Although a number of chemicals have been isolated from Terminalia arjuna, only a few have been evaluated for their biological significance. As a part of our drug discovery programme for cytotoxic agents from Indian medicinal plants, four novel cytotoxic agents arjunic acid (1), arjungenin (2), arjunetin (3) and arjunoglucoside I (4) were isolated from the bark of T. ARJUNA. Out of the four compounds, arjunic acid (1) was significantly active against the human oral (KB), ovarian (PA 1) and liver (HepG-2 & WRL-68) cancer cell lines. Further, the most active compound arjunic acid was converted into seven semi-synthetic ester derivatives 5 - 11. 2-O-Palmitoyl arjunic acid (6) showed two times more activity, while 2, 3-di-O-acetyl-, 2-O-p-anisoyl-, 2, 3-di-O-benzoyl- and 2, 3-di-O-p-nitrobenzoyl arjunic acid (7 - 10) showed 1.7 - 2.3 times less activity than the cytotoxic drug vinblastine against the liver cancer cell lines HepG-2 and WRL-68 respectively.

Detailed chemical investigation of Withania somnifera roots resulted in the isolation and identification of a cytotoxic and hepatoprotective agent, palmitic acid (1), which was converted to eight semi-synthetic ester derivatives 2-9. t-Butyl palmitate (8) and amyl palmitate (9) were 4-6 times more active than 1 against adherent and suspension colon cancer cell lines. Interestingly, palmitic acid (1) and its ester derivatives 2-9 also showed hepatoprotective activity which is being reported for the first time.

Detailed chemical investigation of Terminalia arjuna bark resulted in the isolation and identification of an immunomodulatory constituent, arjunic acid (1), which was converted into seven semi-synthetic derivatives (2-8). All the test compounds in 0.1, 1 and 10 µg/mL concentrations exhibited immunomodulatory effects in a dose dependant manner. 2-O-Lauroyl arjunic acid (3) and 2-O-palmitoyl arjunic acid (4) exhibited immunostimulatory response at all the tested concentrations, while arjunic acid (1), 2,3-di-O-acetyl arjunic acid (2), 2,3-di-O-benzoyl arjunic acid (6), and 2-O-p-anisoyl arjunic acid (7) exhibited immunostimulatory responses at lower doses, whereas at higher concentrations they exhibited immunosuppressive activity. Only 2,3-di-O-palmitoyl arjunic acid (5) showed immunosuppressive activity at all the concentrations; this is being reported for the first time.

Although a number of chemicals have been isolated from Lantana camara, only a few have been evaluated for their biological significance. As part of our drug discovery program for cytotoxic agents from Indian medicinal plants, roots of L. camara L. were chemically investigated, which resulted in the isolation and identification of a cytotoxic agent, oleanolic acid (1b) as a major constituent. Oleanolic acid was converted into six semi-synthetic ester (2-7) and seven amide (8-14) derivatives. The ester derivatives (2-7) showed 3-6 times more selective activity than 1b against the human ovarian cancer cell line (IGR-OV-1), while amide derivatives 8-14 showed 16-53 times more selective activity against the human lung cancer cell line (HOP-62). Structure activity relationship within the ester (2-7) and amide (8-14) derivatives are discussed.