title: Cyclotides from an extreme habitat: characterization of cyclic peptides from Viola abyssinica of the Ethiopian highlands.
abstract: As part of ongoing explorations of the structural diversity of cyclotides, the cyclotide content of a native violet of the East African highlands, Viola abyssinica (which grows at altitudes up to 3400 m), was studied. Six new cyclotides, vaby A-E (1-5) and varv E (6), were isolated and characterized by employing HPLC and MS techniques and quantitative amino acid analysis. Cyclotides 1-5 were found to have new sequences, and 1-3 have a further novel feature in their sequences, an alanine moiety in loop 2. Two of the cyclotides (1 and 4) also exhibited cytotoxic properties in a flourometric microculture cytotoxicity assay. The findings corroborate the hypothesis that investigating the cyclotide contents of violets growing in diverse environments is a promising approach for extending our knowledge of both the structural and biological diversity of cyclotides.
authors: Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Centre, Box 574, SE-751 23 Uppsala, Sweden.
authors: Mariamawit Y
authors: MY
authors: Yeshak
authors: Robert
authors: R
authors: Burman
authors: Kaleab
authors: K
authors: Asres
authors: Ulf
authors: U
authors: Göransson
mesh_terms: D000595:Amino Acid Sequence; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D047169:Cyclotides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D005002:Ethiopia; D006801:Humans; D017386:Sequence Homology, Amino Acid; D032413:Viola / Q000737:chemistry*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D047169:Cyclotides