Comparison of flavonoid composition of red raspberries ( Rubus idaeus L.) grown in the southern United States.

Raspberry flavonoid compounds have significant antioxidant activities, and regular consumption may help prevent and/or moderate chronic diseases. Targeted metabolite profiling is useful to identify compounds contributing to these antioxidant properties and health benefits and for tailored breeding for functional foods. In this study, metabolomic variation was determined among three fall-fruiting red raspberry cultivars ('Autumn Britten', 'Caroline', 'Nantahala') grown at three North Carolina locations differing in elevation and average day/night temperatures. 'Nantahala' was specifically bred for the mountainous regions of the southern United States. Ten flavonoid compounds were detected by liquid chromatography-time-of-flight-mass spectrometry (LC-TOF-MS). Of those, cyanidin-3-glucoside, cyanidin-3-sophoroside, cyanidin-3-rutinoside, cyanidin-3-sambubioside, and quercetin-3-glucoside were quantified against external standards. Variation in flavonoid composition was primarily attributed to genotype and associated with night temperature and hours exposed to temperatures over 29 °C. 'Nantahala' had particularly high levels of cyanidin-3-sambubioside, indicative of its purple raspberry lineage. Quercetin-3-glucoside levels increased the most with elevated temperatures.