Annojahnin from Annona jahnii: a possible precursor of mono-tetrahydrofuran acetogenins.

A new cytotoxic Annonaceous acetogenin, annojahnin (1), was isolated from the twigs of Annona jahnii (Annonaceae) by bioactivity-directed fractionation using lethality to brine shrimp. Compound 1 represents an unusual type of C-37 Annonaceous acetogenin, lacking either tetrahydrofuran (THF) or epoxide rings, bearing a keto group at C-10, and possessing a double bond located two methylenes away from a vicinal diol. The structure and absolute configuration of 1 were elucidated by 1H and 13C NMR, COSY, and single-relayed COSY and from chemical derivatives. 4-Deoxy-18/21-trans-annomontacin 10-one (4) and 4-deoxy-18/21-cis-annomontacin-10-one (5), two semisynthetic mono-THF acetogenins, were prepared from 1 by reactions that mimic the biogenetic pathways. These acetogenins showed selective cytotoxicities, comparable or superior to adriamycin, among six human solid tumor cell lines. Reduction of the 10-keto of 1, to the racemic 10-OH derivative (3), retained the bioactivities as did the conversion of 1 to 4 and 5.

Bioactive furonaphtoquinones from Tabebuia barbata (Bignoniaceae).

Tabebuia barbata (E. Mey) Sandw. (Bignoniaceae), locally known as "palo de arco", is indigenous to the upper Orinoco and Amazonas rivers. Brine shrimp lethality-directed fractionation and extensive column chromatography, normal-phase preparative TLC and normal-phase HPLC separation of the ethanol extract of the bark of this previously uninvestigated species has led to the isolation of five active compounds 1-5. The combined spectral evidence (UV, IR, 1H and 13C NMR and mass) identified these compounds as naphthoquinones. These compounds, characterized as lapachol (1), 2-acetylnaphtho-[2,3-b]-furan-4,9-dione (2), 2-acetyl-5-hydroxy-naphtho-[2,3-b]-furan-4,9-dione (3), 2-acetyl-8-hydroxy-naphtho-[2,3-b]-furan-4,9-dione (4), and (+)-8-hydroxy-2(1-hydroxy-ethyl) naphtho-[2,3-b]-furan-4,9-dione (5), were reported previously from other species of the genus Tabebuia but not from T. barbata. Compounds 2-5, reference adriamycin, were significantly cytotoxic against A-549 human lung adeno-carcinoma, MCF-7 human breast carcinoma, and HT-29 human colon carcinoma cells. The compounds isolated (1-5) were also shown to be inhibitors of electron transport in rat liver mitochondria, reference to rotenone, with IC50 values in the range of 15 microM to 82.5 microM. In addition, this study demonstrated that screening and activity-directed fractionation, using brine shrimp lethality as a simple and inexpensive bioassay, can effectively lead to potential antitumor compounds.

Venezenin: a new bioactive Annonaceous acetogenin from the bark of Xylopia aromatica.

Asimicin and a new cytotoxic Annonaceous acetogenin, venezenin [1], were isolated from the bark of Xylopia aromatica by bioactivity-directed fractionation using lethality to brine shrimp. Compound 1 represents an unusual type of C37 Annonaceous acetogenin, lacking either tetrahydrofuran (THF) or epoxide rings and possessing a double bond located two methylenes away from a vicinal diol in the hydrocarbon chain. The structure of 1 was elucidated by 1H- and 13C-nmr, COSY, single-relayed COSY, and by HMBC techniques, and derivatization. Annomontacin 10-one [6] and 18/21-cis-annomontacin-10-one [7], two semi-synthetic mono-THF acetogenins were prepared from 1. These acetogenins showed cytotoxicity, comparable or superior to adriamycin, against three human solid tumor cell lines. Reduction of the 10-keto of 1 to the racemic OH-10 derivative enhanced the bioactivity, as did the conversion of 1 to 6 and 7. Venezenin [1], like other Annonaceous acetogenins, showed inhibition of oxygen uptake by rat liver mitochondria and demonstrated that the THF ring may not be essential to this mode of action.

Two new bioactive monotetrahydrofuran Annonaceous acetogenins from the bark of Xylopia aromatica.

Xylopien [1] and xylomatenin [2], two new bioactive monotetrahydrofuran Annonaceous acetogenins, have been isolated from an EtOH extract of the bark of Xylopia aromatica, using bioactivity-directed fractionation employing lethality to brine shrimp. These new compounds each have a double bond in the hydrocarbon chain and have been identified as C-23, C-24 dehydro analogs of xylopiacin and xylomaticin. Their structures were elucidated by spectral analyses of the parent compounds and/or simple chemical derivatives. Their absolute stereochemistries have been established by 1H- and 2D nmr experiments utilizing the production of Mosher esters. These acetogenins showed cytotoxic potencies superior to adriamycin against three human solid tumor cell lines.

Bioactive annonaceous acetogenins from the bark of Xylopia aromatica.

Bioactive Annonaceous acetogenins have been isolated from the EtOH extract of the bark of Xylopia aromatica by bioactivity-directed fractionation using lethality to brine shrimp. These acetogenins include xylopianin [1 , xylopiacin [2], and xylomaticin [3], which are three new mono-tetrahydrofuran ring type acetogenins, in addition to the known compounds, annomontacin, gigantetronenin, gigantetrocin A, and annonacin. Compounds 1 and 2 are unusual in having hydroxylation at C-8; 3 has the same functionalities as annonacin but with 37 carbons instead of 35 carbons. The structures were elucidated by spectral analysis of the parent compounds and/or simple chemical derivatives. These acetogenins showed cytotoxicities, comparable to adriamycin, against three human solid tumor cell lines.

3 beta-O-palmityl longispinogenin from Trichocereus chilensis.

From the aerial parts of Trichocereus chilensis a new triterpenetriol fatty acid ester was isolated. Its structure was shown to be 3 beta-O-palmityl longispinogenin (olean-12-ene-3 beta,16 beta,28-triol-3-palmitate) [1] by chemical and spectroscopic methods. Compound 1 is inactive in brine shrimp lethality and cytotoxicity bioassays.

Cactus alkaloids. XLVII. N alpha-dimethylhistamine, a hypotensive component of Echinocereus triglochidiatus.

Echinocereus triglochidiatus Engelm. var. neomexicanus (Standley) Standley ex W. T. Marshall is believed to cause psychotropic effects when consumed by the Mexican Tarahumara Indians. A phytochemical study was initiated with E. triglochidiatus Engelm. var. paucispinus Engelm. ex W. T. Marshall, which is more abundant in Texas. In the fractionated extracts three compounds, detected by thin-layer chromatography, were positive to Ehrlich's reagent, indicating the possible presence of indole alkaloids; however, a non-Erhlich positive alkaloid was crystallized as the dihydrochloride and subsequently identified (spectrometrically and via synthesis as N alpha, N alpha-dimethylhistamine dihydrochloride. The same compound was then detected chromatographically in the neomexicanus variety. This compound has peripheral hypotensive effects similar to histamine, and this action may help to explain the alleged psychotrophic effects of the cactus.

Cactus alkaloids XLII: 3,4-dimethoxy-beta-phenethylamine and heliamine from the Mexican cereoid Backebergia militaris.

Backebergia militaris (Andot) Bravo ex Sánchez Mejorada yielded alkaloid crystals from a fractionated ethanol extract of only 20 g of plant material. The alkaloid was identified as heliamine (6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) hydrochloride. A second alkaloid, 3,4-dimethoxy-beta-phenethylamine hydrochloride, was crystallized after preparative TLC of the mother liquors. Both compounds were isolated previously from other cactus species.

Cactus alkaloids. XXXVI. Mescaline and related compounds from Trichocereus peruvianus.

Agurell has previously detected (tlc, glc-ms) tyramine, 3-methoxytyramine, and two unknown alkaloids in the Peruvian cactus, Trichocereus peruvianus Br. and R. The presence of mescaline in other similar Trichocereus species prompted us to reinvestigate this species, which is commercially available in the United States. The nonphenolic alkaloid extracts yielded an abundance of crystalline mescaline hydrochloride (0.82% yield) and a trace of 3,4-dimethoxyphenethylamine (tlc-ms). Crystalline tyramine hydrochloride, 3-methoxytyramine hydrochloride, and 3,5 dimethoxy-4-hydroxphenethylamine hydrochloride were isolated from the phenolic alkaloid extracts; the last compound has not been previously crystallized from nature, although it is the immediate biosynthetic precursor of mescaline. Crystalline 2-chloromescaline hydrochloride was isolated drom the nonphenolic extracts; but, as determined by mass-analyzed ion kinetic energy spectrometry, this new compound is an extraction artifact. Both 2-chloromescaline and 2.6-dichloromescaline hydrochlorides were prepared synthetically from mescaline. This cactus species has a mescaline content equal or superior to peyote and should be legally controlled as an item of drug abuse.

Cactus alkaloids XXXIII: beta-phenethylamines from the Guatemalan cactus Pilosocereus maxonii.

TLC analysis of extracts of Pilosocereus maxonii (Rose) Byles and Rowley detected six identifiable alkaloids. Preparative TLC aided in the crystallization of the hydrochlorides of N-methyl-3,4-dimethoxyphenethylamine, N-methyl-3-methoxytyramine, and N,N-dimethyl-3-methoxytyramine. Traces of 3,4-dimethoxyphenethylamine (TLC and mass spectrometry), tyramine (TLC), and N-methyltyramine (TLC) were identified. While all of these compounds were isolated and/or detected previously in other cactus species, this study is the first reported crystallization of N-methyl- and N,N-dimethyl-3-methoxytyramine from a natural source.

Cactus alkaloids. XXXI. beta-Phenethylamines and tetrahydroisoquinolines from the Mexican cactus dolichothele uberiformis.

A total of ten alkaloids have been identified in extracts of a Mexican cactus, Dolichothele uberiformis (Zucc.) Br. and R. The data provide documentation for the presence of (--)-synephrine, (--)-longimammine, N-methyl-3,4-dimethoxy-beta-phenethylamine, N-methyl-4-methoxy-beta-phenethylamine, (--y-normacromerine, N-methyltryramine, hordenine, longimammatine, and the first reported isolation of (--)-N,N-dimethyl-beta-hydroxy-beta-phenethylamine (ubine) from a natural source. Spectral data support the identification of another new alkaloid (uberine) as 5-methoxy-7-hydroxy-2-methyl-1,2,3,4-tetrahydroisoquinoline.

yote Alkaloids: Identification in the Mexican ictus Pelecyphora aselliformis Ehrenberg.

Hordenine, anhalidine, pellotine, 3-demethyltrichocereine, mescaline, dimethoxy-beta-phenethylamine, and the N-monomethyl derivatives of mescaline d 3,4-dimethoxy-beta-phenethylamine have been isolated or identified, or both, in caloid extracts of a Mexican "peyote" cactus, Pelecyphora aselliformis tenberg. This is the first report of the occurrence of some of these alkaloids, including mescaline, in a North American cactus other than Lophophora.