Screening of Argentinian plants for pesticide activity.

Aerial parts of 27 plant species native to Argentina were tested in anti-insect, germination inhibition and bactericide bio-assays. In antifeedant assays on Epilachna paenulata larvae, 11 species showed strong feeding deterrent effects (higher than 90% at 200 microg/cm(2)). Twelve plants strongly inhibited the germination of Avena sativa seeds, but only six inhibited Raphanus sativum germination at 10 mg/ml. Four plants showed complete growth inhibition of Escherichia coli at a concentration of 2 mg/ml.

In vitro pediculicidal and ovicidal activity of an extract and oil from fruits of Melia azedarach L.

BACKGROUND: Head louse infestation is difficult to control because of increasing lice resistance to synthetic pediculicidal drugs. OBJECTIVE: To test the activity of extract and oil obtained from fruits of Melia azedarach L. against the head louse Pediculus humanus capitis. METHODS: A filter paper diffusion bioassay was carried out in order to determine the pediculicidal and ovicidal activity of extract and oil from M azedarach L. fruits. RESULTS: Both vegetable products, tested either individually or in combinations, showed high levels of mortality on adult lice, with values ranging between 62.9% and 96.5%. The highest mortality rate was obtained with a combination of 20% ripe fruit extract with 10% ripe fruit oil. A formulation made with both extract and oil at 10% plus the addition of emulsifier and preserving agents showed 92.3% pediculicidal activity. The products were also successful in delaying or inhibiting nymph emergence, with the formulation being the most effective, with a complete inhibition of emergence. LIMITATIONS: Because adult lice are sensitive to starvation and therefore control mortalities are often higher than 20% in tests with field specimens, the results may not reflect the direct effect of the extract. CONCLUSIONS: These results demonstrate the possibility of using Melia products for controlling head lice, which are difficult to control because of their resistance to the currently used anti-louse agents.

Laboratory evaluation of Artemisia annua L. extract and artemisinin activity against Epilachna paenulata and Spodoptera eridania.

Ethanolic extract of aerial parts of Artemisia annua L. and artemisinin were evaluated as anti-insect products. In a feeding deterrence assay on Epilachna paenulata Germ (Coleoptera: Coccinellidae) larvae, complete feeding rejection was observed at an extract concentration of 1.5 mg/cm2 on pumpkin leaf tissue. The same concentration produced a feeding inhibition of 87% in Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae). In a no-choice assay, both species ate less and gained less weight when fed on leaves treated with the extract. Complete mortality in E. paenulata and 50% mortality in S. eridania were observed with extract at 1.5 mg/cm2. Artemisinin exhibited a moderate antifeedant effect on E. paenulata and S. eridania at 0.03-0.375 mg/cm2. However, a strong effect on survival and body weight was observed when E. paenulata larvae were forced to feed on leaves treated at 0.03 and 0.075 mg/cm2. Artemisia annua ethanolic extract of aerial parts at 1.5 mg/cm2 showed no phytotoxic effect on pumpkin seedlings.

Antifungal synergistic effect of scopoletin, a hydroxycoumarin isolated from Melia azedarach L. fruits.

In the continuous search for antifungal compounds from plants, the hydroxycoumarin scopoletin (1) was isolated from seed kernels of Melia azedarach L. from which three other compounds, vanillin (2), 4-hydroxy-3-methoxycinnamaldehyde (3), and (+/-) pinoresinol (4), have also been isolated. Guided fractionation through autobiography on TLC using Fusarium verticillioides (Saccardo) Nirenberg as test organism led to the isolation of 1, which exhibited a minimum inhibitory concentration (MIC) of 1.50 mg/mL in the microbroth dilution method. Despite its own weak activity, when the coumarin was combined with the above-mentioned compounds, a strong enhancement of the antifungal effect was observed, even showing a complete inhibition in the growth of the pathogen when 1 was added at a concentration of up to 5% of its MIC value. The same level of effectiveness was observed when the synthetic antifungal agents Mancozeb and Carboxin were each combined with compounds 1-4, in which cases it became possible to decrease the effective concentrations of these commercial compounds by up to 2.5 and 3%, respectively.

Antifungal effects of different organic extracts from Melia azedarach L. on phytopathogenic fungi and their isolated active components.

Extracts from different parts of Melia azedarach L. were studied as potential antifungal agents for selected phytopathogenic fungi. In a serial agar dilution method, hexanic and ethanolic extracts from fruit, seed kernels, and senescent leaves exhibited fungistatic activity against Aspergillus flavus,Diaporthe phaseolorum var. meridionales, Fusarium oxysporum, Fusarium solani, Fusarium verticillioides, and Sclerotinia sclerotiorum. Both hexanic extract from senescent leaves and ethanolic extract from seed kernel were highly effective on all tested fungi, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 25 mg/mL and 0.5 to 5 mg/mL, respectively. In addition, all of the above-mentioned extracts showed fungicidal activity on these fungi, with ethanolic seed kernel extract being the most active. Three compounds displaying activity against F. verticillioides were isolated from the ethanolic seed kernel extract and were characterized as vanillin (1), 4-hydroxy-3-methoxycinnamaldehyde (2), and (+/-)-pinoresinol (3), with MICs of 0.6, 0.4, and 1.0 mg/mL, respectively. These compounds also showed a synergistic effect when combined in different concentrations, needing four times less concentration to reach complete inhibition in the growth of F. verticillioides.