Cytotoxic activity, lignans

Cytotoxic activity assays were carried out on the lignans (-)-a-conidendrin, (-)-secoisolariciresinol, isotaxiresinol and taxiresinol isolated from Formosan T. mairei, which are also found in several Taxus species, and they exhibited potent cytotoxicity against KB-16, A-549 and HT-29 tumor cell lines [103]. 

In vitro cytotoxic activity was found against human leukemia (HL-60) cells exposed to coumarins (especially dipetaUne) and lignans (asarinin and sesamin) isolated from the root bark and fresh stems of northern prickly ash. Cytotoxic effects on human tumor cell lines were also found from crude extracts of the berries and furanocoumarins isolated therefrom (psoralen, isoimperatoin, and xanthox-toxin). The bark of southern prickly ash has shown in vitro growth inhibition of a methi-cillin-resistant strain of Staphylococcus aureus. Activity was largely attributed to the alkaloid chelerythrine, which showed activity against various other methicillin-resistant strains of the bacteria. ... 

Examples of inhibitors of chromatin function derived from flowering plants (Fig. 80) are etoposide (lignan) and alkaloids camptothecin, Vinca alkaloids, and 7 epitaxol. The rhizome of Podophyllum peltatum L. (May apple, Berberidaceae) has been used to remove warts and to relieve the bowels from costiveness since very early times. It contains podophyllo-toxin, a cytotoxic lignan from which etoposide (Vepesid ), which is used to treat lung cancer, lymphomas, and leukemias on account of its ability to inhibit the activity of... 

The inhibition of proliferation of several cancer cells was investigated with the compounds shown in Fig. 8. One of these lignans, compound 143, was active, having an IC50 of ca. 35 fxmol/1 against HT 29 colon cancer cells [75] and others [76]. This result was in agreement with previously observed cytotoxicities of a-unfunctionalized lactone lignans [77]. 

At least 40 lignans are known to have antitumor and antiviral activity and many are cytotoxic (Ayres and Loike, 1990 Davin et al., 1992 MacRae and Towers, 1984 Mac-Rae et al., 1989), although there are no common structural features to explain this activity. Podophyllotoxin (51) (Fig. 8.15), which has been isolated from a number of plant species, is a potent antineoplastic (i.e., tumor destructive) compound. Although too toxic for practical value, synthetically... 

Many plant phenolics are of pharmaceutical interest. Flavonoids, lignans, flavolignans, coumarins, phenyl pro-panoids, and other phenolic compounds show a wide variety of biological and pharmacological activities, such as anti-oxidant, anti-hepatotoxic, spasmolytic, cytotoxic, anti-fungal, and anti-bacterial. Some flavonoids improve capillary resistance while isoflavonoids found in soy and other legumes have estrogenic activity. 

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