Molluscicidal properties of some species of Annona

In search for plant molluscicides for the vector control of schistosomiasis, ethanolic extracts from different parts of six species of the Annonaceae family were evaluated against adult forms and egg masses of Biomphalaria glabrata. Results from accurate experiments indicate that the majority of analyzed extracts possess properties lethal to Biomphalaria glabrata, some of them with significant LD90 values (< 20 ppm), as showed for Annona crassiflora M: [pulp and seed (LD50 = 13.21), steem (2.34), root bark (3.79)], Annona glabra L. [seed (17.02)], Annona muricata [leaf (8.75)]. Emphasis is held mainly into Annona muricata L. (leaf) and Annona squamosa Veil. (root) for presenting additional toxicity toward snail egg masses.

Synthesis, electrochemistry, and molluscicidal activity of nitroaromatic compounds: effects of substituents and the role of redox potential

Abstract-Molluscicidal bioassays and electrochemical studies (measurement of first wave reduction potential, Epcl) were performed on several synthetic nitroaromatics, in relation to possible correlation between biological activity, redox potential and structural effects. Five of them presented a significant molluscicidal activity on Biomphalaria glabrata (LD50 < 20 ppm). The Epc1 values ranged from -0.532 to -0.857 V versus Ag/AgCl (0.1 M) (-0.260 to -0.585 V versus NHE), all of them, in the favorable range for reduction in vivo. Data comparison between Epc1 and molluscicidal activity indicates that the presence of the electroactive nitro group is important for the biological activity. Correlation with redox potential, however, was not evident. Structural effects seem to be the most important parameter. Higher activity is noticeable for phenols, including the para-nitro azo or hydrazo-containing compounds. No activity was observed for compounds having the benzylic substituent in meta position to the nitro group. These results suggest that activity undoubtedly involves more than reduction characteristics and that the possible formation of electrophilic species, after nitro reduction, can play an important role in molluscicidal activity against B. glabrata.

Molluscicidal and trypanocidal activities of lapachol derivatives

The activity of the potassium salt of lapachol against the snail Biomphalaria glabrata and its egg masses was tested. The obtained IC50 values (2.70 ppm and 1.43 ppm, respectively) are indicative of a strong activity. Lapachol derivatives were also assayed against infective trypomastigote blood forms of T. cruzi and the triacetoxy derivative of reduced lapachol showed relevant trypanocidal activity, killing 95.7% of the parasites at the concentration of 42 microg/mL.

Molluscicidal activity of 2-hydroxy-3-alkyl-1,4-naphthoquinones and derivatives

In the search for new molluscicidal agents we tested the activity of lapachol and other 2-hydroxy-3-alkylnaphthoquinones possessing nitrogenated alkyl chains, against the snail Biomphalaria glabrata. Lapachol, isolapachol and nor-lapachol showed strong molluscicidal activity against the adult snail (LD(90)<10 ppm) and significant toxicity against snail egg masses (LD(90)<0.2 ppm). As lapachol is easily extracted, and the derivatives can be synthesised without any difficulty, large-scale synthesis and field tests can be conducted, with a view to large-scale molluscicidal programs.

The molluscicidal activity of plants used in Brazilian folk medicine

In a continuing search for new compounds for the control of the vectors of schistosomiasis, we have tested the activity of some Brazilian medicinal plants as sources of molluscicidal natural compounds, using two molluscicidal bioassays. Twenty-seven crude extracts, from twenty-six species belonging to nineteen families, were tested. Seven extracts showed significant molluscicidal activity against Biomphalaria glabrata adults with DL50 values of less than 50 ppm, and five of them were very active in the test using egg masses. The species most active against B. glabrata adults (LD50 value = 3.65 ppm) and their egg masses (LD50 value = 0.13 ppm) was Derris sp. Annona muricata [LD50 value (adult) = 11.86 ppm and LD50 value (egg) = 49.62 ppm], Jatropha elliptica (from Goiás state) [LD50 value (adult) = 24.80 ppm and LD50 value (egg) = 3.03 ppm] and Renealmia exaltata [LD50 value (adult) = 28.03 ppm and LD50 value (egg) = 21.67 ppm], were also considered promising molluscicidal plants.

Molluscicidal activity of the diterpenoids jatrophone and jatropholones A and B isolated from Jatropha elliptica (Pohl) Muell. Arg

In the search for new molluscicidal natural products, the activity of the crude ethanol extract of the rhizome of Jatropha elliptica (Pohl.) Muell. Arg. was tested. The LC(50) was 13.07 ppm. The fractionation and purification of the extract furnished jatrophone and a mixture of jatropholones A and B, as the main compounds. They were tested against the snail Biomphalaria glabrata. Jatrophone showed an LC(50) of 1.16 ppm as a molluscicide and an LC(50) of 1.14 ppm for the assay of egg mass, while the mixture of jatropholones A and B presented an LC(50) of 58.04 ppm as a molluscicide and was not active against the second assay at a concentration up to 100 ppm.

Differential effects of Mandevilla velutina compounds on paw oedema induced by phospholipase A2 and phospholipase C

This study compares the effect of Mandevilla velutina compounds with some anti-inflammatory drugs against phospholipase A2- and phospholipase C-induced rat hindpaw oedema. Injection of phospholipase A2 (Naja naja, 2.5-20 U/paw) and phospholipase C (Clostridium perfringens, 0.03-0.05 U/paw) caused a dose-and-time-related increase in paw oedema. Compounds MV 8608 (55 mumol/kg) and MV 8612 (32 mumol/kg, i.p.) inhibited phospholipase A2-induced paw oedema without interfering with phospholipase C-induced oedema. Local injection of both M. velutina compounds also partially attenuated the oedema evoked by phospholipases A2 and C. Dexamethasone (1.3 mumol/kg, p.o.) suppressed only phospholipase A2-induced paw oedema, while indomethacin (11 mumol/kg, p.o.) attenuated only the early phase of phospholipase C-induced oedema. By contrast, phenidone (616 mumol/kg, i.p.) inhibited only phospholipase C-induced oedema, while cyproheptadine (31 mumol/kg) and pyrilamine (100 mumol/kg, p.o.) inhibited only phospholipase A2 oedema. Treatment of animals with compound 48/80 markedly suppressed phospholipase A2-induced paw oedema and to a lesser degree the oedema caused by phospholipase C. Our results indicate that there are marked differences regarding the mechanisms underlying the paw oedema responses caused by phospholipase A2 and phospholipase C. In addition, our data show that M. velutina compounds cause potent and long-lasting inhibition of the pro-inflammatory action of phospholipase A2, an effect which may account for their reported anti-inflammatory activities.

Analysis of the vasorelaxant action of jatrophone in the isolated aorta of the rat: influence of potassium channel blockers

The mechanism underlying the relaxant response of rat aortic rings to the diterpene jatrophone was investigated. Jatrophone (3 and 10 microM) did not affect acetylcholine-induced endothelium-dependent relaxations, but caused concentration-dependent inhibition of noradrenaline (NA)-induced concentrations in unrubbed, and to a lesser extent, in denuded rings. Jatrophone (30 microM) fully prevented responses to angiotensin II and NA, while responses to KCl (up to 220 mM) were unaffected. In depolarizing medium (KCl 40 mM), jatrophone (3-30 microM) antagonized Ca(2+)-induced contractions in a concentration-dependent and noncompetitive manner, while verapamil (10-100 nM) caused a concentration-dependent, rightward displacement and depression of the Ca2+ concentration-response curve. Jatrophone (1 to 300 microM) concentration dependently relaxed rat aortic rings precontraction with either NA (1 microM) or KCl (80 mM), yielding EC50 s of 11 and 24 microM, respectively. These relaxant responses to jatrophone were unaffected by glibenclamide (1 microM), but the concentration-response curve was displaced to the right (2- to 8-fold) by other K+ channel blockers such as tetraethylammonium (10 and 30 mM), 4-aminopyridine (3 and 10 mM) or procaine (1 and 3 mM). These results indicate that jatrophone relaxes the rat aorta, at least in part, by activating K+ channels distinct from the ATP-sensitive subtype. Since jatrophone, like verapamil, relaxed preparations contracted with KCl and inhibited Ca(2+)-induced contractions in depolarized preparations, this diterpene may also block Ca2+ influx through voltage-sensitive channels. However, additional actions of jatrophone on receptor-operated Ca2+ channels causing Ca2+ efflux and/or release cannot be fully ruled out.