Pro-Apoptotic and Anti-Angiogenesis Effects of Olive Leaf Extract on Spontaneous Mouse Mammary Tumor Model by Balancing Vascular Endothelial Growth Factor and Endostatin Levels

Antioxidant Extracts from Greek and Spanish Olive Leaves: Antimicrobial, Anticancer and Antiangiogenic Effects

Olea europaea L. is the most valuable species of the Olea type, and its products offer a wide range of therapeutical uses. The olive tree has been extensively studied for its nourishing qualities, and the "Mediterranean diet", which includes virgin olive oil as a key dietary component, is strongly associated with a reduced risk of cardiovascular disease and various malignancies. Olive leaves, a by-product in the olive harvesting process, are valued as a resource for developing novel phytomedicines. For this purpose, two ethanolic extracts obtained from Olivae folium from Spain (OFS) and Greece (OFG) were investigated. Our findings contribute to a wider characterization of olive leaves. Both extracts displayed important amounts of phenolic compounds and pentacyclic triterpenes, OFG having higher concentrations of both polyphenols, such as oleuropein and lutein, as well as triterpenes, such as oleanolic acid and maslinic acid. The antioxidant capacity is similar for the two extracts, albeit slightly higher for OFG, possibly due to metal polyphenol complexes with antioxidant activity. The extracts elicited an antimicrobial effect at higher doses, especially against Gram-positive bacteria, such as Streptococcus pyogenes. The extract with lower inorganic content and higher content of polyphenols and triterpenic acids induced a strong anti-radical capacity, a selective cytotoxic effect, as well as antimigratory potential on A375 melanoma cells and antiangiogenic potential on the CAM. No irritability and a good tolerability were noted after evaluating the extracts on the in vivo Hen's Egg Test-Chorioallantoic Membrane (HET-CAM). Therefore, the present data are suggestive for the possible use of the two types of olive leaf products as high-antioxidant extracts, potentially impacting the healthcare system through their use as antimicrobial agents and as anticancer and anti-invasion treatments for melanoma.

Novel Anti-tumor Strategy for Breast Cancer: Synergistic Role of Oleuropein with Paclitaxel Therapeutic in MCF-7 Cells

BACKGROUND

The side effects of conventional therapeutics pose a problem for cancer treatment. Recently, combination treatments with natural compounds have attracted attention regarding limiting the side effects of treatment. Oleuropein is a natural polyphenol in olives that has antioxidant and anticancer effects.

OBJECTIVES

This study aimed to investigate the oxidative stress effect of a combination of Paclitaxel, a chemotherapeutic agent, and Oleuropein in the MCF-7 cell line.

METHODS

The xCELLigence RTCA method was used to determine the cytotoxic effects of Oleuropein and Paclitaxel in the MCF-7 cell line. The Total Oxidant and Total Antioxidant Status were analyzed using a kit. The Oxidative Stress Index was calculated by measuring Total Oxidant and Total Antioxidant states. The levels of superoxide dismutase, reduced glutathione and malondialdehyde, which are oxidative stress markers, were also measured by ELISA assay kit.

RESULTS

As a result of the measurement, IC50 doses of Oleuropein and Paclitaxel were determined as 230 μM and 7.5 μM, respectively. Different percentages of combination ratios were generated from the obtained IC50 values. The effect of oxidative stress was investigated at the combination rates of 10%, 20%, 30%, and 40% which were determined to be synergistic. In terms of the combined use of Oleuropein and Paclitaxel on oxidative stress, antioxidant defense increased, and Oxidative Stress Index levels decreased.

CONCLUSION

These findings demonstrate that the doses administered to the Oleuropein+Paclitaxel combination group were lower than those administered to groups using one agent alone (e.g. Paclitaxel), the results of which reduce the possibility of administering toxic doses.

A Comprehensive Review on the Anti-Cancer Effects of Oleuropein

In Mediterranean cuisine and culture, olive oil and olive fruits play a significant role. Many people believe that those who consume olive oil and its fruit live longer and have a decreased risk of illness. Olive leaves were used to treat a range of diseases in ancient times, including malaria fever and lower earaches. Although it was not understood at the time what key components were responsible for these effects because they had not yet been discovered, Oleuropein is now recognized as one of the primary elements in immature olive fruits and leaves. Later research was carried out to determine the effects of this molecule, and it was determined that it functions as an antioxidant. Oleuropein consumption has aided in cancer treatment over the years, and this was assumed to be owing to its antioxidant properties. Oleuropein’s effects on cancer, however, go beyond that; it is now known that Oleuropein functions as both an anti-proliferative and an apoptotic promoter in many cancer cells. The kinetics and dosages of Oleuropein and the mechanisms behind its involvement and effects in cancer are explored in this review. Finally, the effects of Oleuropein in combination with anticancer medicines are investigated.

Pro-Angiogenic Effects of Natural Antioxidants Extracted from Mango Leaf, Olive Leaf and Red Grape Pomace over Endothelial Colony-Forming Cells

Cardiovascular diseases remain the leading cause of death worldwide, mainly triggered by the formation of atherosclerotic plaques that reduce blood flow. Angiogenic cell therapy based on endothelial colony forming cells (ECFCs) constitutes a promising alternative to promote vascular revascularization; however, under the oxidative environment that prevails in ischemic areas, these cells become impaired. Thus, it is necessary to investigate strategies to enhance their regenerative properties. Antioxidant substances, such as polyphenols, have been shown to be useful for this purpose. In the current study we evaluated the potential of mango leaves, olive leaves and red grape pomace extracts, rich in polyphenols, to promote ECFC reparative effects. For this, aqueous and ethanolic extracts of the aforementioned raw materials were obtained by pressurized liquid extraction (PLE). After evaluating the polyphenol content and the antioxidant activity, in vitro assays were carried out, and we found that ethanolic extracts at low concentrations improved angiogenic capacities of ECFCs and reduced proliferation, apoptosis, and the inflammatory response of these cells. Overall, mango leaves ethanolic extract provided the most promising results, but all three extracts ameliorated the functionality of ECFCs.

The Anti-cancer Effect of Olea europaea L. Products: a Review

PURPOSE OF REVIEW

The olive tree (Olea europaea L.) has featured as a significant part of medicinal history, used to treat a variety of ailments within folk medicine. The Mediterranean diet, which is rich in olive products, is testament to Olea europaeas positive effects on health, associated with reduced incidences of cancer and cardiovascular disease. This review aims to summarise the current literature regarding the therapeutic potential of Olea europaea products in cancer, detailing the possible compounds responsible for its chemotherapeutic effects.

RECENT FINDINGS

Much of the existing research has focused on the use of cell culture models of disease, demonstrating Olea europaea extracts, and specific compounds within these extracts, have efficacy in a range of in vitro and in vivo cancer models. The source of Olea europaeas cytotoxicity is yet to be fully defined; however, compounds such as oleuropein and verbascoside have independent cytotoxic effects on animal models of cancer. Initial results from animal models are promising but need to be translated to a clinical setting. Treatments utilising these compounds are likely to be well tolerated and represent a promising direction for future research.

Aloe vera and Honey Solution and Their Ethanolic Extraction Solution Could Act on Metastasis-Regulating Processes in Walker 256 Tumor Tissues In Vivo?

Research has shown that both Aloe vera and honey have anticancer and nutrition properties, including the inhibition of metastasis. In order to evaluate the effect of a solution of Aloe vera and honey (A) and their ethanolic fraction (F) on metastasis-regulating processes in primary tumors, Wistar rats were subcutaneously implanted with Walker 256 tumors and treated with A and F (670 µl/kg by gavage, daily for 21 days). An analysis of the primary tumor tissues of these animals showed a decrease in N-cadherin expression in groups WA and WF, with a concomitant increase in E-cadherin expression in group WA compared to the control group. Cathepsin D activity was also decreased in the tumor tissues from groups WA and WF. In addition, the number of blood vessels and their diameter significantly reduced in tumor tissues from groups WA and WF compared to those from control group. UHPLC-ESI-MS/MS analysis of the samples A and F, suggested presence of molecules with verified antitumor activity, including caffeic acid, ferulic acid, mannose, aloin A, aloin B, pinocembrin, chrysin, and kaempferol. These data showed that treatment with A and F could reduce the metastatic propensity of tumors by modulating neoangiogenesis and the process of epithelial-to-mesenchymal transition.

Cancer Glycolytic Dependence as a New Target of Olive Leaf Extract

Oleuropein (Ole), the main bioactive phenolic component of Olea europaea L. has recently attracted the scientific attention for its several beneficial properties, including its anticancer effects. This study is intended to investigate whether an olive leaf extract enriched in Ole (OLEO) may counteract the aerobic glycolysis exploited by tumor cells. We found that OLEO decreased melanoma cell proliferation and motility. OLEO was also able to reduce the rate of glycolysis of human melanoma cells without affecting oxidative phosphorylation. This reduction was associated with a significant decrease of glucose transporter-1, protein kinase isoform M2 and monocarboxylate transporter-4 expression, possible drivers of such glycolysis inhibition. Extending the study to other tumor histotypes, we observed that the metabolic effects of OLEO are not confined to melanoma, but also confirmed in colon carcinoma, breast cancer and chronic myeloid leukemia. In conclusion, OLEO represents a natural product effective in reducing the glycolytic metabolism of different tumor types, revealing an extended metabolic inhibitory activity that may be well suited in a complementary anti-cancer therapy.