Alfonso Guzmán

Novel inhibitory activity of the Staphylococcus aureus NorA efflux pump by a kaempferol rhamnoside isolated from Persea lingue Nees

OBJECTIVES To isolate a plant-derived compound with efflux inhibitory activity towards the NorA transporter of Staphylococcus aureus. METHODS Bioassay-guided isolation was used, with inhibition of ethidium bromide efflux via NorA as a guide. Characterization of activity was carried out using MIC determination and potentiation studies of a fluoroquinolone antibiotic in combination with the isolated compound. Everted membrane vesicles of Escherichia coli cells enriched with NorA were prepared to study efflux inhibitory activity in an isolated manner. RESULTS The ethanolic extract of Persea lingue was subjected to bioassay-guided fractionation and led to the isolation of the known compound kaempferol-3-O-α-L-(2,4-bis-E-p-coumaroyl)rhamnoside (compound 1). Evaluation of the dose-response relationship of compound 1 showed that ethidium bromide efflux was inhibited, with an IC(50) value of 2 μM. The positive control, reserpine, was found to have an IC(50) value of 9 μM. Compound 1 also inhibited NorA in enriched everted membrane vesicles of E. coli. Potentiation studies revealed that compound 1 at 1.56 mg/L synergistically increased the antimicrobial activity of ciprofloxacin 8-fold against a NorA overexpresser, and the synergistic activity was exerted at a fourth of the concentration necessary for reserpine. Compound 1 was not found to exert a synergistic effect on ciprofloxacin against a norA deletion mutant. The 2,3-coumaroyl isomer of compound 1 has been shown previously not to cause acute toxicity in mice at 20 mg/kg/day. CONCLUSIONS Our results show that compound 1 acts through inhibition of the NorA efflux pump. Combination of compound 1 with subinhibitory concentrations of ciprofloxacin renders a wild-type more susceptible and a NorA overexpresser S. aureus susceptible.

Antimicrobial evaluation of Huilliche plant medicine used to treat wounds

ETHNOPHARMACOLOGICAL RELEVANCE The traditional use of 40 plant species used for treatment of wounds and associated infections by the Huilliche people of Chile was evaluated against bacterial and fungal human pathogens, especially including wound pathogens. MATERIALS AND METHODS The extracts were tested against the fungi Penicillium expansum, Candida albicans and the bacteria Bacillus subtilis, Pseudomonas aeruginosa (four different strains), Staphylococcus aureus, Escherichia coli (four different strains), Streptococcus pneumoniae (four different strains with one being resistance to streptomycin). RESULTS Thirteen of the plant species have interesting antimicrobial activities, with that of Acaena argentea, Aristotelia chilensis, Blechnum chilense, Francoa appendiculta, Gevuina avellana and Laureliopsis philippiana being the most noteworthy. CONCLUSIONS The findings in the manuscript support the traditional use by the Huilliche people, and allow enhanced economical benefit and use by the locals. The results obtained on Acaena argentea, Aristotelia chilensis, Blechnum chilense, Francoa appendiculta, Gevuina avellana and Laureliopsis philippiana are of specific scientific interest, and further studies is needed in order to establish the active constituents of the species.

Chemical Composition and Antibacterial Activity of the Leaf Essential Oil of Baccharis magellanica (Lam.) Pers. and Baccharis elaeoides Remy From Chile

Abstract The essential oil and the MeOH extract of the leaves from Baccharis magellanica and B. elaeoides were found to be active against the bacteria Staphylococcus aureus. Analysis of the leaf essential oil yielded 0.3% v/w and 0.7% v/w, respectively. Analysis by GC-FID and GC/MS established the major constituents of both species. In B. elaeoides the major constituents were γ-cadinene (9.9%), limonene (9.1%), τ-cadinol (8.4%), α-cadinol (8.1%), β-pinene (5.0%), β-patchoulene (4.9%), α-muurolene (4.0%), α-pinene (3.6%), α-calacorene (2.7%), γ-muurolene (2.7%), α-thujene (2.5%), α-cubebene (2.4%) and terpinen-4-ol (2.2%), and in B. magellanica the major constituents were 4-hydroxy- acetophenone (30.5%), massoia lactone (9.2%), α-cadinol (6.5%), γ-eudesmol (4.9%), elemol (3.7%), β-eudesmol (2.5%) and caryophyllene oxide (2.3%).

Evaluation of the antibacterial activity of Chilean plants traditionally used for wound healing therapy against multidrug-resistant Staphylococcus aureus.

Anti-staphylococcal activity of Chilean medicinal plants traditionally used by the Huilliche people for wound healing therapy was evaluated against nine Staphylococcus aureus strains. Three extracts of 26 plant samples (20 species) were evaluated by agar overlay bioautography and MIC determination. Total phenolics and tannins were determined, and the antibacterial contribution of the latter was evaluated. The diffusion assay showed that 17 species were active against susceptible S. AUREUS and that 15 species were active against resistant S. aureus. Removal of tannins from extracts rendered only six species active. MIC-determination showed that 20 extracts had antibacterial activity on all eight strains, and the most potent MIC value was 64 µg/mL. Remarkably, 37 extracts were active against the otherwise multidrug-resistant vanthida strain. Our findings support the wound healing properties of Huilliche medicinal plants and the hypothesis that these plants are promising sources of potential anti-staphylococcal agents towards multidrug-resistant strains.

New bisbenzylisoquinoline alkaloid from Laureliopsis philippiana.

Phytochemical investigation of Laureliopsis philippiana resulted in isolation of a new bisbenzylisoquinoline alkaloid (1) named laureliopsine A. The structure was established by spectroscopic methods, including 2D homo- and heteronuclear NMR experiments. This finding of a bisbenzylisoquinoline alkaloid in Laureliopsis supports its close relationship to Atherosperma and its taxonomic segregation from Laurelia.

Mapuche Herbal Medicine Inhibits Blood Platelet Aggregation

12 plant species traditionally used by the Mapuche people in Chile to treat wounds and inflammations have been evaluated for their direct blood platelet inhibition. Seven of the 12 tested plant species showed platelet inhibitory effect in sheep blood, and four of these were also able to inhibit the ADP- (5.0 μM) and collagen- (2.0 μg/mL) induced aggregations in human blood. These four species in respective extracts (in brackets) were Blechnum chilense (MeOH), Luma apiculata (H2O), Amomyrtus luma (DCM : MeOH 1 : 1) and Cestrum parqui (DCM : MeOH 1 : 1). The platelet aggregating inhibitory effects of A. luma (DCM : MeOH 1 : 1), and L. apiculata (H2O) were substantial and confirmed by inhibition of platelet surface activation markers.

Tea Toxicity and Cholinesterase Inhibition of Huilliche Herbal Medicine

Abstract Eleven species of Huilliche medicinal plants used traditionally against infections and for wound healing were tested for their cholinesterase inhibition activity. Two different teas (a 5–7 min infusion and a 1 h decoction, both in water) were tested for their toxicity against Artemia salina. The results from the present study clearly show that teas boiled for 1 h is much more toxic than teas infused for 5–7 min. These results support the different traditional use of the two teas, where the 1h tea is for external use only. Additionally, significant inhibition of cholinesterase has been observed for MeOH extracts of Acaena argentea, Amomyrtas meli and Pseudopanax laetevirens, with that of A. argentea being the most potent. All findings call for further investigations.