Activity against Mycobacterium tuberculosis of alkaloid constituents of Angostura bark, Galipea officinalis.

The activity of an ethanolic extract of Galipea officinalis bark against Mycobacterium tuberculosis was shown to reside mainly in the basic alkaloidal fraction although the major part of the alkaloids present were in the neutral fraction. Six alkaloids were isolated from the bark including two other alkaloids not previously reported from G. officinalis and a new quinoline named allocuspareine, whose structure was determined by spectroscopic methods. 1H- and 13C-NMR spectral data for three of these compounds are reported for the first time. Isolation and testing of fractions and individual alkaloids against ten strains of M. tuberculosis showed that all the alkaloids possessed some activity but that the unidentified most polar basic fraction exhibited the greatest effect.

Analysis of aporphine and quinolizidine alkaloids from Caulophyllum thalictroides by densitometry and HPLC.

High-performance liquid chromatographic (HPLC) and densitometry procedures were developed to determine the principal alkaloids in the roots of C. thalictroides. In both techniques the alkaloids content was assessed using cytisine as an internal standard. The purity and identity of the peaks of the alkaloids was examined by diode array detection and by comparison with the standards. The content of individual alkaloids was found to be in the range 0.02-1.1% w/w.

Heteronuclear NMR studies of the chromone alkaloids and revision of the structure of some piperidino-chromone alkaloids.

The 13C-NMR spectra of seven chromone alkaloids isolated from Schumanniophyton magnificum have been obtained. Assignment of signals was carried out with the help of heteronuclear coupling experiments and other correlation techniques on the alkaloids and their acyl derivatives. On the basis of the signals observed the structures of the piperidino-alkaloid schumannificine and its N-methyl and anhydro analogues have been revised to that of a piperidone ring linked to the noreugenin via a carbon-carbon bond and a lactol bridge.

Antiviral activity of natural and semi-synthetic chromone alkaloids.

The activity against human immunodeficiency virus (HIV) and herpes simplex virus (HSV), of the non-polar fraction of a methanolic extract of the rootbark of Schumanniophyton magnificum was found to be present in a fraction containing the chromone secondary amine schumannificine 1. Other chromone alkaloids present in the plant were isolated and tested for inhibition of HIV and HSV infections in C8166 and Vero cells, respectively. Acyl and methyl derivatives were prepared and tested. Of all the compounds tested, schumannificine 1 displayed the greatest activity against HIV, whereas potent anti-HSV activity was observed for a number of its derivatives. The presence of a piperidine ring and unsubstituted hydroxy groups on the molecules seems to favour the anti-HIV activity. The anti-HIV activity is considered to be due to irreversible binding to gp120 rather than inhibition of reverse transcriptase or protease.

Evaluation of the anti-tumour action and acute toxicity of kosins from Hagenia abyssinica.

The kosins are phloroglucinol derivatives isolated from female flowers of Hagenia abyssinica (Rosaceae) and were tested for possible cytotoxic activity in vitro and in vivo against a panel of three transplantable murine adenocarcinomas of the colon of varying growth characteristics and morphology (MAC system). Significant reductions in colony formation were observed in vitro in MAC 15A tumour following 1, 3, 6 and 24 h exposure to all kosins (alpha-kosin, kosotoxin and protokosin). The kosins (kosotoxin and protokosin) were also found to be cytotoxic against MAC tumour cells in vivo in some cases. Kosotoxin was subjected to preliminary toxicity studies in mice. It showed no observable toxicity up to 200 mg kg-1 orally and was found to be toxic at doses in excess of 50 mg kg-1 (i.p.). A single dose of 100 mg kg-1 (i.p.) was lethal for 100% of the animals.

Chromatographic and spectroscopic studies on the constituents in male and female flowers of Hagenia abyssinica.

The phenolic constituents of male and female flowers of Hagenia abyssinica were examined using chromatographic and spectroscopic techniques. Chromatographic analysis of kosins (phloroglucinols) was carried out using TLC, reversed-phase LC and glass-capillary GLC. Purification of the crude kosins was effected by silica gel column chromatography and purification of phenolic acids using ion-exchange resins and preparative TLC on silica gel. The kosins were characterized by TLC, LC, UV, IR, MS and H1 NMR spectroscopy while the phenolic acids were characterized by UV-spectroscopy, TLC and LC. The phenolic acids found were protocatechuic acid, p-hydroxybenzoic acid and vanillic acid. The content of the kosins and phenolic acids was established quantitatively for both male and female flowers.