Catechin from Burkea africana Hook. Exhibits in vitro inhibition of human telomerase activity.

There has been an increasing interest in natural products with the ability to inhibit telomerase activity in tumour and cancerous cells. Green tea catechins have been reported previously to inhibit telomerase, but it was unknown whether catechins from other plant sources could exhibit this property. We isolated 2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol (catechin without the presence of a galloyl unit) from the stem bark of B. africana, and tested its ability to inhibit recombinant, partially purified telomerase produced in rabbit reticulocyte lysates. The B. africana catechin inhibited the telomere extension activity of telomerase with an IC50 of approximately 4.7 µg/ml. This finding indicates that the galloyl unit may not be solely responsible for the inhibition of telomerase activity by catechins. This is the first report of the telomerase-inhibiting potential of catechin from the stem bark of B. africana.

Review of the Phytochemical and Pharmacological Studies of the Genus Markhamia.

Natural product compounds obtained from medicinal plants have been great contributions in the discovery of numerous clinically useful drugs. Markhamia species have been reportedly used by many cultures in human and veterinary traditional medicines. The five identified species of Markhamia, that is, Markhamia lutea, Markhamia obtusifolia, Markhamia stipulata, Markhamia tomentosa, and Markhamia zanzibarica have been the subject of chemical investigations that have led to the characterization of their secondary metabolites. Plants of the genus with the identified phytoconstituents, including phenylpropanoid glycosides (PhGs), terpenoids, phytosterols, lignans, quinones, and flavonoids, have been claimed to possess antiviral, antifungal, antiprotozoal, analgesic, antiinflammatory, and cytotoxic activities. In vitro and in vivo pharmacological research studies have reported the validation of the medicinal properties of plants of this genus. The present review analyzes published data from the ethnomedicinal, phytochemical, and pharmacological studies of plants of the genus Markhamia.

Anticonvulsant activity of the methanolic extract of Justicia extensa T. Anders.

ETHNOPHARMACOLOGICAL RELEVANCE: To investigate the anticonvulsant activity of the leaf extract of Justicia extensa T. Anders used traditionally in the treatment of convulsion. MATERIALS AND METHODS: The anticonvulsant activity of the methanolic extract of Justicia extensa (50, 100 and 200 mg/kg, p.o.) was assessed in strychnine-induced (STR) and picrotoxin-induced (PCT) convulsion models in mice. Diazepam (1 mg/kg) and phenobarbitone (2 mg/kg) were used as reference drugs respectively. RESULTS: The extract showed no toxicity and significantly prolonged (p<0.01-0.05) the onset and reduced the duration of the seizures induced by picrotoxin (5 mg/kg, i.p.) in a dose dependent manner. Phenobarbitone completely inhibited the seizures in this model. Similarly, in the seizures induced by strychnine (1 mg/kg, i.p.), the extract also prolonged the onset and reduced the duration of the seizures though not in a dose dependent manner. Diazepam failed to inhibit the strychnine-induced seizures. The plant extract however showed a significantly higher anticonvulsant activity at 100 and 200 mg/kg in comparison with diazepam. CONCLUSIONS: The results obtained from this work suggest that Justicia extensa has anticonvulsant activity and this supports the use of the plant traditionally in the treatment of convulsion.