Ultrasound-assisted Extraction of Ursolic Acid from the Flowers of Linn (Rubiaceae) and Antiproliferative Activity of Ursolic Acid and Synthesized Derivatives.

Background: Linn (Rubiaceae) is an evergreen shrub with bright scarlet colored flowers found in several tropical and subtropical countries. It is used as an ornamental and medicinal plant. Phytochemical studies revealed that its major special metabolites are triterpene acids, such as ursolic and oleanolic acid.

Objective: To evaluate the isolation of ursolic acid (UA) (1) from methanol extracts of flowers through two methodologies, to prepare four derivatives, and to evaluate the cytotoxic effect against six cancer cell lines.

Materials And Methods: The UA was isolated from vegetal material by percolation at room temperature and by ultrasound-assisted extraction. The preparation of derivatives was performed according to literature methods, and the cytotoxic effects were evaluated using the MTT (3,4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide) assay.

Results: The most efficient extraction was achieved through ultrasound irradiation with a yield of 35% after KOH-impregnated silica in chromatography column. Furthermore, four derivatives (3, 5, 6, 7) of UA were prepared and evaluated, including 1, against two lung cancer (A549 and H460) and four leukemia (K562, Lucena, HL60, and Jurkat) cell lines. Generally, results showed that 1 and 7 were the most active compounds against the assayed cell lines. Also, the cytotoxic effects observed on terpenes 1 and 7 were higher when compared with cisplatin, used as positive control, with the exception of Jurkat cell line.

Conclusion: The efficiency of such an alternative extraction method led to the principal and abundant active component, 1, of , thus representing a considerable contribution for promising triterpenoid in cancer chemotherapy.

Summary: The ultrasound-assisted extraction of flowers improved of the ursolic acid isolationMethanolic extract from flowers of provided, by ultrasound irradiation, after KOH-impregnated silica in chromatography column, the ursolic acid in 35% yieldThe ursolic acid and four derivatives were prepared and assayed against two lung cancer and four leukaemia cell linesThe ursolic acid and their 3-oxo-derivative, in general, were more cytotoxic when compared to cisplatin, used as positive control MTT: 3,4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide, RP: reverse phase, TLC: thin layer chromatography, KOH: potassium hydroxide, IR: infrared, DMF: dimethylformamide, DMSO: dimethyl sulfoxide, TEA: triethylamine, RT: room temperature, EtOAc: ethyl acetate, MeOH: methanol, -PrOH: -propanol, NMR: nuclear magnetic resonance, MDR: multiple drug resistance, RPMI: Roswell Park Memorial Institute.