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. 1994 Dec;57(12):1619-25.
doi: 10.1021/np50114a002.

Cyclopsychotride A, a biologically active, 31-residue cyclic peptide isolated from Psychotria longipes

K M Witherup  1 , M J Bogusky, P S Anderson, H Ramjit, R W Ransom, T Wood, M Sardana
Affiliations

Cyclopsychotride A, a biologically active, 31-residue cyclic peptide isolated from Psychotria longipes

K M Witherup et al. J Nat Prod. 1994 Dec.

Abstract

A preliminary characterization is provided of a naturally occurring cyclic peptide with interesting and potent biological activity. A 31-residue cyclic peptide, designated cyclopsychotride A [1], was obtained from the organic extract of the tropical plant, Psychotria longipes. Compound 1 inhibited [125I] neurotensin (NT) binding to HT-29 cell membranes (IC50 3 microM) and also stimulated increased levels of cytosolic Ca2+ in two unrelated cell lines that do not express NT receptors. The peptide was found to dose-dependently increase intracellular Ca2+ at concentrations ranging from 3 to 30 microM, and this response was not blocked by a known NT antagonist. Cyclopsychotride A [1] possesses three disulfide linkages and is thought to be the largest cyclic peptide isolated from a natural source. Both 1H-nmr and cd spectroscopy showed 1 to be highly structured.

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