Anti-inflammatory Properties of Citrus Limonoids and Their Isolation and Characterization

This dissertation investigates the role of limonoids in inflammation to reduce risk of breast cancer and cardiovascular disease. Radical scavenging activity and apoptotic effects of extracts from lemon seeds were investigated in human breast adenocarcinoma (MCF-7) cells and non-malignant breast (MCF-12F) cells. The MeOH:water (80:20) extract showed the highest (29.1%, P < 0.01) inhibition of MCF-7 cells without affecting the non-malignant breast cells. Further, the purified and modified limonoids were screened for their cytotoxicity on estrogen receptor (ER)-positive (MCF-7) or ER-negative (MDA-MB-231) human breast cancer cells. The MCF-7 cell was more susceptible to tested limonoids. Although most of limonoids induced anti-aromatase activity, the inhibition of proliferation was not related to the anti-aromatase activity. On the other hand, the anti-proliferative activity was significantly correlated with the level of caspase-7 activation by limonoids. The next study investigated the mechanism of anti-breast cancer and anti-aromatase activities of obacunone through inhibition of MCF-7 cell proliferation without affecting non-malignant breast cells. Treatment with obacunone resulted in an increased G1 cell cycle arrest and induction of apoptosis. Exposure of MCF-7 breast cancer cells to obacunone down-regulated expression of inflammatory molecules including nuclear factor-kappa B (NF--2 (COX-2). Furthermore, potential of obacunone on inhibition of COX-2 and NF-the p38 mitogen-activated protein (MAP) kinase was also investigated. In the final study, nomilin was the most potent natural inhibitor for p38 MAP kinase activity in human aortic smooth muscle cells indicating that a seven-membered A ring with acetoxy group, present in nomilin, seems to be essential for its inhibitory activity on p38 MAP kinase. The possible mechanism of nomilin for prevention of cardiovascular disease was determined. Pre-treatment with nomilin resulted in significant inhibition of TNF- induced HASMCs proliferation. The anti-proliferative activity of nomilin is due to apoptosis through mitochondrial dependent pathway