2.4.1. Freezing procedure
About 100 g of each maturity stages (fully ripe, half-ripe, and unripe) of dog rose and orange samples were separately frozen into liquid nitrogen and stored at −70 °C until the analysis were carried out. Frozen pulverized samples were weighed (1.0 g for orange, 1.0 g for fully ripe, 1.0 g for half-ripe, and 2.0 g for unripe dog rose sample) and mixed with 5 mL of the extractant solution containing 5% of MPA. The mixture was homogenized for 5 min and then it was centrifuged at 2000 rpm for 10 min. All extractions were carried out under reduced light and at 4 °C. All the extraction processes was three times replicated. The extracts were stored at 4 °C less than 1 h before analysis. Dog rose extracts were diluted 5 times with HPLC-grade water and subsequently were injected. The injection of extracts into HPLC system was performed twice