Polyhydroxy Acids as Fabaceous Plant Components Induce Oviposition of the Common Grass Yellow Butterfly, Eurema Mandarina.

The common grass yellow butterfly, Eurema mandarina is a Fabaceae-feeding species, the females of which readily oviposit on Albizia julibrissin and Lespedeza cuneata in mainland Japan. We previously demonstrated that the methanolic leaf extracts of these plants, and their highly polar aqueous fractions strongly elicit female oviposition. Furthermore, the three subfractions obtained by ion-exchange chromatographic separation of the aqueous fraction have been found to be less effective alone, but synergistically stimulate female oviposition when combined. This indicates that female butterflies respond to multiple compounds with different acidity. We have previously identified d-pinitol from the neutral/amphoteric subfractions and glycine betaine from the basic subfractions as oviposition stimulants of E. mandarina. The present study aimed to identify active compounds in the remaining acidic subfractions of A. julibrissin and L. cuneata leaf extracts. GC-MS analyses of trimethylsilyl-derivatized samples revealed the presence of six compounds in the acidic subfractions. In bioassays using these authentic chemicals, erythronic acid (EA) and threonic acid (TA) were moderately active in eliciting oviposition responses in E. mandarina, with their d-isomers showing slightly higher activity than their l-isomers. Female responsiveness differed between d-EA and l-TA, the major isomers of these compounds in plants, with the response to d-EA reaching a plateau at concentrations above 0.005% and that to l-TA peaking at a concentration of 0.01%. The natural concentrations of d-EA and l-TA in fresh A. julibrissin and L. cuneata leaves were sufficient to stimulate oviposition. Furthermore, mixing 0.001% d-EA or 0.001% l-TA, to which females are mostly unresponsive, with 0.1% d-pinitol resulted in a synergistic enhancement of the oviposition response. These findings demonstrate that E. mandarina females utilize both polyhydroxy acids, EA and TA, as chemical cues for oviposition.

Isolation and characterization of a novel oligomeric proanthocyanidin with significant anti-cancer activities from grape stems (Vitis vinifera).

Novel proanthocyanidin fractions from grape stem extracts were purified using Amberlite XAD-1180N, Sephadex-LH-20, Toyopearl HW40F and reverse phase high-performance liquid chromatography. Two key compounds were estimated as epigallocatechin-(epicatechin)7 gallate using electron-spray ionization time-of-flight mass spectrometry. Epigallocatechin-(epicatechin)7 gallate (compound 1) showed significant anti-cancer activity in PC-3 prostate cancer cells. In particular, compound 1 suppressed the gene expression of fatty acid-binding protein 5 (FABP5), which is involved in promoting cell proliferation and metastasis in prostate cancer cells.