San Martíns R, Gelmi Claudio, de Oliveira Jaime Vargas, Galo José Luis, Pranto Honorio
Pontificia Universidad Católica de Chile, Department of Chemical and Bioprocess Engineering, Santiago, Chile.
Nat Prod Commun. 2009 Oct;4(10):1327-30.
Pomacea canaliculata snails pose a severe problem to direct seeded rice cultivated in Southern Brazil. Control of this snail is nowadays performed with toxic chemicals such as copper sulfate and fungicides such as fentin. A novel natural molluscicide based on alkali modified quinoa (Chenopodium quinoa) saponins was tested under laboratory conditions. Snails were collected in rice fields close to Porto Alegre (State of Rio Grande do Sul) and in Brusque (State of Santa Catarina, 400 km north of Porto Alegre). In Santa Catarina the product was very effective, while in Porto Alegre it had no effect. This unexpected behavior was probably due to the respiratory habits of the snails under different contents of dissolved oxygen in the water. Near Porto Alegre the water used in rice fields is heavily polluted, with dissolved oxygen levels of 1-2 ppm, and the snails rely primarily on their siphon and lungs to breathe. Since saponin control is probably due to an interaction between saponins with the sterols present in the cell walls in the gills, no control was observed. By contrast, in Santa Catarina the dissolved oxygen level of the water is 5-6 ppm, and the snails remain mostly underwater, breathing with their gills. In this case the snails died within 24 h at a dose of 20 and 30 ppm of product. To test this observation, snails grown in polluted waters were forced to remain underwater in saponin solutions and water (control) preventing the use of their siphon to breathe. The snails exposed to saponin solutions died, while the control snails survived, indicating that they were still able to use their gills to breathe. These results indicate that the use of the saponin product is limited to rice fields not irrigated with heavily polluted waters.
福寿螺给巴西南部种植的直播水稻带来了严重问题。目前，人们使用硫酸铜等有毒化学物质以及三苯基氢氧化锡等杀真菌剂来控制这种螺。一种基于碱改性藜麦（Chenopodium quinoa）皂苷的新型天然杀螺剂在实验室条件下进行了测试。福寿螺采集自阿雷格里港（南里奥格兰德州）附近的稻田以及布鲁斯克（圣卡塔琳娜州，位于阿雷格里港以北400公里处）。在圣卡塔琳娜州，该产品非常有效，而在阿雷格里港则没有效果。这种意外情况可能是由于不同溶解氧含量的水中福寿螺的呼吸习性所致。在阿雷格里港附近，稻田用水受到严重污染，溶解氧水平为1 - 2 ppm，福寿螺主要依靠虹吸管和肺呼吸。由于皂苷的控制作用可能是皂苷与鳃细胞壁中的甾醇相互作用的结果，所以未观察到控制效果。相比之下，在圣卡塔琳娜州，水的溶解氧水平为5 - 6 ppm，福寿螺大多待在水下，用鳃呼吸。在这种情况下，福寿螺在产品剂量为20 ppm和30 ppm时，24小时内死亡。为了验证这一观察结果，将在污染水中生长的福寿螺强制置于皂苷溶液和水（对照）中使其待在水下，阻止它们使用虹吸管呼吸。暴露于皂苷溶液中的福寿螺死亡，而对照福寿螺存活，这表明它们仍能够用鳃呼吸。这些结果表明，皂苷产品的使用仅限于未用严重污染水灌溉的稻田。
