Identification of New Cactus Alkaloids in Backebergia militaris by Tandem Mass Spectrometry

Abstract

Tandem mass spectrometry, applied to simple extracts of Backebergia militaris, indicated the presence of a number of new alkaloids, including fully aromatic oxygenated isoquinolines, their di- and tetra-hydro analogs, and beta-phenethylamines. These conclusions were supported by separation using radial tlc and comparison with authentic compounds. Traces of seven alkaloids new to this cactus species were identified; four (3,4,8,11) were known previously from other cacti. Three novel cactus alkaloids were identified and confirmed by synthesis as 7,8-dimethoxy-3,4-dihydroisoquinoline (12, dehydrolemaireocereine), 6,7-dimethoxyisoquinoline (13, backebergine), and 7,8-dimethoxyisoquinoline (14, isobackebergine). The last two compounds are the first simple, fully aromatic, isoquinoline alkaloids to be reported from the Cactaceae. The sensitivity of this approach to new alkaloid discovery is emphasized; the entire project consumed only 10 g of dried plant material.

Lissoclinotoxins E and F, Novel Cytotoxic Alkaloids from a Philippine Didemnid Ascidian.

“…15,16 Purification of the reaction product by C 18 flash chromatography [MeOH/aqueous TFA (0.1%)] yielded the pure TFA salt of 2-(3,4-dimethoxyphenyl)-N,N-dimethylethanamine (3), which has been previously reported in the literature both as a synthetic compound 17,18 and as a natural product. [19][20][21] Although the gross structures for compounds 1 and 2 had been conclusively proven by spectroscopic and chemical degradation methods, the determination of stereochemistry about both tricyclic systems had not been established. Two possible geometric isomers existed for lissoclinotoxin E (1) with the N-alkyl chains orientated either trans or cis to each other about the tricyclic system.…”

Opuntia and Other Cacti: Applications and Biotechnological Insights

“…Flavanoids, as those in cactus pear fruit, are known for their affirmative health-benefits (Knishinsky 1971;Iwashina et al 1984;Wang 1988;Goycoolea and Cárdenas 2003;Tesoriere et al 2004). Cacti are reported to produce alkaloids, which is a characteristic feature of Cactaceae family (Agurell 1969;Rosemberg and Paul 1973;Bruhn and Agurell 1974;Bruhn and Lindgren 1976;Gabermann 1978;Ferrigni et al 1984). Cactus pear also contains antioxidants, primarily pectin, carotenes, betalains, ascorbic acid, quercetina and quercetin derivatives (Table 2).…”

“…Cacti do not need much water and accordingly they exhibit unusual physiological and morphological features (Scheinvar 1995;Le Houerou 2000). Cacti are known to contain several useful chemical compounds having nutritional and medicinal desirable properties (Agurell 1969;Knishinsky 1971;Rosemberg and Paul 1973;Bruhn and Agurell 1974;Bruhn and Lindgren 1976;Ferrigni et al 1984;Wang 1988;Frati et al 1990;Fernandez et al 1992;Kazemini 1994;Sahelian 2001;Fernández-López et al 2002;Alarcon-Aguilar et al 2003;Galati et al 2003;Oliveira and Da Machado 2003;Gentile et al 2004;Sirivardhana and Jeon 2004;Tesoriere et al 2004;Zou et al 2005;Saleem et al 2006). Cacti have been exploited as a cheap, alternate source of food suitable for humans and feed for animals and are cultivated as ornamental crops (Estrada-Luna et al 2008).…”

Characterization of Alkaloids and Other Secondary Metabolites by Multiple Stage Mass Spectrometry

“…This demonstrates the expected effect of improved spectral quality as sample preparation becomes more extensive (48). In a more recent investigation, the mikes instrument was used to identify seven previously unidentified alkaloids in Backebergia militaris (17). Four of the alkaloids, known previously from other cacti, were identified as: N-, methyl-3,4-dimethoxyphenethylamine, N,N-dimethyl-3,4-dimethoxyphenethylamine, Nmethylheliamine (2-methyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline), and 1,2-dehydroheliamine.…”

“…Equally important is the fact that the amount of sample required is drastically reduced. In an early experiment, analysis of a few grams of ground, freshly cut poison hemlock was used to detect the alkaloid coniine (16), while more recently, much smaller size samples have been used to detect new, as well as previously known, alkaloids (17). Detection limits in these types of experiments are 0.001% dry weight, or less.…”