E. Mongelli

Insecticidal activity against Aedes aegypti larvae of some medicinal South American plants.

The insecticidal activity of 11 extracts from nine South American medicinal plants has been studied using the Aedes aegypti larvicidal assay. Eight of the 11 plant extracts studied showed toxicity against the A. aegypti larvae (LC(50)<500 microg/ml). The dichloromethane extracts of Abuta grandifolia and Minthostachys setosa demonstrated high larvicidal activity, the most active being the dichloromethane extract of A. grandifolia, with an LC(50)=2.6 microg/ml (LC(100)= 8.1 microg/ml), indicating an activity 2-fold higher than beta-asarone, a natural botanical insecticide used as a positive control (LC(100)=16 microg/ml). On the other hand, the dichloromethane extract of M. setosa was quite potent against A. aegypti larvae showing an LC(50)=9.2 microg/ml (LC(100)=25.2 microg/ml). The results obtained suggest that the extracts of A. grandifolia and M. setosa are promising as larvicides against A. aegypti larvae and could be useful in the search for new larvicidal natural compounds.

Evaluation of the in vitro antioxidant activity in extracts of Uncaria tomentosa (Willd.) DC.

Different extracts of U. tomentosa were tested in vitro for their antioxidant activity utilizing tert ‐butyl‐hydroperoxide‐initiated chemiluminescence in rat liver homogenates. Methanol fractions of both stem‐bark and roots were capable of exerting antioxidant activity by this technique. The presence of different concentrations of bark and root methanol extracts also prevented TBARS production and free radical‐mediated DNA‐sugar damage.

In vitro antioxidant and cytotoxic activity of extracts of Baccharis coridifolia DC

The in vitro antioxidant and cytotoxic activities in different extracts of Baccharis coridifolia DC. (Compositae) were studied using different bioassays. Antioxidant activity was tested using hydroperoxide-initiated chemiluminescence (CL) in rat liver homogenates. The aqueous extract showed antioxidant activity (IC50 = 141 microg/ml), while the dichloromethane and methanol extracts were prooxidant. Activity in the aqueous extract was confirmed by determination of thiobarbituric acid-reactive substances (TBARS), showing an IC50 = 556 microg/ml. On the other hand, studies on the cytotoxic activity demonstrated a 78% crown gall tumour inhibition and an ED50 = 4. 2 microg/ml in KB cells growth for the dichloromethane extract. A 56% decrease in the initial absorbance of DNA-Methyl Green complex could also be observed at 1000 microg/ml, suggesting the presence of compounds that interact with DNA.

ent-Pimarane type diterpenes from Gnaphalium gaudichaudianum

Fractionation of the methanol extract of Gnaphalium gaudichaudianum DC afforded one new and six known ent-pimarane diterpenes together with velutin, squalene and stigmasterol. The structure of the new compound was established on the basis of extensive 1D and 2D NMR spectroscopic data interpretation. Two of the isolated compounds exhibited moderate toxicity in the Artemia salina toxicity test.

Biological studies of Bolax gummifera, a plant of the Falkland Islands used as a treatment of wounds

Aqueous and dichloromethane extracts of Bolax gummifera (Lam.) Sprengel (Apiaceae), a plant of the Falkland Islands used as a treatment of wounds, were studied in order to support the ethnopharmacological information related to the medicinal use of this plant. The antimicrobial, antioxidant and red blood cells membrane stabilizing activities were analyzed. The antimicrobial bioassay was carried out using the test turbidity method (OD 620 nm), the aqueous extract showing an 82% inhibition of Staphylococcus aureus but no activity against Pseudomonas aeruginosa. The dichloromethane extract inhibited both microorganisms: S. aureus in 94% and P. aeruginosa in 32%. No antioxidant activity could be observed using hydroperoxide-initiated chemiluminescence in rat liver homogenates. Investigations into the membrane stabilizing activity of the extracts were carried out using human red blood cells subjected to hypotonic- and heat-induced lyses. The aqueous extract showed an important stabilizing activity of the red blood cell membrane.

Bioactive Constituents of Conyza Albida

Alkynes and spathulenol were isolated from Conyza albida (Asteraceae); some of the compounds were lethal against Artemia sp. and cytotoxic against KB cells.