Extraction of ursolic acid from Ocimum sanctum and synthesis of its novel derivatives: effects on extracellular homocysteine, dihydrofolate reductase activity and proliferation of HepG2 human hepatoma cells

Abstract

Abstract The objective of the present study was to extract ursolic acid (UA) from Ocimum sanctum, to synthesize its bioactive derivatives, evaluate the anti-cancer effect of its derivatives and to establish the possible mechanism of action. In the present report, we extracted UA from whole plant of O. sanctum, synthesized its novel derivatives and investigated their effect on homocysteine metabolism and dihydrofolate reductase (DHFR) activity of HepG2 cells. UA and its derivatives UA-1, UA-2 and UA-3 down-regulated DHFR activity and increased extracellular homocysteine. UA-2 showed significant anti-proliferation activity in cancer cells. Cancer cells have increased the requirement of pyrimidine base thymidylate due to rapid cell division. Thymidylate biosynthesis depends on sufficient pools of folate dependent enzymes like DHFR. In the present study, we examined the UA and its derivatives mediated perturbation of DHFR activity and extracellular homocysteine in HepG2 human hepatoma cells. After incubation with UA-2, a potent inhibition of DHFR activity was observed. Our results showed that derivatization of UA might adversely affect DHFR activity. Measurement of extracellular homocysteine indicated impaired one-carbon metabolism in cells treated with UA derivatives. In conclusion, our data suggest an anti-cancer role of UA and its derivatives via inhibition of one-carbon metabolism.