Antimicrobial properties of resinous plant extracts from Mexico with agrochemical and pharmaceutical potential

The indiscriminate use of synthetic pesticides (SP) for combating agricultural pests has led to undesirable side effects on environmental quality and human health [1]. Thus, there is a great need to find new options to SP for sustainable agriculture. On the other hand, hardly any group of antibiotics has been introduced into clinical practice to which some bacterium has not developed resistance [2]. Natural plant products offer a better option because of their biodegradable nature and unique modes of action [3]. Keeping this in mind in vitro and in vivo studies were conducted to determine the effect of MeOH and EtOH resin extracts from Larrea tridentata (D.C.) Coville (Zygophyllaceae) and Flourensia cernua D.C. (Asteraceae) against some fungi and bacteria that affect crops, foods and humans. The antimicrobial activity was evaluated using fresh cultures of bacteria prepared by inoculating 5 mL of brain-heart infusion with a loopful of the stock cultures. The tubes were incubated at 30°C for 18–20h.; in the case of fungi they were activated by growth in PDA for 7 to 10 days at 25°C. The Draize method was used in albino rabbits for an in vivo assessment of skin irritation by plant extracts. The results showed that L. tridentata and F. cernua extracts had potent in vitro antimicrobial activities against 8 fungi, 8 bacteria and yeast species tested. The ANOVA showed highly significant differences (P ≤0.01) with the extracts, the doses and on the interaction extract X dose. At high concentrations (20,000µL L^-1) both extracts induced erythema when topically applied to skin rabbit. The most aggressive product was L. tridentata MeOH extract. Based on these results, it is clear that these shrubs from the arid zones of Mexico have potential for the development of organic products that could be useful to support and promote a sustainable agriculture with low environmental impact and for the production of pharmaceutical compounds.

References: 1. Kim, B.S. Hwang BK. (2007). J. Phytopathology 155: 641–653. 2. Sleator, R.D., Hill, C. (2008) Let. App. Microb. 46:143–147. 3. Siddique, YH. et al. (2008)J. Nat. Medicines 62: 52–56.