Investigation of chemopreventive foods and herbs: I. Isolation and identification of cytotoxic compounds from bay leaf (Laurus nobilis). II. Identification and quantification of sphingolipids in nuts and seeds.

摘要

Cancer is one of the major causes of death in the United States, human epidemiology and animal studies have indicted that cancer risk may be modified by dietary components. One of the important mechanisms involved in cancer prevention and cancer therapy is apoptosis. Isolation and identification of apoptosis inducing compounds in dietary components is the purpose of this study.;Bay leaf belongs to the family Lauraceae, and is one of the most popular culinary spices. Bay leaf has been used as herbal medicine and has many pharmacological activities include anti-bacterial, anti-fungal, anti-diabetes and anti-inflammatory effects, but few studies were carried out about its anti-tumor effect. The goal of this study is to identify compounds from Laurus nobilis, which are responsible for inducing apoptosis using bioassay-directed isolation. The isolation of active compounds was carried out in three steps: multiple extractions, fractionation using column chromatograph and purification using semi-preparative HPLC. The structure of separated compounds was determined on the basis of 1H, 13C NMR, ApCI/MS, EI/MS data and comparing with the literature. Six compounds were identified; all of them are sesquiterpene lactones.;Studies with experimental animals showed that dietary sphingolipids significantly reduced early stage colon carcinogenesis and tumor formation, but knowledge about the amount and structure of sphingolipids in foods, especially plant-derived foods is sparse due to lack of effective identification and quantification methods. Also it is critical to know the structure of sphingolipids to understand the potential link between diet and cancer. In this study, a LC/MS method was developed to separate and identify ceramide and cerebroside species simultaneously in plant samples and ten plant samples were screened for the ceramide and cerebroside content. The ceramides found in the samples contain mainly trihydroxy bases. Both nonhydroxy and alpha-hydroxy fatty acids were found, and they are mostly very long chain fatty acids (C > 20). Cerebrosides of the plant samples have both dihydroxy and trihydroxy bases. The fatty acids compose of mainly alpha-hydroxy fatty acids. Using external calibration method, the major cerebroside found in plant was quantified. This is the first report of sphingolipid content in most of the studied species.