Screening of plant extracts for antimicrobial and anticancer activities
The screening of several crude plant extracts from Gabon for their antimicrobial and antitumoral activities showed us interesting results. After chromatography separation and purification of the alkaloid extracts from Isolona hexaloba (Annonaceae) roots, followed by spectral data analysis, we characterized two bisbenzylisoquinoline: curine and guattegaumerine [1,2,3].
We then, examined whether these compounds can regulate bacterial stress and growth. Interestingly, both molecules activate the formation of bacterial biofilm. However, none of the two, at concentrations ranging from 10-17 to 10-6 M, showed an effect on Escherichia coli, Bacillus subtilis, or a mucoid strain of Pseudomonas aeruginosa growth.
Using the rat hepatocarcinoma cells (HTC-R) that are resistant to anticancer drugs, we tested the effects of curine and guattegaumerine on the efflux of Rhodamine123 from HTC-R, a substrate for P-glycoprotein encoded by mdr1 gene. Curine and guattegaumerine at 10µM were able to reduce Rhodamine123 efflux by 50% and were not verapamil (Rhodamine efflux inhibitor) competitors.
The cytotoxic effect of curine and guattegaumerine was also evaluated on HTC-R cell growth. No effect was found for concentrations ranging from 10-8 to 10-5 M. In contrast, at 10-4 M, curine and guattegaumerine inhibited cell proliferation by 90 and 70% respectively. Thus, we concluded that due to their antiproliferative effect, these two compounds are not specific substrates for P-glycoprotein but may present potential inhibitors for cell growth in cancer treatment.
References: 1. Dias, C.S. et al. (2002) Planta Med. 68: 1049–1051.
2. Marshall, S.J. et al. (1994) Antimicrob. Agents Chemother. 38: 96–103.
3. Leclercq, J. et al. (1987) Planta Med. 53: 116–117.