Mariana Meckes

Antiviral activity of Spirulina maxima against herpes simplex virus type 2.

Spirulina has been used in a variety of practical applications in biotechnology and medical sciences. This paper presents the antiviral activity found in a hot water extract (HWE) of a commercial preparation of Spirulina maxima, studied by a microplate inhibition assay, using several viruses. The HWE inhibited the infection for: herpes simplex virus type 2 (HSV-2), pseudorabies virus (PRV), human cytomegalovirus (HCMV), and HSV-1, and the 50% effective inhibition doses (ED(50)) were 0.069, 0.103, 0.142, and 0.333 mg/ml for each virus, respectively. For adenovirus the inhibition was less than 20%, and no inhibition was found for measles virus, subacute sclerosing panencephalitis virus (SSPE), vesicular stomatitis virus (VSV), poliovirus 1 and rotavirus SA-11, at concentrations of 2 mg/ml of the HWE. The highest antiviral activity was for HSV-2, with a selectivity index of 128. The antiviral activity was not due to a virucidal effect. Herpesvirus infection was inhibited at the initial events (adsorption and penetration) of the viral cycle. To initiate the isolation and identification of the compound that exhibits the antiviral activity of S. maxima, some extracts made by using several solvents with different polarity were evaluated by microplate inhibition assay using HSV-2. The highest antiviral activity was detected in the methanol-water 3:1, which suggests that the antiviral activity is probably due to highly polar compounds.

Terpenoids isolated from Psidium guajava hexane extract with depressant activity on central nervous system

A bioguided fractionation of the hexane extract obtained from Psidium guajava leaves led to the isolation of sesquiterpenes with depressant activities on the central nervous system. The results demonstrated that the already reported relaxant properties of Psidium guajava hexane extract are largely due to the presence of terpenes, especially caryophyllene‐oxide and β‐selinene, which were by far the largest single components and potentiated pentobarbital sleeping time and the latency of convulsions induced by leptazol in mice. Calcium concentration‐response curves showed a rightward displacement when the active fraction was added to isolated guinea‐pig ileum depolarized with K+ (60 mm) and cumulative concentrations of CaCl2, suggesting that caryophyllene‐oxide, a known Ca2+ antagonist agent could be responsible for the blockade of extracellular Ca2+ observed with the active fraction.

Antimycobacterial neolignans isolated from Aristolochia taliscana

Tuberculosis (TB - Mycobacterium tuberculosis) is an ancient infectious disease that has appeared once again as a serious worldwide health problem and now comprises the second leading cause of death resulting from a single infection. The prevalence of multidrug resistance (MDR) TB is increasing and therapeutic options for treatment are not always accessible; in fact, some patients do not respond to the available drugs. Therefore, there is an urgent need to develop novel anti-TB agents. The aim of the present study was to screen extracts of Aristolochia taliscana, a plant used in traditional Mexican medicine to treat cough and snake bites, for antimycobacterial activity. The hexanic extract of A. taliscana was tested by microdilution alamar blue assay against Mycobacterium strains and bioguided fractionation led to the isolation of the neolignans licarin A, licarin B and eupomatenoid-7, all of which had antimycobacterial activity. Licarin A was the most active compound, with minimum inhibitory concentrations of 3.12-12.5 microg/mL against the following M. tuberculosis strains: H37Rv, four mono-resistant H37Rv variants and 12 clinical MDR isolates, as well as against five non-tuberculous mycobacteria (NTM) strains. In conclusion, licarin A represents a potentially active anti-TB agent to treat MDR M. tuberculosis and NTM strains.

In vitro susceptibility of Entamoeba histolytica and Giardia lamblia to some medicinal plants used by the people of Southern Mexico

The antiprotozoal properties of six medicinal plants, used by the people of Southern Mexico to treat diarrhoea, were evaluated in vitroagainst Entamoeba histolyticaand Giardia lambliatrophozoites, the most active being the methanol extracts of Rubus coriifolius, Cuphea pinetorumand Helianthemum glomeratum. Further activity guided fractionation of Cuphea pinetorumroots extract led to the isolation of kaempferol and quercetin as the active principles.

The effects of chrysin and pinostrobin, two flavonoids isolated from Teloxys graveolens leaves, on isolated guinea-pig ileum

The pharmacological effects of pinostrobin and chrysin obtained from the aerial parts of Teloxys graveolens (Chenopodiaceae) were evaluated using isolated in vitro guinea-pig ileal smooth muscle. Both flavonoids inhibited the contractions evoked by high concentrations of potassium. The potency of the relaxant effect was determined by measuring the capacity of each product in reducing the phasic and the slower sustained tonic contractile responses induced by depolarization with 60 mM K(+). Concentrations up to 5 × 10(-7) M of pinostrobin and 1 × 10(-7) M of chrysin induced a non-competitive depression of responses to Ca(2+) in ileum preparations bathed in a Ca(2+)-free, high K(+) medium. Both compounds produced a rightward displacement of the concentration-response curves to Ca(2+) with a concentration-dependant increase of EC(50) and a decrease of the maximal response. Examination of the inhibitory effect produced by these flavonoids on the phasic component of contractile response evoked with K(+) and on the contraction induced with caffeine, led to propose a different intracellular mechanism of action used by these compounds. The results obtained led us to conclude that the previously detected relaxant effect of Teloxys graveolens crude extract is due in part, to the presence of chrysin and pinostrobin, which inhibit intestinal smooth muscle contractions by means of a calcium-mediated mechanism. Since the modulation of calcium fluxes in the mucosal epithelium may play a role in antidiarrheal drug action, the observed effects in vitro could in the same way explain the popular use of the plant for the treatment of diarrhea.

Antibacterial properties of Helianthemum glomeratum, a plant used in Maya traditional medicine to treat diarrhoea

Ethnobotanical studies indicate that Helianthemum glomeratum is a plant widely used in Maya communities to treat diarrhoeas. A possible mechanism to counteract infectious diarrhoea would be by inhibiting the growth of the enteropathogen causing the disease. The aim of this work was to study the antimicrobial activity of H. glomeratum against bacterial enteropathogens isolated from faeces of children with acute diarrhoea or dysentery. A methanol extract obtained from the leaves and stems was highly active against Shigella spp and Vibrio cholerae; activity against Salmonella spp and Escherichia coli isolates was also present. Acetone/water extract from the roots was also highly active against Shigella and Vibrio isolates. Further chemical fractionation indicated that antibacterial activity was associated with the polyphenolic fraction. Shigella spp causes severe dysentery in children and Vibrio cholerae causes severe watery diarrhoea. Antidiarrhoeal activity of H. glomeratum may be due, at least in part, to the antimicrobial activity of polyphenolics against bacterial enteropathogens commonly associated with the disease.

Screening of Mexican Medicinal Plants for Antiprotozoal Activity – Part II

The activity of the crude extracts from eight medicinal plants used in Mexico to treat gastrointestinal infections were assayed against Entamoeba histolytica and Giardia lamblia axenic trophozoites. Alternanthera repens, Boerhavia coccinea, Flaveria trinervia, Leucaena esculenta, Tournefortia densiflora and Vitex mollis were found to have antiprotozoal activity, with extracts of Tournefortia densiflora being the most potent against both tested organisms.

Antiprotozoal and Antimycobacterial Activities of Pure Compounds from Aristolochia elegans Rhizomes

We analyzed the antimycobacterial activity of the hexane extract of rhizomes from Aristolochia elegans. Some compounds of this extract were purified and tested against a group of drug-resistant Mycobacterium tuberculosis strains. We also evaluated their antiprotozoal activities. The hexane extract was active against M. tuberculosis H37Rv at a MIC = 100 μg mL−1; the pure compounds eupomatenoid-1, fargesin, and (8R,8′R,9R)-cubebin were active against M. tuberculosis H37Rv (MIC = 50 μg mL−1), while fargesin presented activity against three monoresistant strains of M. tuberculosis H37Rv and a MDR clinical isolate of M. tuberculosis (MIC < 50 μg mL−1). Both the extract and eupomatenoid-1 were very active against E. histolytica and G. lamblia (IC50 < 0.624 μg mL−1); in contrast, fargesin and (8R,8′R,9R)-cubebin were moderately active (IC50 < 275 μg mL−1). In this context, two compounds responsible for the antimycobacterial presented by A. elegans are fargesin and cubebin, although others may exert this activity also. In addition to the antimycobacterial activity, the hexane extract has important activity against E. histolytica and G. lamblia, and eupomatenoid-1 is one of the compounds responsible for the antiparasite activity.

Antibacterial Activity of Piqueria trinervia., a Mexican Medicinal Plant Used to Treat Diarrhea

Abstract Intestinal infectious diseases are among the top 10 causes of mortality in Mexico. Children under 5 years of age and adults over 65 years are the most affected; the incidence is greater in rural and indigenous communities. Traditional remedies based on medicinal plants are commonly used; however, the biological activity of many of them has been poorly studied. Thus, we evaluated the antimicrobial activity of the hexane, dichloromethane, ethyl acetate, and methanol extracts of aerial parts and roots of the Piqueria trinervia. Cav. (Asteraceae) plant used to treat diarrhea in Mexico. The extracts were tested in vitro. against 11 strains: Escherichia coli., E. coli. multidrug resistant (MDR), Salmonella typhi., Shigella boydii., Staphylococcus aureus., Staphylococcus epidermidis., Yersinia enterocolitica., Vibrio cholerae. not toxic, Bacillus subtilis., Enterobacter aerogenes., and Enterobacter agglomerans.. The hexane extract obtained from the thick roots was active against the 11 strains. The ethyl acetate extract from the thin roots was active against eight of the strains; poor activity was detected in dichloromethane and methanol extracts.

Flavonoids of the Aerial Parts of Helianthemum Glomeratum

Activity-directed fractionation of the methanol extract of the aerial parts of Helianthemum glomeratum Lag. (Cistaceae) led to the isolation of kaempferol and quercetin as the major amoebicidat compounds. The inactive compound tiliroside was also isolated.