BACKGROUND: Strawberries are consumed worldwide. In Chile, strawberry production has been established in Andisols, were phosphorus is scarce. Traditional fertilization (TF) and organic fertilization (OF) have both been established there. This study examined their impact on the polyphenolic content of strawberries. RESULTS: Two anthocyanins were identified by high performance liquid chromatography with diode array detection coupled to mass spectrometry (HPLC-DAD-ESI-MS/MS). The average total anthocyanin concentrations were found to be 651 mg kg −1 fresh weight in 100% OF, which represents a 56% increase compared to fruits that were not fertilized. In the case of flavonols, only quercetin-rhamnoside was identified, and its concentration reached 14.6 mg kg −1 with 100% OF. The ascorbic acid concentration reached 0.54 g kg −1 in 50% TF (a 20% increase over fruits without fertilization, WF). The antioxidant activities slightly increased in the fruits subjected to TF and OF in comparison with WF treatment. CONCLUSION: These results support a management strategy for obtaining the best quality and potential beneficial effects in health by increasing anthocyanins and other polyphenols under OF.
ReagentsThe commercial standard of pelargonidin-3-glucoside chloride (98.95%) was obtained from Phytolab (Vestenbergsgreuth, Germany). Quercetin (> 95%) and ascorbic acid (99.7%) was acquired from Sigma-Aldrich (Steinheim, Germany). The standards of TROLOX (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxilic acid), ABTS (2,2 ′ -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)), gallic acid and sodium carbonate were obtained from Sigma-Aldrich. HPLC grade solvents as water, methanol, acetonitrile and p.a. grade as formic acid, ammoniac, and hydrochloric acid were acquired from Merck (Darmstandt, Germany).
Identification and quantification of anthocyanins and flavonolsHigh performance liquid chromatography with diode array detection coupled to mass spectrometry (HPLC-DAD-ESI-MS/MS) analyses of anthocyanins were carried out using a Shimadzu HPLC system (Tokyo, Japan) equipped with a quaternary LC-20AT pump with a DGU-20A5R degassed unit, a CTO-20A oven, an SIL-20a autosampler, and a UV-vis diode array spectrophotometer (SPD-M20A). The compounds were identified by a HPLC-DAD system coupled to a mass spectrometer (QTrap LC/MS/MS 3200 Applied Biosystem MDS Sciex system (Foster City, CA, USA)). The instrument was controlled and data were collected using Analyst J Sci Food Agric 2019; 99: 2404-2410