The chemical investigation of Ledebouria ovatifolia, Clivia caulescens and Haemanthus pauculifolius.
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Date
1999
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Abstract
Ledebouria ovatifolia (Bak.) lessop, Clivia caulescens R.A.Dyer and Haemanthus pauculifolius
Snijman & Van Wyk were the three species investigated in this work.
Ledebouria ovatifolia belongs to the family Hyacinthaceae (Liliaceae sensu lato) and, to date, the
chemical composition of this species has not been investigated. Members of this family are widely
distributed, but are particularly well represented in Southern Africa. The Ledebouria genus was
formerly classified as part of the Scilla genus from which a large number of naturally occurring
oxygen heterocycles known as homoisoflavonoids have been isolated. In this work the bulbs of L.
ovatifolia were investigated and two compounds were isolated. These were the homoisoflavonoid,
5,7-dihydroxy-3-(4'-hydroxybenzyl)-4-chromanone and the chalcone, 6',2'-dimethoxy-4,4'dihydroxychalcone,
both of which are known naturally occurring compounds.
Clivia caulescens and Haemanthus pauculifolius are both members of the Amaryllidaceae family.
The plants of the Amaryllidaceae family form a large group of over sixty genera, which are
concentrated mainly in Southern Africa. Plants from this family have been extensively used in
traditional medicines and many have pharmacological properties. The compounds responsible for
most of these effects are a group of isoquinoline alkaloids, which are found almost exclusively in
plants belonging to this family. The alkaloids isolated from plants belonging to this group are
known to cause poisoning in low doses and can cause excessive salivation and diarrhoea. Higher
doses of the active compounds can cause CNS depression and large enough doses can prove fatal.
Although many of these alkaloids are harmful to man, some of the unique Amaryllidaceae alkaloids
exhibit anti-tumour and anti-viral activities, and are thus potentially beneficial to man.
The Clivia genus is endemic to South Africa and the most common species, C. miniata, is used by
traditional healers to facilitate childbirth and as a snake bite remedy. In this chemical investigation
both the bulbs and the leaves of C. caulescens were investigated. The ethanol extract of the bulbs
yielded four alkaloids, hippeastrine, haemanthamine, lycorine and ll-(S)-hydroxyvittatine. The
investigation of the leaf extract also yielded lycorine and hippeastrine as well as an additional
alkaloid sternbergine.
Haemanthus pauculifilius is a recently described member of the Haemanthus genus, which consists
of 27 taxa that are restricted to Southern Africa and Namibia. In this chemical investigation the
ethanol extract of the bulbs and leaves yielded the common triterpenoid sitosterol as well as two
novel 5,11-methanomorphanthridine type alkaloids, montanine hydrochloride and manthidine.
Description
Thesis (M.Sc.)-University of Natal, Durban, 1999.
Keywords
Ledebouria ovatifolia., Flavonoids., Amaryllidaceae--South Africa., Botanical chemistry., Clivia caulescens., Haemanthus pauculifolius., Plants--analysis., Theses--Chemistry.