William E. Campbell

Bioactive alkaloids from Brunsvigia radulosa.

A phytochemical investigation of the bulbs of Brunsvigia radulosa yielded the new alkaloid 1-O-acetylnorpluviine, together with the known structures 1-epideacetylbowdensine, crinamine, crinine, hamayne, lycorine, anhydrolycorin-6-one and sternbergine. All structures were established by spectroscopic evidence. Some of the 13C assignments which were reported for crinamine and hamayne were corrected by means of 2D NMR techniques. In order to provide a further structure for biological testing, crinamine was converted to apohaemanthamine. The alkaloids were tested for activity against two strains of cultured Plasmodium falciparum and for cytotoxicity with BL6 mouse melanoma cells.

Alkaloids from Boophane flava

Abstract Fourteen alkaloids have been isolated from bulbs of Boophane flava . The alkaloids, buflavine, 8- O -demethylbuflavine and montabuphine are reported here for the first time. The structure and stereochemistry of these new alkaloids were established by physical and spectroscopic methods. 1 H and 13 C NMR spectra of epivittatine and epibuphanisine were completely assigned by means of 2-D NMR techniques.

Alkaloids from Brunsvigia josephinæ

Abstract Six alkaloids, 3- O -acetylhamayne, hamayne, crinamine, josephinine, ambelline and stembergine have been isolated from bulbs of Brunsvigia josephinae (Amaryllidaceae). The alkaloid josephinine is reported for the first time. Their structure and stereochemistry were established by physical and spectroscopic methods.

Alkaloids from Crinum macowanii

Eleven alkaloids have been isolated from fresh bulbs of Crinum macowanii (Amaryllidaceae). Macowine is reported here for the first time. The structure and stereochemistry of this new alkaloid as well as of the known ones were determined by physical and spectroscopic methods.

Synthesis of totarol amino alcohol derivatives and their antiplasmodial activity and cytotoxicity

The previously unknown antiplasmodial activity of the plant derived natural product totarol is reported. Novel beta-amino alcohol derivatives based on this natural product were designed, synthesised and evaluated for in vitro antiplasmodial activity and cytotoxicity. These derivatives showed antiplasmodial IC50 values in the range of 0.6-3.0 microM and were equally active against a chloroquine-sensitive and resistant strain of Plasmodium falciparum, while showing little cytotoxicity against a mammalian cell line (CHO). In terms of lead development, two of the compounds based on substituted phenylpiperazine warrant further investigation as potential antiplasmodial leads. In addition to their selective antiplasmodial activity and lack of chloroquine cross-resistance, these compounds are structurally different to any of the available antimalarial drugs.

Alkaloids from Crinum delagoense

Abstract Six alkaloids have been isolated from fresh bulbs of Crinum delagoense . The alkaloids, delagoensine and delagoenine, are reported here for the first time. The structure and stereochemistry of the new alkaloids have been determined by physical and spectroscopic methods. 1 H and 13 C NMR spectra were completely assigned by means of 2D NMR techniques.

A dinitrogenous alkaloid from Cyrtanthus obliquus

The ethanolic extract of bulbs of Cyrtanthus obliquus (L.f.) Ait yielded the new dinitrogenous alkaloid obliquine (1), 3S, 4aS, 11S, 10bS-3,4,4a,13,11,5,6-heptahydro-5[2-(4-hydroxyphenyl)ethyl]-3-methoxy-13-methyl-[1,3-dioxolo[4,5-g]indolo[3,3a-c]-isoquinolin-12-one, together with the five known structures 11alpha-hydroxygalanthamine, 3-epimacronine, narcissidine, tazettine and trisphaeridine. All structures were established using 1D and 2D NMR techniques and HREIMS. The alkaloids were tested for cytotoxicity against two mammalian cell lines and did not show activity at concentrations up to 100 microg/ml.

Alkaloids from Brunsvigia orientalis

Abstract Twelve alkaloids have been isolated from bulbs of Brunsvigia orientalis . 1-Epibowdensine, 1-epidemethoxybowdensine and 1-epidecacetylbowdensine are reported here for the first time. The structure and stereochemistry of these new alkaloids have been determined by physical and spectroscopic methods. The 1 H and 13 C NMR spectra of 6-hydroxycrinamine (both epimers) and crinamidine were completely assigned by means of 2D NMR techniques.

Alkaloids from Cyrtanthus elatus

The alcoholic extract of the fresh bulbs of Cyrtanthus elatus yielded zephyranthine (1) and 1,2-O-diacetylzephyranthine (2), together with three other known alkaloids. Complete assignment of 1H and 13C NMR spectra of compounds 1 and 2 was done by employment of two-dimensional NMR techniques.

Quinolinone alkaloids from an Agathosma species

Abstract The aerial parts of a new species from the genus Agathosma yielded skimmianine and two new alkaloids which were identified by means of spectral data and synthesis as 4,6-dimethoxy-1-methyl-2(1H)-quinolinone and 2,6-dihydro-9-methoxy-2,2,6-trimethyl-5H-pyrano[3,2 c ]quinolin-5-one. Further related structures were synthesized and a 2D NMR study on the eight synthetic structures enabled us to correct some of the data appearing in the literature.