The Emetine Alkaloids

Abstract

The present listing includes emetine and emetine analogs, all of which incorporate as part of their structures a top isoquinoline portion originating from tyrosine and a lower portion of monoterpenoidal origin. Tubulosine and related bases are also included; these consist of a top isoquinoline portion, a middle portion of monoterpenoidal origin, and a lower pendant indole system originating from tryptophan.The last alkaloid to be mentioned is the recently characterized bharatamine (30), which occupies an anomalous position. Biogenetically, it is related to emetine (1) because its upper moiety emanates from tyrosine and its lower half is very probably of terpenoidal derivation. From a purely structural aspect, however, this compound may be considered a protoberberine, even though it lacks the two oxygenated substituents always present in ring D of the protoberberines. Because of this ambiguity, bharatamine is included in this listing and will also be mentioned in a forthcoming review of the protoberberines.Emetine and emetine analogs occur with certainty in only three plant families: Alangiaceae, Icacinaceae, and Rubiaceae. Psychotria ipecacuanha Stokes (Rubiaceae) is one of the main sources for emetine and its analogs. The name of this plant is synonymous with Cephaelis ipecacuanha Rich, and also with Uragoga ipecacuanha Baill. Similarly, Psychotria granadensis Benth. ex Oerst is synonymous with Uragoga granadensis.Uv data are in nm, and log e values are quoted between parentheses. Ir frequencies are in cm-1. Nmr spectra are at low resolution in CDC13, unless stated otherwise.Chemical shifts are in units. Whenever two or more references are cited, it is usually the first reference that is actually quoted in the tables.The numbering system for emetine (1) is as given below. Several reviews or listings of the emetine alkaloids have appeared in the literature (la-o).

Improved analysis of emetic alkaloids in tissue cultures and regenerates of Cephaelis ipecacuanha by ion pair high performance liquid chromatography

“…Emetine hydrochloride was purchased from Sigma Chemical Co. Cephaeline was iodated from the roots of C. ipecacuanha and purified according to the procedure described previously (Teshima et al, 1984). Protoemetine (3) was isolated from the roots of C. ipecacuanha, purified by silica gel column chromatography and identified by comparison of 'H NMR data with those published by Wiegrebe et al (1984).…”

Thymidylate synthase activity and the cell growth are inhibited by the ?-carboline-benzoquinolizidine alkaloid deoxytubulosine

“…Tubulosine and related bases consist of a top isoquinoline portion of monoterpenoidal origin and a lower pendant indole system originating from tryptophan (21). The mechanism of TS inhibition by these bcarboline-benzoquinolizidine alkaloids is not clearly understood to date.…”

“…The isolated DTB was identified on the basis of comparison of its physical and spectral data with those reported (21).…”

Analysis of alkaloids (indole alkaloids, isoquinoline alkaloids, tropane alkaloids)

“…This isoquinoline alkaloid mainly occurs in three plant families comprising Icacinaceae, Rubiaceae, and Alangiaceae. The main active constituent of ipecac root is emetine (Wiegrebe et al, 1984). Possessing vital biological functions to make emetine is a major constituent to molecular biologists and pharmacologists.…”