Title : Phytoconstituents of the aromatic plants hop and stevia present antiproliferative activity on cancer cells: A systematic review and meta-analysis
Stevia rebaudiana and hop (Humulus lupulus) are aromatic plants of great importance in agrifood-sector industry, i.e., stevia for its almost zero calorie sweetening power, and hop for the plethora of aromas, tastes, and colours that confers to beer. These two aromatic plants are currently extensively investigated for their medicinal potential. Emerging research and evidence suggest that stevia contains various other compounds with biological activities such as antidiabetic, anticarcinogenic, antihypertensive, antimicrobial or antioxidant. Likewise, phytoconstituents of hop female cones include polyphenols and α- and b-acids that also grant health promoting properties (anticancer, antimicrobial, antioxidant). In the present study a systematic review was performed to evaluate growth inhibition of cancerous cell lines by either pure phytoconstituents found in stevia and hop or by extracts from stevia leaves and hop-cones. Concerning stevia, systematic literature search returned 64 studies from which 7 fulfilled eligibility criteria for meta-analysis and provided data on 40 different studies for 5 cancer types. From 622 articles retrieved from literature search concerning hop, only 55 containing 451 studies for 25 cancer types fulfilled inclusion criteria to be subjected to meta-analysis. As effect estimate the half maximal inhibitory concentration (IC50) was recorded, along with standard deviation. Data on MTT assays were given for stevia compounds and extracts while SRB and Crystal Violet (CV) assays data were also available for hop. Meta-analysis and meta-regression based panoramic meta-analysis was performed, using STATA 13.1 software. Antiproliferative effects were analysed for each method, across studies, for each compound or extract, and cancer type for various time points. Our results on stevia biocompounds suggest that they exert an overall inhibitory effect (48 hours) with IC50: 152.5μg/ml which is mostly attributed to stevia phenolic compounds (IC50 86.0μg/ml) and not to glycosides (IC50: 229.7μg/ml) or diterpenes (IC50: 167.3μg/ml). Moreover, a very high inhibitory activity is observed on neuronal cells (IC50 21.0μg/ml) compared to other cancer types, e.g., gastrointestinal cancers (IC50: 162.6μg/ml). Meta-analysis on hop derived compounds assays data showed that flavonoids exert a remarkable antiproliferative effect on cell growth of cancerous cell lines which is mainly due to Xanthohumol (48 hours treatment, IC50 of flavonoids: 30.8μM, IC50 of Xanthohumol: 17.9 μM). Importantly, bitter acids show even stronger antiproliferative activity with IC50: 8.2μM. Meta-regression revealed that the results from SRB, MTT and CV methods did not statistically significantly differ (p-value<0.05) and can be used interchangeably. Importantly, every compound either from stevia or from hop exerted higher anti-proliferative effect on cancerous cells compared to normal cells. Our study provides the basis for quantitative estimations of health promoting properties of stevia and hop plants that can guide further investigations to produce novel nutraceuticals.
What will audience learn from your presentation?
- Stevia and hop phytoconstituents possess antiproliferative activity on cancerous cell lines.
- Polyphenols from stevia exert the highest antiproliferative activity.
- Bitter acids from hop are even more potent than polyphenols antiproliferative agents.
- SRB, MTT and CV methods did not statistically significantly differ (p-value<0.05) and can be used interchangeably.
- This study, using the robust methodology approach of meta-analysis, provides the basis for quantitative and statistically significant estimations of health promoting properties of stevia and hop plants.