Bactericidal and fungicidal activity of plant extracts from endemic plants of the Chihuahuan Desert of northern Mexico

A large number of compounds are produced by plants endemic to the arid zones of Mexico. These compounds, which are stored in the roots and aerial parts, include phenolics, terpenoids, flavonoids, alkaloids and amino acids with pharmacological potential. In this work we determined the microbicidal effect of three plants from the Chihuahuan Desert. Methanol and ethanol extracts from the aerial parts of Larrea tridentata (Ses. et Moc ex DC.) Felger & Lowe (Zygophyllaceae), Flourensia cernua DC. (Asteraceae) and Lippia graveolens Kunth. (Verbenaceae) yielded nordihydroguiaretic acid, dehydroflourensic acid [1] and timol. The MeOH and EtOH extracts showed bactericidal and fungicidal activity in a variety of in vitro assays. L. tridentata EtOH extracts were more active against seven bacteria and fourteen fungi that cause infection in humans, plants and their products. The ANOVA showed highly significant differences (P ≤0.01) within the extracts, doses, and the interaction extract x dose. At the low concentration of 125µL/L the antibacterial activity of L. tridentata EtOH extract was evident against Escherichia coli; at 1000µL/L all other six bacteria were inhibited by the same extract. On the other hand, aflatoxins produced by the fungi Aspergillus flavus, A. parasiticus and A. niger have received great attention because of their potent and acute toxicological effects in humans. Our results showed that at 1000µL/L A. niger totally inhibited their mycelia growth. For the same effect, A. flavus and A. parasiticus required 4000µL/L. These results provide evidence that L. tridentata extracts may offer a promising option to antibiotics and synthetic pesticides.

Acknowledgements: This work was partially supported by the Government of Campeche State, Mexico and CONACYT through the project CAMP-2005-C01–045.

Reference : 1. Jasso de Rodríguez, et al. (2006), J. Ind. Crops (In press).