Lipid Peroxidation, Cyclooxygenase Enzyme and Tumor Cell Proliferation Inhibitory Lignans from Justicia Species

The genus Justicia is a rich source of lignans, especially aryl naphthalide lignans. Lignans are biologically active phytochemicals, and are reported to possess antiplatelet, antiviral, anti-tumor, antidepressant, and insect antifeedant activities. In the present study, we report lipid peroxidation (LPO), cyclooxygenase (COX-1 and −2) enzyme and tumor cell proliferation inhibitory activities of lignans, namely, lariciresinol (1), isolariciresinol (2), neesiinoside A (3), justirumalin (4), justalakonin (5), justicidin G (6), sesamin (7), sesamolin (8), jusmicranthin methyl ether (9), taiwanin E methyl ether (10), lignan J1 (11), jusneesiinol (12), jusmicranthin ethyl ether (13), tiruneesiin (14), justicidin E (15) and simplexolin (16). Lignans 1 and 2 were isolated from J. tranquebariensis, 3, 4, 6, 9, 10, 11, 12, 13 and 14 from J. neesii Ramamoorthy, 5 from J. purpurea and 7, 8, 15 and 16 from J. orbiculata. Among the lignans assayed, 1, 2, 12 and 14 showed 79.6, 86.2, 90.8 and 95.9% and 3 41.3% inhibition of LPO at 25 μg/mL. The lignans 4, 9 and 16 inhibited COX-2 enzyme by 67.2, 73.0 and 72.8%, respectively, when tested at 25 μg/mL. Similarly, lignans 3, 4, 10, 11 and 15 inhibited COX-1 enzyme by 59.9, 89.2, 69.6, 73.9, and 80.1%, respectively, at 25 μg/mL. When assayed at 25 μg/mL, 4 inhibited human stomach and breast cancer cell lines by 42.8 and 42.1%, respectively. Also, at 25 μg/mL the lignan 7 inhibited the growth of CNS, lung and breast cancer cell lines by 50.0, 41.3, and 42.0 %, respectively, and 15 inhibited the proliferation of lung, breast and colon cell lines by 40–53%.