Browsing by Author "Martin, Ricardo San"

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    Antifungal properties of quinoa (Chenopodium quinoa Willd) alkali treated saponnins against Botrytis cinerea
    (2008) Stuardo, Macarena; Martin, Ricardo San
    Quinoa (Chenopodium quinoa Willd) is a Latin American food staple readily available in large quantities in Peru, Bolivia and Ecuador. The outer husk of the grain is removed prior to consumption to reduce its bitter taste. At present, quinoa husks are considered as a by-product with no commercial value, despite its high content of triterpenoid saponins (20-30%). Due to this, the present work was undertaken to test if quinoa saponins have antifungal properties against Botrytis cinerea and if this activity is enhanced after alkaline treatment, since recent reports indicate that alkaline treatment of quinoa saponins increase their biological activity. Six products were tested against B. cinerea: (1) non-purified quinoa extract, (2) purified quinoa extract, (3) alkali treated non-purified quinoa extract, (4) alkali treated purified quinoa extract, (5) non-purified quinoa extract treated with alkali but without thermal incubation and (6) purified quinoa extract treated with alkali but without thermal incubation. Untreated quinoa extracts showed minimum activity against mycelial growth of B. cinerea. Also, no effects were observed against conidial germination, even at 7 mg saponins/ml. However, when the saponin extracts were treated with alkali, mycelial growth and conidial germination were significantly inhibited. At doses of 5 mg saponins/ml, 100% of conidial germination inhibition was observed, even after 96 h of incubation. Fungal membrane integrity experiments based on the uptake of the fluorogenic dye SYTOX green showed that alkali treated saponins generate membrane disruption, while non-treated saponins had no effects. The higher antifungal activity of alkaline treated saponins is probably due to the formation of more hydrophobic saponin derivatives that may have a higher affinity with the sterols present in cell membranes. (c) 2007 Elsevier B.V. All rights reserved.
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    Efficacy of quinoa (Chenopodium quinoa) saponins against golden apple snail (Pomacea canaliculata) in the Philippines under laboratory conditions
    (ELSEVIER SCI LTD, 2008) Joshi, Ravindra C.; Martin, Ricardo San; Saez Navarrete, Cesar; Alarcon, John; Sainz, Javier; Antolin, Mina M.; Martin, Antonio R.; Sebastian, Leocadio S.
    A novel product for managing Pomacea canaliculata, golden apple snail (GAS), containing quinoa saponins (Chenopodium quinoa), was evaluated under laboratory conditions for the protection of newly sprouted rice seeds. Experimental methods mimicked conditions found in direct-seeded rice cultivation in the Philippines, but with a very high GAS density (90 snails/m(2)). Protection of newly sprouted seeds was directly proportional to saponin concentration in rice water. At 9 and 11 ppm saponin, seedling protection after 48 h against GAS of different sizes was 93% and 95%, respectively. Seedling recovery after 5 d with 11 ppm saponin was 93%. This value declined to 0% and 4%, for the control (untreated) and niclosamide, a synthetic chemical molluscicide, respectively. The results indicated that although niclosamide provides high efficacy against GAS (100% mortality, 24h), it has a serious detrimental effect on rice seedlings. Mean GAS mortality with 11 ppm saponin was low at 24 h (45%), but increased to 94% at 48 h. Thus, seedling protection was probably due to an almost immediate closure of the snail's opercula when exposed to saponin solutions, followed by significant death rates within 24 and 48 h. The product also exhibits ovicidal effects, particularly with 1-5 d old egg masses; older egg masses were less susceptible to the product. The use of 11 ppm saponin slightly affected shoot growth, but this effect disappeared with time and the plants attained normal development. Saponin application rates at 10 ppm saponin in the rice water correspond to ca. 6kg product/ha under cultivation conditions used in the Philippines. These results suggest that quinoa saponins may represent a commercially feasible environmentally benign alternative to synthetic chemical molluscicides against GAS, particularly in direct-seeded rice culture. (C) 2007 Elsevier Ltd. All rights reserved.
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    Novel molluscicide against Pomacea canaliculata based on quinoa (Chenopodium quinoa) saponins
    (ELSEVIER SCI LTD, 2008) Martin, Ricardo San; Ndjoko, Karine; Hostettmann, Kurt
    A novel molluscicide against Pomacea canaliculata snails (Golden apple snail, GAS) based on quinoa saponins (Chenopodium quinoa) is presented. Quinoa is a pseudocereal extensively cultivated and consumed in Bolivia and Peru. The external husk of the grains is removed prior to human consumption due to the bitter taste imparted by their high saponin content (predominantly bidesmosidic, saponins), and constitutes a by-product with no commercial value. When tested against GAS, quinoa husks showed no activity up to 121 ppm product (approximately 35 ppm saponins). To increase their molluscicidal properties, the husks were treated with alkali to convert bidesmosidic saponins to more active monodesmosides. This product killed 100% GAS under laboratory conditions at 24h at approximately 33 ppm product. Surprisingly no toxicity to fish, such as goldfish or tilapia, was observed up to the highest concentration tested (e.g., 54ppm product). This is a main advantage in relation to available commercial molluscicides that kill fish at product doses lower than those that kill GAS (e.g., niclosamide). The product was also tested preliminary under field conditions in Northern Argentina with similar GAS mortality results. A preliminary LC/ESI-MS/MS study revealed that the husks contained a mixture of known and novel bidesmosidic and monodesmosidic saponins. However, the alkali treated husks did not contain monodesmosidic saponins as expected, but large molecular weight saponin derivatives, probably formed between the saponins and other compounds present in the quinoa hulls under alkaline conditions. Due to the complex nature of these compounds, no direct relationship could be established between product efficacy and a higher content of monodesmosidic saponins. The results suggested that the molluscicidal properties are probably related to the formation of more hydrophobic compounds after alkaline treatment that have higher affinity with the cholesterol present in GAS gills. (C) 2007 Elsevier Ltd. All rights reserved.