Honey locust (Gleditsia triacanthos) flowers and its bioactive constituents

Honey locust, Gleditsia triacanthos L. (Fabaceae), is one of the popular deciduous trees native to central North America. Its leaves and seeds have been used in traditional food and medicine by Native Americans. Extracts of Gleditsia spp. have been reported to possess medicinal properties and used in treating rheumatoid arthritis, cancer and a variety of other illnesses. Phytochemical studies on its leaves and seeds have reported the presence of triterpenoids, alkaloids, flavonoids, galactomannans and tannins. However, there are no reports on its flowers for the presence of bioactive constituents. In our study, the hexane, ethyl acetate and methanolic extracts of the flowers of honey locust tree showed antioxidant, antiinflammatory and antitumor activities. Purification of these active extracts yielded 4 new compounds, together with 15 known compounds. Their structures were elucidated by spectral analyses. All pure isolates inhibited lipid peroxidation (LPO) by 20 – 94%, and cyclooxygenase enzymes, COX-1 by 35 – 55% and COX-2 by 23 –38% at 25 µg/mL. The tumor cell proliferation inhibitory activity of these compounds was determined agianst AGS (gastric), DU-145 and LNCaP (prostate), HCT-116 (colon), MCF-7 (breast), and NCI-H460 (lung) human tumor cell lines. All isolates tested at 25 µg/mL showed some degree of inhibition against tumor cell progression.