Yang, Shilin;
(1992)
Phytochemical Studies of Artemisia Annua L.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Artemisia annua L. belongs to the tribe Anthemideae of the Compositae and comprises some 400 species which are widely- distributed, especially in Asia, North America and Europe. A number of species are of medicinal value in traditional medicine and in particular annua has been used in China for centuries for the treatment of liver disease and malaria. In the search for effective novel antimalarial drugs, the sesquiterpene lactone, artemisinin (qinghaosu, QHS) has been isolated previously from A annua. Artemisinin is active against chloroquine-resistant Plasmodium falciparum in the treatment of cerebral malarial. It has been reported that the in vitro antimalarial activity of artemisinin and some of its derivatives is markedly enhanced by the presence of methoxylated flavones such as artemetin and casticin. Hence it was of interest to isolate other methoxylated flavones from A. annua to ascertain the extent to which such compounds may affect the activity of artemisinin. Thirty four flavonoids, including six novel flavonoids, four coumarins and two novel chromene compounds have been isolated and identified during the present investigation. Their structure elucidation is based on spectroscopic analyses (UV, 'H NMR and MS). The following compounds were identified and apart from casticin and scopoletin they have not been reported previously as constituents of A. annua : casticin, chrysoplenetin, chrysosplenol-D, circilineol, penduletin, eupatorin, axillarin, cirsiliol, tamarixetin, rhamnetin. quercetin-3-methylether, cirsimaritin, rhamnocitrin, chrysoeriol, apigenin, luteolin, kaempferol, quercetin, isorhamnetin,luteolin-4' methylether, isokaempferide, quercetagetin-3-methylether, tomentin, astragalin, luteolin-7- glucoside, quercetin-3'-glucoside, isoquercitrin, quercimeritrin,scoparonej fraxetin-8 methylether, and 5,6- dimethoxycoumarin. The following six novel flavonoids and two novel chromenes were also isolated and characterised: quercetagetin-4'-methylether, quercetagetin 3,4'-dimethylether, 5,2',4'-trihydroxy-6,7,5'-trimethoxyflavone, 5,7,8,3'-tetra hydroxy-3,4' dimethoxyflavone, quercetagetin-3-methylether-4'- glucoside, gossypetin-3-methylether-3' glucoside, 2,2,6-tri hydroxychromene and 2,2-dihydroxy-6-methoxychromene. Some of them, e.g., casticin, chrysoplenetin, chrysosplenol-D and circilineol have weak antimalarial activity and can potentiate the in vitro activity of artemisinin against Plasmodium falciparum.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Phytochemical Studies of Artemisia Annua L. |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10124029 |
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