RESUMO
A chemical investigation of the endemic relict shrub Tetraena mongolica led to the isolation of four new triterpenes: 11α,12α:13ß,28-diepoxyoleanane-3ß-yl trans-caffeate (1), 3ß-hydroxy-11α,12α-epoxyoleanane-28-al (2), olean-11-en-28-al-3ß-yl trans-caffeate (3), and 28-acetoxy-olean-12-en-3ß-yl trans-caffeate (4). Their structures were elucidated by extensive spectroscopic methods.
Assuntos
Medicamentos de Ervas Chinesas/isolamento & purificação , Saponinas/isolamento & purificação , Triterpenos/isolamento & purificação , Zygophyllaceae/química , Medicamentos de Ervas Chinesas/química , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Saponinas/química , Triterpenos/químicaRESUMO
A family of unusual proteins is deposited in flat, structural platelets in reflective tissues of the squid Euprymna scolopes. These proteins, which we have named reflectins, are encoded by at least six genes in three subfamilies and have no reported homologs outside of squids. Reflectins possess five repeating domains, which are highly conserved among members of the family. The proteins have a very unusual composition, with four relatively rare residues (tyrosine, methionine, arginine, and tryptophan) comprising approximately 57% of a reflectin, and several common residues (alanine, isoleucine, leucine, and lysine) occurring in none of the family members. These protein-based reflectors in squids provide a marked example of nanofabrication in animal systems.