Isolation and characterization of 3- O-caffeoyloleanolic acid from Robinia pseudoacacia stem bark

Robinia pseudoacacia , a deciduous tree native to North America, has various medicinal properties, including antioxidant, antitumour, diuretic and antispasmodic effects. The plant contains various bioactive compounds, such as alkaloids, flavonoids, tannins, and phenols. However, caution is advised as all parts of the plant, except the flowers, are poisonous due to the phytotoxin robinin and its glycoside. The bark, on the other hand, shows resistance to rot due to the antifungal compounds dihydrorobinetin and robinetin. This study focuses on the stem bark of R. pseudoacacia from Bulgaria, a widely distributed wild species. Using advanced chromatographic techniques, we isolated and identified 3- O -caffeoyloleanolic acid, a new compound in the genus Robinia and R. pseudoacacia . Structural characterization was performed by state-of-the-art spectroscopic methods, including 1 H NMR, 13 C NMR and 2D NMR (COSY, HSQC, HMBC), as well as by LC-HRESI-MS analysis.