Jonathan TolentinoBiology Department, Skyline College, San Bruno CA

Figure 3. Extract assays against E. coli in lettuce. Bacterial inhibition by R. californicus extract may be due to its residual ethanol. Bacterial growth in lettuce treated with C. pycnocephalus extract was too many to count.

Figure 2. Bacterial growth over 7 days in lettuce treated with extracts. R. californicus results were inconclusive, and therefore omitted.

Evaluation of Native American Herbal ExtractsAs Food Preservatives

Background• Food contamination results in 76 million foodborne diseases in

the U. S. annually, and costs the U. S. economy $10-$83 billion in 2008 (3).

• The rise of foodborne illnesses and concern about chemicals as food preservatives has created interest in finding safe microbial inhibitors.

• Propolis, a resinous mixture collected by bees, reduces bacteria in oriental sausage (1). Rosemary extract and grapefruit seed extract inhibit bacteria in marinated pork (2).

• Native American plants used in traditional medicine have been investigated for antimicrobial properties. Taraxacum officinale, Dipsacus sativus, Carduus pycnocephalus, and Ranunculus californicus extracts inhibit growth of E. coli (4).

Discussion & Conclusions• The decrease in volume of the R.californicus extract after

evaporation was minimal, suggesting that the ethanol did not completely evaporate after five days at 35°C. The volume of T. officinale. C. pycnocephalus and D. sativus extracts after evaporation was approximately equal to their initial rehydration with sterile water, suggesting that the acetone was removed from these extracts.

• Future attempts to test the extracts as a food preservative may involve increasing concentration of the extracts by prolonging evaporation and using more plant per volume.

Literature Cited1. Ali, F. H. et al. 2010. “Propolis as a natural decontaminant and

antioxidant in fresh oriental sausage.” Vet. Ital. 46(2):167-72.

2. Schirmer, B. C. et al. 2010. “Evaluation of natural antimicrobials on typical meat spoilage bacteria in vitro and in vacuum packed pork meat.” J. Food Sci. 75(2):M98-M102.

3. Nyachuba, D. G. 2010. “Foodborne illness: is it on the rise?” Nutr. Rev. 68(5):257-69.

4. Tolentino, J. 2009. “Antimicrobial properties of plants used in Native American Traditional Medicine.” SACNAS National Conference Abstracts 2009, 110.

Carduus pycnocephalus Taraxacum officinale Dipsacus sativus Ranunculus californicus Italian thistle Common dandelion Indian teasel California buttercup

Figure 1. Plants used in food preservative assays.

AcknowledgementsDr. Christine Case, Professor of Biology, Skyline College.Rhia Bordon, Biology Student, Skyline College.Tiffany Reardon, Assistant Director, California MESA.Stephen Fredericks, MESA Director, Skyline College.Patricia Carter, Biology Technician, Skyline College.

Results• The extracts are not effective as prepared. E. coli was able to

grow in lettuce and ground beef treated with extracts (Figure 2).

• The 5-day evaporation at 35°C was neither long nor hot enough to completely remove the ethanol in the R.californicus extract. Inhibition of E. coli growth in lettuce with R.californicus extract is attributed to residual alcohol.

• Meat assays with extracts and control had too much bacterial growth to count (Figure 3).

AbstractFoodborne illness is an important public health problem

worldwide. Risks with continued use of chemicals as food preservatives have prompted a search for safer and more natural alternatives. Several California native plants exhibiting antibacterial properties were hypothesized to help prevent bacterial spoilage caused by Escherichia coli. Taraxacum officinale, Dipsacus sativus, Carduus pycnocephalus, and Ranunculus californicus extracts were evaluated for their ability to prevent E. coli growth on lettuce and ground beef kept at 25°C. Ethanolic and acetone extracts were evaporated and rehydrated with sterile distilled water before being assayed. Bacterial growth was determined using dilution and plate counting.

Bacterial growth in lettuce with extracts was not significantly different compared to the control over the seven day observation. Bacterial growth was too many to count for all meat trials with extracts and the control. Results demonstrated that extracts are not effective against E. coli food spoilage as prepared. Future studies of the extracts may involve steps to increase its effectiveness. Effective extracts can provide a source of much needed food preservatives and antibacterial washes.

AimEvaluate the effectiveness of selected Native American plants against food spoilage bacteria and foodborne pathogens in vitro.

Materials & MethodsExtract preparation1. Flowers of R. californicus and D. sativus and leaves of T.

officinale and C. pycnocephalus (Figure 1) were gathered and weighed. Stems and midveins were removed.

2. Plant parts were ground with mortar and pestle.163 mg/mL ethanolic extracts were made from R. californicus flowers, and 500 mg/mL acetone extracts from T. officinale, C. pycnocephalus leaves and D. sativus flowers. The two solvents used correspond to previous assays that confirmed antimicrobial activity of extracts (4).

3. Extracts were air-evaporated for 5 days at 35°C then rehydrated to the original volume with sterile distilled water, and stored at 5°C.

Bacterial growth in food• 3 g of lettuce were cut and placed in sterile Petri dishes. • Samples were inoculated with 100 E. coli cells.• 10 ml extract (500 mg/mL T. officinale, D. sativus and C.

pycnocephalus extracts, 163 mg/mL R. californicus extract) was added to test plates. 10 mL sterile water was added to controls. 1 mL sterile water was added each day to compensate for volume lost due to sampling. Plates were incubated at 25°C for 7 days.

• Samples were taken after 72 and 168 hrs. and bacterial growth was determined by plate counts.

• Steps 2 through 4 were repeated using 10 g ground beef per assay.

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Jonathan TolentinoBiology Department, Skyline College, San Bruno CA

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