Main active constituents and mechanism of toxicity of raphides from Arisaema erubescens against Oncomelania hupensis.

To find a high-efficiency and environment-friendly biogenic molluscicide against Oncomelania hupensis, and prevent aquatic ecosystem from being contaminated by chemical molluscicides and being toxic. We extracted and purified raphides from the tubers of Arisaema erubescent, and determined the active constituents and molluscicidal activity of the raphides, detoxification enzyme activity, and liver damage. The results showed that the raphides had a strong molluscicidal activity. O. hupensis snails were exposed to the lethal concentration (LC50) of 70.95 mg/L and 44.25 mg/L for treatment with raphides for 48 h and 72 h, respectively. The raphides of molluscicidal activity of the main constituents was as follows: intact raphides > calcium oxalate crystals > AEL (Arisaema erubescens Lectin). The activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in the snail livers increased significantly at the early stage of treatment (24 h), but decreased sharply in the later stage (120 h), compared with that in the control group. The results indicated that after treatment with 1/2 LC50 raphides for 120 h, the activities of POD, SOD, and CAT in the snail livers decreased by 82.5 %, 62.9 %, and 84.7 %, respectively. In addition, electron micrographs have shown that the raphides were needle-shaped crystals and tended to be sharp at both ends (with a groove down both sides) and some were barbed, which caused damage to the snail livers to different extent. Overall, our results indicate that the mechanism of toxicity of raphides against O. hupensis may be that the calcium oxalate crystals pricked the liver surface of snail and produced mechanical damage; and then the harmful protease AEL in the raphides was injected into the liver, which reduced the activities of detoxification enzymes, produced severe toxic reactions and eventually killed the O. hupensis snails.

Screening the Efficacy and Safety of Molluscicides from Three Leaf Extracts of Chimonanthus against the Invasive Apple Snail, Pomacea canaliculata.

Pomacea canaliculata, the invasive snail, is a host of the parasitic nematode Angiostrongylus cantonensis, which has adverse effects on the agriculture system and human health. This work evaluated the molluscicidal activity of petroleum ether extracts (PEEs) from three species of Chimonanthus against the snail P. canaliculate. Pcp (PEE of C. praecox) showed the most effective molluscicide activity. Sixty-one compounds were identified by GC-MS and the main components were terpenoids and fatty acids. The half-lethal concentration (LC50) of Pcp at 24 h (0.27 mg/mL) and 48 h (0.19 mg/mL) was used to evaluate the biochemical alterations in snail tissue. These sublethal concentrations caused the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity to increase, while acetylcholinesterase (AChE) activity decreased. Also, under LC50 treatment, several histological changes were observed in the hepatopancreas and foot of the snail compared with the control group. Moreover, the toxic test in rice demonstrated that Pcp has low toxicity. These results suggest that Pcp could be developed as an effective molluscicide for P. canaliculata control.

The Molluscicidal Activity of Green Synthesized Copper Oxide-Based Annona squamosa Seed Extract Nanoparticles on the Feeding Behavior, Biochemical, Molecular, and Immunohistochemical Alterations of Biomphalaria alexandrina Snails.

Because of their low ecological impact, plant molluscicides have garnered much attention. The work aimed to find out if Annona squamosa (AS) seed extract has a molluscicidal impact on Biomphalaria alexandrina snails and enhances this extract by adding CuO nanoparticles (NPs). Using a scanning electron microscope (SEM), transmission electron microscope (TEM), and PANalytical X'Pert PRO X-ray diffractometer (XRD), the presence of the green A. squamosa-based CuO NPs (AS-CuO NPs) was confirmed. After 24 h of exposure, the half-lethal concentration (LC50) of AS-CuO NPs was more toxic to mature B. alexandrina than the aqueous extract of AS seeds (LC50: 119.25 mg/L vs. 169.03 mg/L). The results show that snails exposed to sublethal doses of AS-CuO NPs at LC10 or LC25 (95.4 or 106.7 mg/L, respectively) had much higher glucose levels and alkaline phosphatase activity than those not exposed. Nevertheless, there was no discernible change in the protein content in general or glycogen phosphorylase production. Histological and immunohistochemical analysis showed that snails exposed to A. squamosa-derived CuO NPs LC10 had shrinking digestive tubules and degeneration as well as vacuolation of many digestive, secretory, ova, and sperm cells, with PCNA expressing positively in the hermaphrodite gland and digestive tubule cells. The toxic profile of green CuO NPs produced by A. squamosa may damage the biological activity of B. alexandrina snails; thus, this compound could be used as a molluscicidal base. Furthermore, B. alexandrina proved to be a useful biomarker of nanomaterial contamination.

[Experimental study on the molluscicidal activity of surfactin against Oncomelania hupensis].

OBJECTIVE: To evaluate the molluscicidal activity of surfactin against Oncomelania hupensis, so as to provide the experimental basis for use of Bacillus for killing O. hupensis. METHODS: O. hupensis snails were collected from schistosomiasisendemic foci of Wuhu City on September 2022, and Schistosoma japonicum-infected snails were removed. Then, 60 snails were immersed in surfactin at concentrations of 2, 1, 0.5, 0.25, 0.125 mg/mL and 0.062 5 mg/mL for 24, 48, 72 hours at 26 °C, while ultrapure water-treated snails served as controls. The median lethal concentration (LC50) of surfactin against O. hupensis snails was estimated. O. hupensis snails were immersed in surfactin at a concentration of 24 h LC50 and ultrapure water, and then stained with propidium iodide (PI). The PI uptake in haemocyte was observed in O. hupensis snails using fluorescence microscopy. RESULTS: The mortality of O. hupensis was 5.0% following immersion in surfactin at a concentration of 0.062 5 mg/mL for 24 h, and the mortality was 100.0% following immersion in surfactin at a concentration of 2 mg/mL for 72 h, while no snail mortality was observed in the control group. There were significant differences in the mortality of O. hupensis in each surfactin treatment groups at 24 (χ2 = 180.150, P < 0.05), 48 h (χ2 = 176.786, P < 0.05) and 72 h (χ2 = 216.487, P < 0.05), respectively. The average mortality rates of O. hupensis were 38.9% (140/360), 62.2% (224/360) and 83.3% (300/360) 24, 48 h and 72 h post-immersion in surfactin, respectively (χ2 = 150.264, P < 0.05), and the 24, 48 h and 72 h LC50 values of surfactin were 0.591, 0.191 mg/mL and 0.054 mg/mL against O. hupensis snails. Fluorescence microscopy showed more numbers of haemocytes with PI uptake in 0.5 mg/mL surfactintreated O. hupensis snails than in ultrapure water-treated snails for 24 h, and there was a significant difference in the proportion of PI uptake in haemocytes between surfactin-and ultrapure water-treated snails (χ2 = 6.690, P < 0.05). CONCLUSIONS: Surfactin is active against O. hupensis snails, which may be associated with the alteration in the integrity of haemocyte membrane.

Experimental study on the molluscicidal activity of surfactin against Oncomelania hupensis / 中国血吸虫病防治杂志

OBJECTIVE@#To evaluate the molluscicidal activity of surfactin against Oncomelania hupensis, so as to provide the experimental basis for use of Bacillus for killing O. hupensis.@*METHODS@#O. hupensis snails were collected from schistosomiasisendemic foci of Wuhu City on September 2022, and Schistosoma japonicum-infected snails were removed. Then, 60 snails were immersed in surfactin at concentrations of 2, 1, 0.5, 0.25, 0.125 mg/mL and 0.062 5 mg/mL for 24, 48, 72 hours at 26 °C, while ultrapure water-treated snails served as controls. The median lethal concentration (LC50) of surfactin against O. hupensis snails was estimated. O. hupensis snails were immersed in surfactin at a concentration of 24 h LC50 and ultrapure water, and then stained with propidium iodide (PI). The PI uptake in haemocyte was observed in O. hupensis snails using fluorescence microscopy.@*RESULTS@#The mortality of O. hupensis was 5.0% following immersion in surfactin at a concentration of 0.062 5 mg/mL for 24 h, and the mortality was 100.0% following immersion in surfactin at a concentration of 2 mg/mL for 72 h, while no snail mortality was observed in the control group. There were significant differences in the mortality of O. hupensis in each surfactin treatment groups at 24 (χ2 = 180.150, P < 0.05), 48 h (χ2 = 176.786, P < 0.05) and 72 h (χ2 = 216.487, P < 0.05), respectively. The average mortality rates of O. hupensis were 38.9% (140/360), 62.2% (224/360) and 83.3% (300/360) 24, 48 h and 72 h post-immersion in surfactin, respectively (χ2 = 150.264, P < 0.05), and the 24, 48 h and 72 h LC50 values of surfactin were 0.591, 0.191 mg/mL and 0.054 mg/mL against O. hupensis snails. Fluorescence microscopy showed more numbers of haemocytes with PI uptake in 0.5 mg/mL surfactintreated O. hupensis snails than in ultrapure water-treated snails for 24 h, and there was a significant difference in the proportion of PI uptake in haemocytes between surfactin-and ultrapure water-treated snails (χ2 = 6.690, P < 0.05).@*CONCLUSIONS@#Surfactin is active against O. hupensis snails, which may be associated with the alteration in the integrity of haemocyte membrane.

An Overview of Synthetic Routes of Pharmaceutically Important Pyranopyrazoles.

Pyranopyrazoles are bicyclic nitrogen-containing heterocycles having broadspectrum bioactivities, which may act as anti-cancer, anti-inflammatory, antibacterial, antifungal, insecticidal and molluscicidal agents. Pyranopyrazoles have become an attractive scaffold for the discovery of new drugs due to the diverse range of bioactivities associated with this nucleus. In this review, we have focused on the medicinal importance of pyranopyrazole derivatives and highlighted different routes for the synthesis of pyranopyrazole derivatives using inexpensive and commonly available starting materials.

Molluscicidal and biochemical effects of green-synthesized F-doped ZnO nanoparticles against land snail Monacha cartusiana under laboratory and field conditions.

The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO (F-ZnO) nanoparticles (NPs) that display high molluscicidal activities against the M. cartusiana land snails via leaf dipping and contact techniques. The effect of lethal concentrations, that kills 50% of exposed snails (LC50) value of the treatments, is examined on the activity of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), enzymes, total protein (TP), total lipids (TL) and cholesterol level of snails, including the histopathological evaluation of the digestive gland and foot of M. Cartusiana. Their molluscicidal activity as poisonous baits under field conditions is also evaluated and compared to the recommended molluscicide, Neomyl. The results show that F- doping dramatically improves the snail control capability of ZnO NPs, and promotes a considerable increase in both ALT and AST enzymes with an enhancement of TL and Cholesterol levels, but a significant decrease in TP content and ALP activity in treated snails compared to the control group. The LC50 values are found to be 1381.55 and 2197.59 ppm using the leaf dipping for F-ZnO and ZnO, while 237.51 and 245.90 ppm can be achieved using the contact technique, respectively. The greenly synthesized F-ZnO and ZnO NPs induce severe histological alterations in the digestive gland and foot of M. cartusiana, including a complete destruction of the digestive tubules. The histological evaluation of the foot of M. cartusiana exposed to ZnO, shows a rupture of the epithelial layer of the foot sole, while F- ZnO NPs causes the folds of the foot becoming deeper and the rupture of epithelial layer. Our field experiments further demonstrate that F-ZnO achieves 60.08% reduction, while ZnO attains 56.39% diminution in snail population compared to the commercial, Neomyl (69.55%), exhibiting great potentials in controlling the harmful land snail populations.

Molluscicides against the snail-intermediate host of Schistosoma: a review.

Schistosomiasis, a neglected tropical disease (NTD), is one of the most prevalent parasitoses in the World. Certain freshwater snail species are the intermediate host in the life cycle of schistosome species. Controlling snails employing molluscicides is an effective, quick, and convenient intervention strategy to prevent the spread of Schistosoma species in endemic regions. Advances have been made in developing both synthetic molluscicides and molluscicides derived from plants. However, at present, the development of molluscicides is not adapted to the actual demand for snails and schistosoma controlling. We undertake a systematic review of exploitation and application of synthetic molluscicides and molluscicides derived from plants to combat intermediate host snails. The detailed molluscicidal activity, structure-activity relationship, structural feature, and possible mechanism of some molluscicides are also highlighted, which may afford an important reference for the design of new, more effective molluscicides with low environmental impact and realize the aim of controlling schistosome at transmission stages.

[Molluscicidal activity of the Bacillus velezensisis Y6 strain against Oncomelania hupensis and its preliminary mechanisms of molluscicidal actions].

OBJECTIVE: To assess the molluscicidal activity of the of Bacillus Y6 strain against Oncomelania hupensis in laboratory, and to preliminarily investigate its mechanisms of molluscicidal actions. METHODS: Biological identification of the Y6 strain was performed based on analysis of its morphological and physiochemical features and homology analysis of the 16S rDNA gene sequence. Bacillus Y6 suspensions were formulated at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL, and the molluscicidal activity of Bacillus Y6 suspensions against O. hupensis was tested in laboratory using the immersion method. In addition, the Bacillus Y6 content and glycogen content were detected in O. hupensis following exposure to Bacillus Y6 suspensions to preliminarily explore the molluscicidal mechanism of the Bacillus Y6 strain against O. hupensis. RESULTS: The colony of the Bacillus Y6 strain appeared non-transparent milky white, and mycoderma was produced on the surface of the nutrient agar liquid medium. The Y6 stain was Gram positive and rod-shaped, and the endospore was located at the center of the Bacillus Y6 strain and appeared an achromatic, transparent and refractive body, which was encapsulated by the Y6 strain. The Y6 strain was positive for the lecithinase test, and the 16S rDNA gene sequence showed a 100% homology with those of multiple B. velezensisis strains, B. amyloliquefaciens and B. subtilis. The Y6 strain was therefore identified as B. velezensisis. Following immersion in the Bacillus Y6 suspensions at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL for 24, 48 h and 72 h, the mortality rates of Oncomelania snails were 28.3%, 31.7% and 81.6%, 43.3%, 58.3% and 93.3%, and 63.3%, 78.3% and 98.3%, respectively. The molluscicidal activity of the Bacillus Y6 suspensions increased with the suspension concentration and duration of immersion. Microscopy and colony counting revealed the highest Y6 content in dead snails and the lowest in living snails following immersion in Bacillus Y6 suspensions, and the mean glycogen contents were (0.68 ± 0.06), (1.09 ± 0.16) µg/mg and (2.56 ± 0.32) µg/mg in the soft tissues of dead, dying and living snails following immersion in Bacillus Y6 suspensions (F = 59.519, P < 0.05), and the mean glycogen content was significantly higher in living snails than in dead (t = 14.073, P < 0.05) and dying snails (t = 10.027, P < 0.05), while the mean glycogen content was significantly higher in dying snails than in dead snails (t = 5.983, P < 0.05). CONCLUSIONS: The B. velezensisis Y6 strain shows a high molluscicidal activity against O. hupensis snails, and its invasion may cause glycogen metabolism disorders, leading to snail death.

Molluscicidal activity of the Bacillus velezensisis Y6 strain against Oncomelania hupensis and its preliminary mechanisms of molluscicidal actions / 中国血吸虫病防治杂志

Objective To assess the molluscicidal activity of the of Bacillus Y6 strain against Oncomelania hupensis in laboratory, and to preliminarily investigate its mechanisms of molluscicidal actions. Methods Biological identification of the Y6 strain was performed based on analysis of its morphological and physiochemical features and homology analysis of the 16S rDNA gene sequence. Bacillus Y6 suspensions were formulated at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL, and the molluscicidal activity of Bacillus Y6 suspensions against O. hupensis was tested in laboratory using the immersion method. In addition, the Bacillus Y6 content and glycogen content were detected in O. hupensis following exposure to Bacillus Y6 suspensions to preliminarily explore the molluscicidal mechanism of the Bacillus Y6 strain against O. hupensis. Results The colony of the Bacillus Y6 strain appeared non-transparent milky white, and mycoderma was produced on the surface of the nutrient agar liquid medium. The Y6 stain was Gram positive and rod-shaped, and the endospore was located at the center of the Bacillus Y6 strain and appeared an achromatic, transparent and refractive body, which was encapsulated by the Y6 strain. The Y6 strain was positive for the lecithinase test, and the 16S rDNA gene sequence showed a 100% homology with those of multiple B. velezensisis strains, B. amyloliquefaciens and B. subtilis. The Y6 strain was therefore identified as B. velezensisis. Following immersion in the Bacillus Y6 suspensions at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL for 24, 48 h and 72 h, the mortality rates of Oncomelania snails were 28.3%, 31.7% and 81.6%, 43.3%, 58.3% and 93.3%, and 63.3%, 78.3% and 98.3%, respectively. The molluscicidal activity of the Bacillus Y6 suspensions increased with the suspension concentration and duration of immersion. Microscopy and colony counting revealed the highest Y6 content in dead snails and the lowest in living snails following immersion in Bacillus Y6 suspensions, and the mean glycogen contents were (0.68 ± 0.06), (1.09 ± 0.16) μg/mg and (2.56 ± 0.32) μg/mg in the soft tissues of dead, dying and living snails following immersion in Bacillus Y6 suspensions (F = 59.519, P < 0.05), and the mean glycogen content was significantly higher in living snails than in dead (t = 14.073, P < 0.05) and dying snails (t = 10.027, P < 0.05), while the mean glycogen content was significantly higher in dying snails than in dead snails (t = 5.983, P < 0.05). Conclusion The B. velezensisis Y6 strain shows a high molluscicidal activity against O. hupensis snails, and its invasion may cause glycogen metabolism disorders, leading to snail death.

Molluscicidal activity of fatty acids in the kernel of Chimonanthus praecox cv. Luteus against the golden apple snail Pomacea canaliculata.

The fatty acid composition of the kernel of Chimonanthus praecox cv. Luteus (FKC) was analyzed by gas chromatography-mass spectrometry (GC-MS), its ability to kill Pomacea canaliculata was detected, and the degree of damage and physiological and biochemical effects of an FKC soaking treatment on the hepatopancreas tissue of P. canaliculata were evaluated. In total, 16 fatty acids were detected in FKC, among which 13 were qualitatively identified; octadecadienoic acid (56.76%) and palmitic acid (17.03%) had the highest contents. After 48 h of treatment with FKC, the hepatopancreas of P. canaliculata had a large area of necrosis. The contents of soluble sugar, soluble protein, and albumin (Alb) in the hepatopancreas of P. canaliculata decreased with increasing FKC concentration. The content of malondialdehyde (MDA) and the activities of cereal third transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (AKP), and acetylcholinesterase (AChE) increased with increasing FKC concentration. The results showed that FKC has an obvious negative effect on the hepatopancreas cell structure and physiological function of P. canaliculata, i.e., has strong molluscicidal activity.

Essential oils as molluscicidal agents against schistosomiasis transmitting snails - a review.

This review aims to describe essential oils with bioactivity on adult snails of the genera Bulinus and Biomphalaria, which are intermediate hosts of schistosomes, and brings together information relating to the importance of molluscicides and the chemical composition and toxicity of such oils for other aquatic species. Analysis of the data of original articles revealed that 50 essential oils obtained from 46 plant species were evaluated for molluscicidal activity against the genera cited. More than 80% of the volatile oils studied were active, according to the criteria of the World Health Organization (LC90 or LC100 ≤100 µg/mL or LC50 <40 µg/mL), and most of the oils came from plants belonging to the Rutaceae, Lamiaceae and Pinaceae. Around 37% of the surveyed plant species were obtained in Brazil and 88% of these plants were collected in the northeast of the country, a region with a high prevalence of schistosomiasis mansoni. The essential oils with the highest toxicity against host snails had high levels of hydrocarbon monoterpenes and oxygenated monoterpenes, which may be responsible for the molluscicidal activity. Some volatile components were subjected to molluscicidal evaluation, and the monoterpene compounds exhibited a significant molluscicide effect. This review confirmed the importance of essential oils as a promising alternative for the development of natural molluscicide products. However, in order to be safe for use at sites where schistosome intermediate hosts are found, information on ecotoxicity is required and, to date, few oils have been tested against non-target aquatic species.

Two new compounds from the roots of Pueraria peduncularis and their molluscicidal effects on Pomacea canaliculata.

Two oleanane-type triterpenoid saponins named pedunsaponin D (1) and pedunsaponin E (2) were isolated from the roots of Pueraria peduncularis. The structures of the new compounds were elucidated based on chemical and physicochemical evidence as follows: pedunsaponin D, 3-O-ß-glucopyranosyl-(1-3)-ß-glucuronopyranosyl-3ß,15α,23α-trihydroxy-11,13(18)-oleanadien-16-one (1); pedunsaponin E, 3-O-ß-glucopyranosyl-(1-2)-ß-glucopy ranosyl(1-2)[ß-glucopyranosyl(1-3)-ß-glucuronopyranosyl]-3ß-hydroxy-16-oxoolean-12-en-30-oic acid (2). The two compounds showed moderate molluscicidal activity.[Formula: see text].

Toxicity of Chimonanthus nitens flower extracts to the golden apple snail, Pomacea canaliculata.

We studied the molluscicidal activity of Chimonanthus nitens extracts on Pomacea canaliculata (Ampullariidae). The degree of hepatopancreatic tissue damage, and its physiological and biochemical effects, was evaluated on individuals exposed to petroleum ether extracts (PEEEs). The PEEEs, ethyl acetate extract (EAEE) and water saturated n-butyl extract (SBEE) of C. nitens also had toxic effects on P. canaliculata but PEEE had the greatest molluscicidal activity. After exposure to PEEE for 24 h, the hepatopancreas of P. canaliculata had a large necrotic area. The levels of soluble sugar, soluble protein and albumin (Alb) in the hepatopancreas of P. canaliculata decreased with increasing PEEE concentration, while the activities of glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and acetylcholinesterase (AchE) increased with increasing PEEE concentration. A total of 29 compounds were identified from the PEEE of C. nitens by gas chromatography-mass spectrometry analysis. The main components were esters (48.13%), alcohols (18.43%) and the compound Chimonanthine (14.70%). The results of the molluscicidal assay, histological experiments and the physiological and biochemical experiments show that the PEEE of C. nitens could potentially be used for P. canaliculata management.

Toxicological effects of Ramalina aspera (lichen) on Biomphalaria glabrata snails and Schistosoma mansoni cercariae.

In this study, the molluscicidal activities against Biomphalaria glabrata and cercaricidal activities against Schistosoma mansoni of the ether extract of Ramalina aspera were evaluated. Additionally, toxicity parameters were evaluated at sublethal doses in terms of the influence of the extract on the fertility and fecundity of snails, as well as morphological alterations and quantification of their immunological cells. A test with Artemia salina was also carried out, in order to verify the environmental toxicity of the compound. The ether extract of R. aspera, in which divaricatic acid was identified as the major compound, demonstrated molluscicidal activity at low concentrations against both embryos (LC90 of 22.78, 24.23, 16.63 and 16.03 µg mL-1 for the gastrula, blastula, trochophore and veliger, respectively) and against adult snails (LC90 of 8.66 µg mL-1), after 24 h of exposure. At the sublethal doses, it was possible to observe a decrease in fecundity and quantitative and morphological changes in the defense cells of the exposed snails. In addition, the extract of R. aspera showed a cercaricidal effect on S. mansoni from the concentration of 5.0 µg mL-1, while showing low toxicity to Artemia salina. The ether extract of R. aspera demonstrated effective molluscicidal activity on embryos and adult snails of the species B. glabrata, cercariae of S. mansoni, and presenting low toxicity on Artemia salina. In this way, it could be considered a promising compound in the development of future molluscicidal and cercaricidal agents, thus helping to combat schistosomiasis.

Molluscicidal effectiveness of Luo-Wei, a novel plant-derived molluscicide, against Oncomelania hupensis, Biomphalaria alexandrina and Bulinus truncatus.

BACKGROUND: Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis. Some plant extracts have shown obvious molluscicidal activity, and a new compound Luo-Wei, also named tea-seed distilled saponin (TDS), was developed based on the saponins extracted from Camellia oleifera seeds. We aimed to test the molluscicidal activity of 4% TDS against the intermediate host snails in China and Egypt, and evaluate its environmental safety to non-target organisms. METHODS: In the laboratory, Oncomelania hupensis, Biomphalaria alexandrina and Bulinus truncatus were exposed to 4% TDS, and the median lethal concentration (LC50) was estimated at 24, 48 and 72 h. In the field, snail mortalities were assessed 1, 2, 3 and 7 d post-immersion with 2.5 g/m3 4% TDS and 1, 3, 7 and 15 d post-spraying with 5 g/m2 4% TDS. In addition, the acute toxicity of 4% TDS to Japanese quail (Coturnix japonica), zebrafish (Brachydanio rerio) and freshwater shrimp (Macrobrachium nipponense) was assessed by estimations of LC50 or median lethal dose (LD50). RESULTS: In the laboratory, the LC50 values of 4% TDS for O. hupensis were 0.701, 0.371 and 0.33 mg/L at 24, 48 and 72 h, respectively, and 4% TDS showed a 1.975 mg/L [corrected] 24 h LC50 against B. alexandrina, and a 1.396 mg/L 24 h LC50 against B. truncatus. Across all study regions, the pooled mortalities of O. hupensis were 72, 86, 94 and 98% at 1, 2, 3 and 7 d, following field immersion of 4% TDS at a dose of 2.5 g/m3, and were 69, 77, 85 and 88% at 1, 3, 7 and 15 d, following field spraying at 5 g/m2, respectively. 4% TDS had moderate toxicity to Japanese quail (7 d LD50 > 60 mg/kg) and to shrimp (96 h LC50 = 6.28 mg/L; 95% CI: 3.53-11.2 mg/L), whereas its toxicity to zebrafish was high (96 h LC50 = 0.15 mg/L; 95% CI: 0.14-0.17 mg/L). CONCLUSIONS: 4% TDS is active against O. hupensis, B. alexandrina and B. truncatus under laboratory and field conditions, and it may be a candidate molluscicide of plant origin.

Molluscicidal activity of cardiac glycosides isolated from Adenium obesum.

BACKGROUND: Terrestrial mollusks are one of most important agricultural pests worldwide. Natural phytochemicals have an extended history as a source of pesticides. This study was planned to isolate molluscicidal active compounds from the stems of Adenium obesum. RESULTS: The benzene-soluble fraction of the hydroethanolic extract displayed the most potent molluscicidal activity against Monacha obstructa among different solvent fractions with a median lethal dose (LD50 ) of 4.91 µg g-1 body weight (bw). The bioactivity-guided chemical exploration of the benzene-soluble fraction led to the isolation of two known cardiac glycosides, cerberin and neriifolin which showed significant molluscicidal activity with LD50 values of 5.39 and 4.3 µg g-1 bw, respectively. CONCLUSION: Isolation of the cardiac glycoside neriifolin from A. obesum and the molluscicidal activity of cerberin and neriifolin against terrestrial snails are reported for the first time. © 2019 Society of Chemical Industry.

Molluscicidal activity of Solidago canadensis L. extracts on the snail Pomacea canaliculata Lam.

Extracts from the aerial parts of Solidago canadensis L. were evaluated for molluscicidal activity against Pomacea canaliculata Lam. using an immersion bioassay method. The petroleum ether fraction of the ethanolic extract (PEEE) from S. canadensis exhibited strong molluscicidal activity. The PEEE mode of action in the hepatopancreas tissue of P. canaliculata was tested at several concentrations. Biochemical parameters, namely, soluble sugar content, protein, malondialdehyde (MDA), acetylcholinesterase (AChE) activity, alanine aminotransferase (ALT), and aspartate transaminase (AST) were significantly decreased or increased after exposure to PEEE for 48 h (p<0.05). Histological assessment results showed that hepatopancreas tissue structure was destroyed by exposure to PEEE. Gas chromatography-mass spectrometry analysis (GC-MS) was used to identify 15 compounds that could contribute to the molluscicidal efficacy of the PEEE. Molluscicidal assay, biochemical tests and histological assessments suggest that the PEEE from S. canadensis has potential utility as a molluscicide.

Ambrosia artemisiifolia as a potential resource for management of golden apple snails, Pomacea canaliculata (Lamarck).

BACKGROUND: Ambrosia artemisiifolia, an invasive weed in Europe and Asia, is highly toxic to the golden apple snail (GAS; Pomacea canaliculata) in laboratory tests. However, little is known about the chemical components of A. artemisiifolia associated with the molluscicidal activity or about its potential application for GAS control in rice fields. This study evaluated the molluscicidal activities of powders, methanol extracts, and individual compounds from A. artemisiifolia against GAS in rice fields and under laboratory conditions. RESULTS: Ambrosia artemisiifolia powders did not negatively affect the growth and development of rice but they reduced damage to rice caused by GAS. Extracts had moderate acute toxicity but potent chronic toxicity. The 24-h 50% lethal concentration (LC50 ) of the extracts against GAS was 194.0 mg L-1 , while the weights, lengths and widths of GAS were significantly affected by exposure to a sublethal concentration (100 mg/mL). Psilostachyin, psilostachyin B, and axillaxin were identified as the most active molluscicide components in the aerial parts of A. artemisiifolia, and the 24-h LC50 values of these purified compounds were 15.9, 27.0, and 97.0 mg/L, respectively. CONCLUSION: The results indicate that chemical compounds produced by A. artemisiifolia may be useful for population management of GAS in rice fields. © 2017 Society of Chemical Industry.

Toxicity of Usnic Acid from Cladonia substellata (Lichen) to embryos and adults of Biomphalaria glabrata.

This study reports the molluscicidal activity of usnic acid isolated from Cladonia substellata Vanio (lichen) on embryos at various stages of development and in adult mollusks of Biomphalaria glabrata. The toxicity of usnic acid was also evaluated through Artemia salina larvae mortality. Usnic acid was extracted with diethyl ether, isolated, purified, and its structure confirmed by analyzing the spectra of proton nuclear magnetic resonance. LC90 for 24 h of exposure were 1.62, 4.45, 5.36, and 4.49 µg mL-1 for blastula, gastrula, trocophore, and veliger embryonic stages, respectively, and 3.45 µg mL-1 for adult snails; LC50 of usnic acid against A. salina was 2.46 µg mL-1. LC90 assessed 7 days after exposure was 2.56 µg mL-1 for adult mollusks. In conclusion, these findings demonstrate that under laboratory conditions usnic acid has teratogenic and molluscicide potential to control the aquatic snail B. glabrata and may prove to be a promising candidate in the search for new molluscicide agents, but further detailed studies on its molluscicidal effect and possible environmental effects are needed.