoses? A systematic review

The Caatinga is an exclusively Brazilian biome where semiarid climatic conditions promote singularities in adaptive biodiversity. Many aromatic species are found in this region possessing antifungal properties, which are attributed to their essential oils. Thus, we questioned whether essential plant oils found in the Caatinga present anti-dermatophytic potential. Dermatophytes are keratinophilic fungi that cause one of the most prevalent mycoses globally, skin infections known as dermatophytoses (tineas). Here, we provide a comprehensive report of the available published information, analyzing the methods used to evaluate the antifungal activity, verifying the quality of the evidence and possible clinical applications, and discussing research trends in this area. The plants studied concentrated in the genera Croton (Euphorbiaceae), Lippia (Verbenaceae), Piper (Piperaceae), and Mentha (Lamiaceae). All of the studies used in vitro tests to analyze antifungal potential, and little evidence was ascertained concerning the mechanism of antifungal action. In addition, the essential oils also evidenced drug modifying activity of conventional antifungal drugs (Ketoconazole and Terbinafine). We believe that the anti-dermatophyte potential of plant essential oils occurring within the Caatinga is underestimated and that this review will encourage future chemical-pharmacological investigations into the plants within this biome.Key points• The essential oils from plants occurring in the Caatinga Biome present unknown anti-dermatophyte potential.• The studies against dermatophyte fungi concentrate on the families Lamiaceae and Verbenaceae.• In vitro assays were used to assess the anti-dermatophyte potential of the essential oils.

Essential oils and their components in combating fungal pathogens of animal and human skin

OBJECTIVE

The most common problems of modern medicine include fungal infections of the skin and its appendages caused by dermatomycetes, yeast-like fungi and moulds. Due to toxicity of pharmacological fungicides and promotion of ecology, natural substances with high antifungal properties are sought. Essential oils and their components show potential in this regard.

MATERIAL AND METHOD

Fourteen commercial essential oils were tested for antifungal activity. The study were carried out by agar dilution method against the following fungal species: Microsporum gypseum, Microsporum canis, Trichophyton mentagrophytes, Trichophyton violaceum, Aspergillus niger, Scopulariopsis brevicaulis and (IZ 1) dog skin isolate. The minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) values were determined for all tested oils and individual components of oils with the highest activity against the tested fungi. GC-MS analysis was performed for the most active oils.

RESULTS

Cinnamon, thyme, clove, geranium and manuka oils were most active against the test fungi. The MIC values in the tested oils were in the range of 0.5->10μg/μl and the MFC amounted to 1.25->10μg/μl. Activity of individual components against the tested fungi strains was selective and clearly higher against dermatomycetes fungi and IZ 1 isolate. The strongest effect on dermatomycetes fungi was of cinnamaldehyde, thymol and carvacrol-with the values of 0.039-1.25μg/μl (MIC) and 0.078-1.25μg/μl (MFC). In turn, the highest activity against IZ 1 isolate was of cinnamaldehyde, eugenol, carvacrol, geraniol and thymol. Their MIC and MFC was 0.313-1.25μg/μl.

CONCLUSION

The results prove the applicability of selected oils and their components as alternatives to synthetic agents in combating fungal dermatoses in animals and humans.

Piper Essential Oils Inhibit Rhizopus oryzae Growth, Biofilm Formation, and Rhizopuspepsin Activity

Piper is the largest genus of the Piperaceae family. The species of this genus have diverse biological activities and are used in pharmacopeia throughout the world. They are also used in folk medicine for treatment of many diseases in several countries including Brazil, China, India, Jamaica, and Mexico. In Brazil, Piper species are distributed throughout the national territory, making this genus a good candidate for biological activity screening. During our studies with Piper essential oils, we evaluated its activity against Rhizopus oryzae, the main agent of mucormycosis. The main compounds of seven Piper essential oils analyzed were Piper callosum—safrole (53.8%), P. aduncum—dillapiole (76.0%), P. hispidinervum—safrole (91.4%), P. marginatum—propiopiperone (13.2%), P. hispidum—γ-terpinene (30.9%), P. tuberculatum—(E)-caryophyllene (30.1%), and Piper sp.—linalool (14.6%). The minimum inhibitory concentration of Piper essential oils against R. oryzae ranged from 78.12 to >1250 μg/mL. The best result of total inhibition of biofilm formation was obtained with Piper sp. starting from 4.88 μg/mL. Considering the bioactive potential of EOs against planktonic cells and biofilm formation of R. oryzae could be of great interest for development of antimicrobials for therapeutic use in treatment of fungal infection.

Antimicrobial Activity and Chemical Composition of Essential Oils from Verbenaceae Species Growing in South America

The Verbenaceae family includes 2600 species grouped into 100 genera with a pantropical distribution. Many of them are important elements of the floras of warm-temperature and tropical regions of America. This family is known in folk medicine, and its species are used as digestive, carminative, antipyretic, antitussive, antiseptic, and healing agents. This review aims to collect information about the essential oils from the most reported species of the Verbenaceae family growing in South America, focusing on their chemical composition, antimicrobial activity, and synergism with commercial antimicrobials. The information gathered comprises the last twenty years of research within the South American region and is summarized taking into consideration the most representative species in terms of their essential oils. These species belong to Aloysia, Lantana, Lippia, Phyla, and Stachytarpheta genera, and the main essential oils they contain are monoterpenes and sesquiterpenes, such as β-caryophyllene, thymol, citral, 1,8-cineole, carvone, and limonene. These compounds have been found to possess antimicrobial activities. The synergism of these essential oils with antibiotics is being studied by several research groups. It constitutes a resource of interest for the potential use of combinations of essential oils and antibiotics in infection treatments.

Lippia alba essential oil promotes survival of silver catfish (Rhamdia quelen) infected with Aeromonas sp

In vitro and in vivo activity of the Lippia alba essential oil (EO) against Aeromonas sp. was evaluated. In the in vitro assay the minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of EO for Aeromonas cells were determined using the microdilution method. Twenty five strains of Aeromonas sp. isolated from infected fish obtained from local fish farms were used. MIC and MBC values were 2862 and 5998 µg mL-1 for L. alba EO and 0.5 and 1.2 µg mL-1 for gentamicin, respectively. In the in vivo assay silver catfish juveniles (Rhamdia quelen) (7.50 ± 1.85 g and 10.0 ± 1.0 cm) with typical injuries associated to Aeromonas infection were divided into four treatments (in triplicate n=10): untreated fish (negative control), 10 mg L-1 of gentamicin, and 20 or 50 µL L-1 of EO. Fish were maintained in aerated 20 L plastic boxes. After 10 days survival of silver catfish infected with Aermonas sp. and treated with essential oil (50 µL L-1) was greater than 90%.