# Biochemical Characterization of Some Plum Cultivars Available on the Romanian Market
## 1 Introduction
Phenolic compounds are an even more diverse compound class, which includes flavonoids (such as flavanols, flavones, isoflavones and anthocyanins), phenolic acids, stilbenes, tannins and coumarins. They are important chemical components in fruits, as anthocyanins are involved in fruit skin pigmentation. For plants, they fulfill various protective roles; meanwhile, for consumers, phenolic compounds are the main class of antioxidant, free radical-scavenging agents helping to fight infection, control the immune response, sustain cardiovascular health, mitigate the effects of aging, etc., while often easing digestive processes and improving the uptake of other valuable nutrients [7; 8]. Among phenols, flavonoids are some of the strongest dietary antioxidants. Due to their active hydroxyl groups, they are able to quench free radicals (although glycosylation, common in fruit tissues, somewhat lowers their efficiency). These compounds are of interest mostly due to the correlation between high dietary uptake and enhanced protection from cardiovascular diseases and tumors. Among them, flavanols or catechins are also known for their antiviral properties and modulation of gut-microbial interactions. They include compounds like catechin, epicatechin, epicatechin gallate, epigallocatechin or epigallocatechin gallate, which are found in a wide variety of food products, including fruits. Anthocyanins (including compounds like cyanidin, delphinidin, malvidin, pelargonidin, etc.) are known to lower the risk of inflammation, cardiovascular diseases, obesity and cancer. Some of them, like cyanidin (one of the major anthocyanins in plum fruits), were found to help maintain the functionality of chondrocytes and, along with malvidin, the proper functioning of monocytes [9; 10; 11]. Hydroxygenozoic acids include compounds such as protocatechic acids, vanillic acids, syringgic acid, p-hydroxybenzoic and gallic acid. While usually less effective antioxidants than their hydroxycinnamic counterparts, they are still highly beneficial in radical scavenging. Hydroxycinnamic acids, on the other hand, include compounds such as caffeic, ferulic, p-coumaric and p-hydroxycinnamic acids. One of the most important health benefits of both types of phenolic acids is reduced inflammation. Studies performed on rats showed a mitigation of inflammation in ulcerative colitis, for instance. Another important function is increasing the diversity of gut microbiota, which leads to anti-diarrheal effects. Several of these compounds, including caffeic acid, have been found to exhibit cardioprotective properties and to lower the risk of hypertension. Antitumoral, anti-hyperglycemic, neuroprotective and antidepressant properties are also known for this class of compounds. Gallic acid was found to lower cognitive decline in mice [9; 10; 11]. Among stilbenes, resveratrol is the most well-known and the most common, mostly occurring in fruit skins. Its main role in plant tissues (including fruits) seems to be protection against fungal infections, ultraviolet radiation damage and lesions. For human consumers, it is known for its anti-inflammatory, antiviral and antitumoral properties. It also lowers the risk of thrombosis and other cardiovascular diseases and protects the nerve system. For these reasons, it is considered among the most important anti-aging nutrients while also helping mitigate the cardiovascular effect of a lipid-rich diet (especially with a constant intake of saturated fatty acids) [10]. Tannins, on the other hand, have rather mixed health effects. While also an antioxidant, they are significantly less effective than flavonoids, for instance. Yet, some of them may compensate for this through polymerization. In both condensed and hydrolysable tannins with high molecular masses, the antioxidant activity can surpass that of simple phenolic compounds such as phenolic acids by 15-30 times. The high antioxidant potential of such polymers is limited by their low uptake through the intestinal mucosa.