Browsing by Author "Johannes, Koehbach"

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    Cyclotide Discovery in Gentianales Revisited—Identification and Characterization of Cyclic Cystine-Knot Peptides and Their Phylogenetic Distribution in Rubiaceae Plants
    (2013-11-04) Johannes, Koehbach; Alfred, F. Attah; Andreas, Berger; Roland, Hellinger; Toni, M. Kutchan; Eric, J. Carpenter; Megan, Rolf; Mubo, A. Sonibare; Jones, O. Moody; Gane, Ka-Shu Wong; Steven, Dessein; Harald, Greger; Christian, W. Gruber
    Cyclotides are a unique class of ribosomally synthesized cysteine-rich miniproteins characterized by a head-to-tail cyclized backbone and three conserved disulfide-bonds in a knotted arrangement. Originally they were discovered in the coffee-family plant Oldenlandia affinis (Rubiaceae) and have since been identified in several species of the violet, cucurbit, pea, potato, and grass families. However, the identification of novel cyclotide-containing plant species still is a major challenge due to the lack of a rapid and accurate analytical workflow in particular for large sampling numbers. As a consequence, their phylogeny in the plant kingdom remains unclear. To gain further insight into the distribution and evolution of plant cyclotides, we analyzed ~300 species of >40 different families, with special emphasis on plants from the order Gentianales. For this purpose, we have developed a refined screening methodology combining chemical analysis of plant extracts and bioinformatic analysis of transcript databases. Using mass spectrometry and transcriptome-mining, we identified nine novel cyclotide-containing species and their related cyclotide precursor genes in the tribe Palicoureeae. The characterization of novel peptide sequences underlines the high variability and plasticity of the cyclotide framework, and a comparison of novel precursor proteins from Carapichea ipecacuanha illustrated their typical cyclotide gene architectures. Phylogenetic analysis of their distribution within the Psychotria alliance revealed cyclotides to be restricted to Palicourea, Margaritopsis, Notopleura, Carapichea, Chassalia, and Geophila. In line with previous reports, our findings confirm cyclotides to be one of the largest peptide families within the plant kingdom and suggest that their total number may exceed tens of thousands.
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    Peptidomics screening for the discovery of uterotonic plant peptides
    (BMC Pharmacology and Toxicology, 2012) Johannes, Koehbach; Alfred, F. Attah; Margaret, O’Brien; Michael, Freissmuth; Christian, W. Gruber
    Drug discovery from natural products is still one of the biggest sources of novel lead compounds. In particular, plant cyclotides, disulfide-rich peptides comprising three conserved disulfide bonds in a knotted arrangement, known as cyclic cystine knot motif, and a head-to-tail cyclization, have been extensively investigated over the last four decades for their use as scaffolds in drug development. However, their distribution among flowering plants still remains limited to few species of the families of Rubiaceae (coffee), Violaceae (violet), Cucurbitaceae (cucurbit), Fabaceae (bean) and recently Solanaceae (potato family), but it is very likely that cyclotides are more widely distributed since their predicted number in Rubiaceae alone is ~50.000. Additionally, the pharmacological validation of plants used in traditional medicines may trigger the discovery of novel uterotonic compounds.
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    Uterine contractilityofplantsusedtofacilitatechildbirthin Nigerian ethnomedicine
    (Journal of Ethnopharmacology, 2012-07-03) Alfred, F. Attah; Margaret, O’Brien; Johannes, Koehbach; Mubo, A. Sonibare; Terry, J. Smith; Christian, W. Gruber
    Ethnopharmacological relevance: Pregnant women in Nigeria use plant preparations to facilitate childbirth and to reduce associated pain. The rationale for this is not known and requires pharmacological validation. Aim of study: Obtain primary information regarding the traditional use of plants and analyze their uterine contractility at cellular level. Materials and methods: Semi-structured, open interviews using questionnaires of traditional healthcare professionals and other informants triggered the collection and identification of medicinal plant species. The relative traditional importance of each medicinal plant was determined by its use-mention index. Extracts of these plants were analyzed for their uterotonic properties on an in vitro human uterine cell collagen model. Result: The plants Calotropis procera, Commelina africana, Duranta repens, Hyptis suaveolens, Ocimum gratissimum, Saba comorensis, Sclerocarya birrea, Sida corymbosa and Vernonia amygdalina were documented and characterized. Aqueous extracts from these nine plants induced significant sustained increases in human myometrial smooth muscle cell contractility, with varying efficiencies, depending upon time and dose of exposure. Conclusion: The folkloric use of several plant species during childbirth in Nigeria has been validated. Seven plants were for the first time characterized to have contractile properties on uterine myometrial cells. The results serve as ideal starting points in the search for safe, longer lasting, effective and tolerable uterotonic drug leads.