Frost decreases content of sugars, ascorbic acid and some quercetin glycosides but stimulates selected carotenes in Rosa canina hips created by Vlasta Cunja, Maja Mikulic-Petkovsek, Anka Zupan, Franci Stampar and Valentina Schmitzer

Primary and secondary metabolites of Rosa canina hips were determined by HPLC/MS during ripening and after frost damage. Rose hips were harvested six times from the beginning of September until the beginning of December. Color parameters a*, b* and L* decreased during maturation. Glucose and fructose were the predominant sugars representing up to 92% total sugars, and citric acid was the major organic acid detected in rose hips (constituting up to 58% total organic acids). Total sugar and ascorbic acid content significantly decreased after frost damage; from 42.2 to 25.9 g 100 g−1 DW for sugars and from 716.8 to 176.0 mg 100 g−1 DW for ascorbic acid. Conversely, β-carotene and lycopene levels increased in frostbitten rose hips to 22.1 and 113.2 mg 100 g−1 DW, respectively. In addition to cyanidin-3-glucoside (highest level in hips was 125.7 μg 100 g−1 DW), 45 different phenolic compounds have been identified. The most abundant were proanthocyanidins (their levels amounted up to 90% of total flavanol content) and their content showed no significant differences during maturation. The levels of catechin, phloridzin, flavanones and several quercetin glycosides were highest on the first three sampling dates and decreased after frost. Antioxidant capacity similarly decreased in frostbitten rose hips. Total phenolic content increased until the third sampling and decreased on later samplings.