The conundrum of yellow-skinned plum (Prunus domestica L.) fruits

European plum (Prunus domestica) cultivars exhibit large variability in fruit characteristics such as shape, size, skin color, sugar content, and taste. The color of the fruit skin is an important marker for quality and ripeness. In order to clarify the differences in polyphenolic content between yellow- and purple-skinned plums, fruits of six cultivars were harvested during three consecutive years. Juices from these fruits were analyzed by reversed-phase high-performance liquid chromatography (HPLC) to identify polyphenols present in the samples. The results show that the color in the skin of purple plums is mainly determined by the presence and concentration of anthocyanins in the fruit skin (exocarp). Four anthocyanins were identified: cyanidin 3-O-rutinoside, cyanidin 3-O-glucoside, peonidin 3-0-rutinoside and peonidin 3-0-glucoside. In all purple cultivars, cyanidin 3-0-rutinoside was the most abundant anthocyanin, and peonidin 3-0-glucoside was the least abundant one.