Entry #: 31 Date: 22 January 2018
Section: Phenolic extracts
Topic: Phenolic extracts and pancreatic cancer cells
Type: Original Paper

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OliveNetTM Journal Club

Expert review of literature related to olives and olive oil

D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis

Title

Phytochemical properties and anti-proliferative activity of Olea europaea L. leaf extracts against pancreatic cancer cells

Author(s)

Goldsmith et al

Citation / Year

(1) / 2015

Keywords

Phenolic extracts, olive leaf extract, aqueous extract, green extract, oleuropein, pancreatic cancer cells

Summary

The overall aim of this study was to evaluate the quality and potential anti-cancer effects in cell culture of three different olive leaf extractions. The study was motivated by the accumulated evidence indicating that the Mediterranean diet with consumption of extra-virgin olive oil is associated with numerous health benefits (2-4). In particular, the phenolic component, typified by major phenolics such as oleuropein, is thought to be responsible for the health benefits (5-8). In this context, processing of olives for production of olive oil is associated with significant waste products, including olive leaf, wastewater, and pomace, all of which contain high concentrations of phenolic compounds (9, 10). Therefore, potentially extracting or isolating beneficial compounds from these essentially waste products is very beneficial from both an economic and environmental perspective. For reference, olive leaf constitutes approximately 10% of the material arriving at olive processing mills, and is considered a waste product which is either used as animal feed, or requires burning and disposal (1). In this study, the aim was to prepare crude olive leaf extracts from two different olive cultivars using previously optimised extraction processes.

Key points and implications

Olive leaf extracts were prepared from Corregiola and Frantoio Olea europaea L varieties using, what was referred to by the authors as a “green” aqueous (water) extraction process and either a 50% methanol or 50% ethanol extraction process, which also involved ultrasonication. The total phenolic content, flavonoid and oleuropein content, and antioxidant capacity of the three different crude olive leaf extracts was compared. The findings indicated that there no significant difference between the total phenolic content, flavonoid and oleuropein content, and in antioxidant capacity, in extracts prepared from the two different cultivars, in line with the knowledge that geographic location of the tree is the important factor with respect to phenolic profiles. When comparing the phytochemical properties of the different extraction processes, it was shown that although the flavonoid component was higher in the ethanol (approximately double) extract compared to the water extract, the total phenolic content was similar for all three extraction processes. Similarly, at 200 μg/mL all three crude olive leaf extracts reduced the viability of MiaPaCa-2 prostate cancer cells to less than 1% compared to untreated (control) cells. While there were differences in the cyototoxic potency of which was dependent on the cultivar and extraction process, at 100 μg/mL, all of the extracts were more potent than gemcitabine at its IC50 (concentration required to reduce cell viability by 50%). Gemcitabine is an important frontline anticancer chemotherapeutic (11, 12). Interestingly, when comparing the effect on cell viability of the different extracts at 50 μg/mL, it was shown that the Corregiola water extract was the most potent. Overall, this study provides encouraging preliminary cell culture results, and highlights that “green” water extraction methodologies is an important area for further investigation to produce biologically active extracts with potential health benefits.

Related publications

  1. C. D. Goldsmith et al., Phytochemical properties and anti-proliferative activity of Olea europaea L. leaf extracts against pancreatic cancer cells. Molecules 20, 12992-13004 (2015).
  2. M. Dinu, G. Pagliai, A. Casini, F. Sofi, Mediterranean diet and multiple health outcomes: an umbrella review of meta-analyses of observational studies and randomised trials. European journal of clinical nutrition, (2017).
  3. A. Trichopoulou, T. Costacou, C. Bamia, D. Trichopoulos, Adherence to a Mediterranean diet and survival in a Greek population. The New England journal of medicine 348, 2599-2608 (2003).
  4. P. Viola, M. Viola, Virgin olive oil as a fundamental nutritional component and skin protector. Clinics in dermatology 27, 159-165 (2009).
  5. S. De Nicolo et al., Effects of olive polyphenols administration on nerve growth factor and brain-derived neurotrophic factor in the mouse brain. Nutrition 29, 681-687 (2013).
  6. S. C. Edgecombe, G. L. Stretch, P. J. Hayball, Oleuropein, an antioxidant polyphenol from olive oil, is poorly absorbed from isolated perfused rat intestine. The Journal of nutrition 130, 2996-3002 (2000).
  7. S. Fayyaz et al., Oleuropein Mediated Targeting of Signaling Network in Cancer. Current topics in medicinal chemistry 16, 2477-2483 (2016).
  8. A. Parzonko, M. E. Czerwinska, A. K. Kiss, M. Naruszewicz, Oleuropein and oleacein may restore biological functions of endothelial progenitor cells impaired by angiotensin II via activation of Nrf2/heme oxygenase-1 pathway. Phytomedicine : international journal of phytotherapy and phytopharmacology 20, 1088-1094 (2013).
  9. E. Frankel, A. Bakhouche, J. Lozano-Sanchez, A. Segura-Carretero, A. Fernandez-Gutierrez, Literature review on production process to obtain extra virgin olive oil enriched in bioactive compounds. Potential use of byproducts as alternative sources of polyphenols. Journal of agricultural and food chemistry 61, 5179-5188 (2013).
  10. H. K. Obied et al., Bioactivity and analysis of biophenols recovered from olive mill waste. Journal of agricultural and food chemistry 53, 823-837 (2005).
  11. R. Goess, H. Friess, A look at the progress of treating pancreatic cancer over the past 20 years. Expert review of anticancer therapy, 1-10 (2018).
  12. F. C. Passero, Jr., M. W. Saif, Second line treatment options for pancreatic cancer. Expert opinion on pharmacotherapy 18, 1607-1617 (2017).