https://socictopen.socict.org/files/original/f3499ffa5b942392c7b438572472c5b9.pdf 249b2d0e67af85a60078d87cb68ab084 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Coronavirus Description An account of the resource Dominio científico: Coronavirus Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Steroid Alkaloids from Holarrhena africana with Strong Activity against Trypanosoma brucei rhodesiense Creator An entity primarily responsible for making the resource Charles Okeke Nnadi, Ngozi Justina Nwodo, Marcel Kaiser, Reto Brun, Thomas J. Schmidt Description An account of the resource In our continued search for natural compounds with activity against Trypanosoma brucei, causative agent of human African trypanosomiasis (HAT, “sleeping sickness”), we have investigated extracts from the leaves and bark of the West African Holarrhena africana (syn. Holarrhena floribunda; Apocynaceae). The extracts and their alkaloid-enriched fractions displayed promising in vitro activity against bloodstream forms of T. brucei rhodesiense (Tbr; East African HAT). Bioactivity-guided chromatographic fractionation of the alkaloid-rich fractions resulted in the isolation of 17 steroid alkaloids, one nitrogen-free steroid and one alkaloid-like non-steroid. Impressive activities (IC50 in µM) against Tbr were recorded for 3β-holaphyllamine (0.40 ± 0.28), 3α-holaphyllamine (0.37 ± 0.16), 3β-dihydroholaphyllamine (0.67 ± 0.03), N-methylholaphyllamine (0.08 ± 0.01), conessimine (0.17 ± 0.08), conessine (0.42 ± 0.09), isoconessimine (0.17 ± 0.11) and holarrhesine (0.12 ± 0.08) with selectivity indices ranging from 13 to 302. Based on comparison of the structures of this congeneric series of steroid alkaloids and their activities, structure-activity relationships (SARs) could be established. It was found that a basic amino group at position C-3 of the pregnane or pregn-5-ene steroid nucleus is required for a significant anti-trypanosomal activity. The mono-methylated amino group at C-3 represents an optimum for activity. ∆5,6 unsaturation slightly increased the activity while hydrolysis of C-12β ester derivatives led to a loss of activity. An additional amino group at C-20 engaged in a pyrrolidine ring closed towards C-18 significantly increased the selectivity index of the compounds. Our findings provide useful empirical data for further development of steroid alkaloids as a novel class of anti-trypanosomal compounds which represent a promising starting point towards new drugs to combat human African trypanosomiasis. Date A point or period of time associated with an event in the lifecycle of the resource 2017 Subject The topic of the resource Holarrhena africana, Holarrhena fl oribunda, steroid alkaloid, Trypanosoma brucei rhodesiense, structure-activity relationship, anti-trypanosomal Identifier An unambiguous reference to the resource within a given context DOI: 10.3390/molecules22071129 Source A related resource from which the described resource is derived Molecules Publisher An entity responsible for making the resource available MDPI AG Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Organic chemistry Language A language of the resource EN