Phenolic compounds in native potato (Solanum tuberosum L.) cooking water, with potential antioxidant activity

On that area, hunter-gatherer communities that had inhabited the southern part of the continent for at least 7000 years began to domesticate wild potato plants, growing in abundance around the lake, which they used as food and medicine. Potato is currently the fourth most important crop in the world for its high yield and nutritional value; it is an excellent source of carbohydrates, proteins, vitamins and minerals and is a rich source of antioxidants (Buono et al., 2009; Ezekiel et al., 2013). For two decades, there has been an increasing interest in finding natural antioxidants, because they can protect the human body from free radicals and slow down the progress of many chronic diseases (Kinsella et al., 1993). Ot has been demonstrated in vivo that the phenolic compounds of the potato are substances that have antioxidant, antiproliferative and anticancer properties (Han et al., 2007; Thompson et al., 2009) and the benefits for human health have also been tested in vitro (Madiwale et al., 2011; Ji et al., 2012), for their anti-inflammatory, analgesic, antimicrobial, neuroprotective, and cardioprotective action (Dng et al., 2013; André et al., 2014) and its antihyperglycemic effect (Singh & Rajini, 2005). Chlorogenic acid was investigated for its protective effects on glutamate-induced neuronal cell death because the release of glutamate during brain ischemia triggers the death of neurons and prevents the increase of intracellular concentrations of Ca2+ caused by the addition of glutamate (Mikami & Yamazawa, 2015). Studies have also shown that it is a phenolic compound that exerts anti-inflammatory and antioxidant activities; results suggest that chlorogenic acid protects against induced liver fibrosis, at least in part, through the suppression of oxidative stress in liver and hepatic stellate cells (Shi et al., 2016). Dn the other hand, caffeic acid has been studied in cervical cancer cell lines (HeLa cancer cells) and found to have significant antiproliferative effects on this type of cell (Markovic & Tosovic, 2016; Ye et al., 2010). Another study shows that when caffeic acid was applied to hair cells at doses of 10 or 50 mg/mL, they exhibited free radical scavenging Phenolic compounds in native potato (Solanum tuberosum L.) cooking water, with potential antioxidant activity


OBJECTIVE
Identify and quantify phenolic compounds found in potato cooking water to demonstrate that it contains bioactive antioxidant compounds with a potentially beneficial effect on human health.

Plant materials
Fields trials were carried out in Santiago de Chuco -La Libertad at two experimental sites: El Zuro (EZ) and Huayatan Alto (HA). Potatoes from EZ and HA were classified in two samples : a. Whole fresh potatoes were washed with tap water and the surface allowed to dry, manually cut into slices of 5 mm thickness, freeze-dried and packaged with liquid nitrogen in sealed jars. These samples will be called throughout the article as SP-EZ and SP-HA.
b. Whole potatoes were stored as raw material at 18.5 -21.5 °C, 68 -70% Relative Humidity for 20 days. These samples will be called throughout the articles as RP-EZ and RP-HA.

Sample preparation
The following treatments were used prior to extraction: a. SP-EZ and SP-HA were unfreezed and then boiled in water 1/3 w/w (slices / water) for 20 min from boiling point. We analyzed phenolic compounds in SP water.
b. RP-EZ and RP-HA were boiled in water 1/3 w/w (potato/ water) for 20 min from start point. We analyzed phenolic compounds in RP water.

Extraction
Extraction solution (ES) used was an aqueous solution of 50% methanol (HPLC grade-Sigma Aldrich) and 0.5% acetic acid (Fluka Analytical HPLC-grade), the same ES used by Narváez-Cuenca et al., (2012). An aliquot solution of boiling water of each two treatment (SP and RP) was After centrifugation (Eppendorf 5424, Germany) at 15000 g for 10 minutes at 4°C, 350 μL of the supernatant was removed and put in a new tube. The process was repeated two more times with the resultant pellet, and the supernatants were pooled together. A final centrifugation (Eppendorf 5424, Germany) at 20000 g for 10 min at 4°C was performed to remove any remaining tissue suspension, and stored at -80°C until further analysis. Each treatment was repeated three times.   10). The first eight were scanned in positive mode and the last in negative mode. A calibration curve (0.1 ng a 100μg) using the respective standards of each metabolite was generated to determine the absolute quantification. The generated data were analyzed in the software "MassHunter Workstation" VB 06.00, which obtained the peak areas for each phenolic metabolite and the results were expressed in mg/100 g of dry tissue.

Statistical analysis
Principal Components Analysis (PCA) was performed using Software XLSTAT 2015 (Digital license).

RESULTS
In Figure 1   According to the World Health Report (WORLD HEALTH ORGANIZATION, 2002), low fruit and vegetable consumption reflects the population´s economic, cultural, and agricultural environment. It has become one of the ten main risk factors attributed to mortality from non-communicable diseases. It depends on whether many people with low consumption of fruit and vegetables result in approximately 19% of gastrointestinal cancers, 31% of ischemic heart disease, and 11% of cerebrovascular accidents. In total, 2.7 million deaths (4.9%) and 26.7 million lost years of healthy life (1.8%) were attributed to the low consumption of fruit and vegetables.  For the results in this research, potato cooking water could be considered as a nutraceutical food. This potato water is traditional medicine in the Peruvian Andes for illness and wellness purposes in humans. However, further research is required to identify any other substances harmful to health, depending on the amount consumed. The thirteen metabolites found in potato cooking water are the same as those found in raw potatoes of the same variety and origin (ROJAS -PADILLA & VÁSQUEZ VILLALOBOS, 2016).

CONCLUSION
The cooking water of the Huagalina native potato SP-EZ and SP-HA contains phytonutrients with potential antioxidant activity to prevent non-transmissible degenerative diseases.
The phenolic compounds with the higher concentrations were (mg/100 g freeze-dried SP): Chlorogenic acid (46.18), vanillin (16.03), p-coumaric acid (9.73), caffeic acid (9.41), coumarin It is vital to continue studying the environmental conditions of potato cultivation, which are responsible for the different distribution of the phenolic compounds in both locations studied, highlighting the predominance of the genetics of the Huagalina variety in the profile of the phytonutrients found. Potato cooking water could be considered a nutraceutical food.
However, further research is required to identify any other substances harmful to health, depending on the amount consumed.