We studied the effect of qualitative and quantitative variation of saponin content in foliar tissues of four European alfalfa (Medicago sativa L.) cultivars (Radius, Sapko, Sitel, Radius line 1) on pea aphid (Acyrthosiphon pisum Harris) development, and the effect of aphid infestation on alfalfa saponin content. Aphids (adult apterae, larvae, and adult alatae) were counted on 3-, 6- and 9-month-old plants (before the first, second and third cutting). Thin-layer chromatography was used to detect and estimate the quantity of the following saponins: 3GlcA, 28AraRhaXyl medicagenic acid; 3Glc, 23Ara, 28AraRhaXylApi zanhic acid (zanhic acid tridesmoside); and 3RhaGalGlcA soyasapogenol B (soyasaponin I). Radius, Sapko, and Sitel contained all three saponins but Radius line 1 did not contain zanhic acid tridesmoside or medicagenic acid glycoside. Saponin content was highest in Radius and lowest in Radius line 1. Regardless of the cultivar, saponin content was higher in aphid-infested than uninfested plants. For all sampling dates, aphid numbers were highest on Radius line 1 and lowest on Radius; that is, aphid numbers were inversely related to saponin content. Alfalfa has a herbivoreinduced defense. Saponin levels increase in the foliage of infested alfalfa. Attempts of plant breeders to reduce saponin content in order to increase alfalfa digestibility for livestock might make the plants more susceptible to aphids and other pests.

The paper reports results of investigations concerning the influence of saponin extract of quillaja on the food choice and development of Colorado potato beetle. Choice tests with the use of potato leaf discs treated and untreated with tested saponins’ extract were made. The influence of the presence of saponins on the food choice and intensity of insect feeding were observed. It was stated that saponins significantly restrain feeding and disturb development of this pest.

Steroidal saponins isolated from many plant species belonging to Monocotyledones display potent cytotoxic activity towards many human tumor cells. We examined the cytotoxic effects of crude Paris quadrifolia extract for the first time, testing isolated saponin-rich fractions against four different human cell lines using the [(3-(4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide (MTT) assay. Cytotoxic activity was tested against human promyelocytic leukemia (HL-60) cells, human cervical adenocarcinoma (HeLa) cells and human breast cancer (MDA-MB-468) cells. Human skin fibroblasts were used as non-neoplastic control cells. Our results show significant activity of the weakly water-soluble solid residue and butanolic fraction against HL-60 and HeLa cells. The solid residue exerted cytotoxicity against all tested cell lines.