Cyclotides from an Extreme Habitat: Characterization of Cyclic Peptides from Viola abyssinica of the Ethiopian Highlands

As part,of ongoing explorations of the structural diversity of cyclotides, the cyclotide content of a native violet of the East African highlands, Vicila abyssinica (which grows at altitudes up to 3400 M), was studied. Six new cyclotideS, valpy A-E. (1-5) and vary E (6), were isolated and characterized by employing HPLC and MS techniques and quantitative amino acid analysis. Cyclotides 1-5 Were found to have 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.