Influence of volatile and nonvolatile secondary metabolites from soybean pods on feeding and on oviposition behavior of Euschistus heros (Hemiptera: Heteroptera: Pentatomidae).

Identification of chemical compounds extracted from host plants that act as oviposition stimulants for pest insects has gained importance, because of the compounds' potential use in the manipulation of insect behavior in the field. However, for generalist insects, such as phytophagous pentatomids, the chemical basis for the selection of the host is not well-known. Insect response can vary according to the soybean genotypes. Chemical profile of soybean pods of cultivars 'BRS 213', 'BRS 267', 'BR-16', and 'IAC-100' were compared regarding the feeding preference and oviposition of the stink bug Euschistus heros (F.). In the no-choice test, E. heros females showed longer feeding time on pods of BR-16 (132.6 min), followed by BRS 213 (128.0 min), BRS 267 (122.5 min), and IAC-100 (82.9 min). In the choice test, there was no significant difference in the feeding time among cultivars. In the oviposition test, females deposited 60% of eggs on the pods of BRS 267, followed by BRS 213 (27.3%), BR-16 (8.8%), and IAC-100 (3.9%). The chemical profile of BRS 267 including greater presence of reducing sugars and lack of isoflavone forms might explain the preference of E. heros to oviposite on it compared with the remaining cultivars tested.

Changes in isoflavone profiles of soybean treated with gamma irradiation.

Soybean is an important Brazilian agricultural commodity that contains a high concentration of isoflavones. Many studies showed that isoflavones are active in the prevention of many human diseases. However, the correct processing techniques used to prepare the soy foodstuffs are important to maintain the active forms. The objective of this study was to evaluate the effect of gamma irradiation on the isoflavone contents of the defatted soybean flour when compared with soybean molasses, a derivative from the soybean food production. After extracting phenolic compounds with methanol aqueous solution (80%), isoflavones were detected by reverse-phase high-performance liquid chromatography/diode-array detector. The radiation doses of 2 and 5 kGy presented a small effect on the isoflavones content of defatted soy flour. Samples irradiated at 50 kGy showed lower isoflavone contents. The observed reduction in the concentration of isoflavones-daidzein, glycitein and genistein-induced by gamma radiation in soy molasses was not significant in defatted soy flour, thus suggesting that isoflavones in defatted soy flour were not eliminated by gamma radiation at rates up to 50 kGy.

Hydrothermal treatments in the development of isoflavone aglycones in soybean (Glycine max (L. ) Merrill) grains

Estudos foram conduzidos para aumentar isoflavonas agliconas (compostos mais biodisponíveis e mais efetivos na prevenção de doenças crônicas) em grãos de soja. Pré-tratamentos hidrotérmicos dos grãos foram conduzidos a 45, 60 e 85 ºC por 5, 30, e 60 minutos. Duas cultivares de soja BR 36 e IAS 5 (115, e 278 mg/100g de isoflavonas totais, respectivamente), foram usadas nos experimentos. Pré-tratamentos dos grãos a 60 ºC por 60 minutos permitiram um considerável aumento das isoflavonas agliconas. Grãos não tratados de BR 36 e IAS 5 apresentaram 1,2 mg/100g de genisteína. Depois dos tratamentos hidrotérmicos, este composto aumentou para 12 e 53 mg/100g, em cada variedade, respectivamente. Em altas temperatures (85 ºC) houve diminuição das agliconas devido a inativação das enzimas b-glicosidases. Os compostos malonil (térmicamente instáveis), também foram reduzidos sob altas temperaturas. No processamento de alimentos funcionais de soja, pré-tratamentos hidrotérmicos dos grãos, bem como a utilização de cultivares com alto teor de isoflavonas permitirão maior desenvolvimento das formas agliconas.