# Biochemical Characterization of Some Plum Cultivars Available on the Romanian Market
## 1 Introduction  
The plum (_Prunus domestica_ L.) is one of the most widely grown fruit trees in temperate regions of the world. In addition to the European plum, its close relative, _Prunus salicina_ Lindl, the Japanese plum, is another widely cultured species. Most plum cultivars today derive from one or another of these two species or from hybrids (which sometimes also derive from other species, such as _P. simoniu_ or _P. crasifera_--the cherry plum). The most economically important part of the plant is, obviously, the fruit, a fleshy drupe, which has high variability in its shape, texture, flavor and biochemical properties. Plums can be small or large (with limits of variation around 2-7 cm in diameter), with smaller or larger stones. They can be oval or round, purple to blue, red, black or even green or yellow in color. The numerous varieties of European plum fruits can be classified into several major types, such as egg plums, damsons, mirabelles or greenages [1]. In Romania, as well as in all neighboring countries, plums are very popular due to their suitability to local climate and soil conditions, hardness, nutritional value and local tradition. Orchards cover around 1.4% of Romanian agricultural land [2]; in 2018, 46.90% (over 65,900 ha) of this land was occupied by plum trees, making Romania the fourth largest plum producer worldwide. The local germplasm includes numerous foreign varieties (developed in the USA, other Eastern European countries, etc. ), of which six are more common, but it also comprises a wide array of locally developed cultivars. Duringthe last six decades, over 40 Romanian varieties were developed in research centers, such as those in Bistrita, Pitesti, Strejesti, Valcea or Voinesti, and around 1000 hybrids were obtained [3; 4]. Plums have many uses; they are mostly consumed raw, but they can also be used in sweets, and they are used as ingredients in a wide assortment of jams, jellies and, through fermentation and distillation, extremely popular traditional plum brandies, such as tuica, palinca and horinca. Plum fruits are not only valued for their taste and multiple uses; they are also a source of several major classes of bioactive compounds, including key antioxidants, which are compounds that lower the impact of free radicals (especially reactive oxygen species). As such, they offer several benefits for human health, helping to fight a wide array of diseases and mitigating the effects of aging. Thus, determining the amounts of these compounds is of great interest when it comes to assessing their role in the human diet. Carotenoids are the main accessory photosynthetic pigments in plants and green organs, but they are also abundant in petals and fruit peels. Various carotenes, lycopene, lutein and xanthins are among the most important. Some carotenoids (especially \(\beta\)-carotene) are used to synthesize retinol and, indirectly, melanin in the human body; these are key compounds necessary for eye and skin functioning. Carotenoids are also important antioxidants, and some of them have strong antifumoral properties, especially lycopene [5]. While \(\beta\)-carotene is a crucial nutrient, which is a precursor to retinol and is also involved in skin protection against ultraviolet radiation, lycopene and lutein are also important to human health. Lycopene is a strong antioxidant and inhibits the growth of various tumoral cells, providing a degree of protection against lung, skin, mammary and prostate cancer. It also seems to lower the risk of preeclampsia and fetal growth problems. Lutein, on the other hand, is a key pigment in the macular area of the human retina that protects photoreceptor cells from excess radiation. Also found in the crystalline lens, it lowers the oxidative stress at this level, reducing the risk of cataract formation. Lutein uptake also seems to have protective effects against skin and colon tumors [6].