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USING HIGH-FIELD NMR TO IDENTIFY THE BIOACTIVE COMPOUNDS IN EXTRACTS OF BLACK RASPBERRY
| Title: | USING HIGH-FIELD NMR TO IDENTIFY THE BIOACTIVE COMPOUNDS IN EXTRACTS OF BLACK RASPBERRY |
| Author: | Fu, Ruiling |
| Description: | Recently, food based approaches for treatment of cancer have been explored. Experimental animal research provided compelling evidence that black raspberries could inhibit the proliferation of oral, esophageal, and colon cancer cells. Studies indicated that black raspberry’s phenolic antioxidants especially the anthocyanins, which are responsible for the fruit color, may play an important chemopreventive role. Nineteen different black raspberries from different farms and cultivars were studied using a high-field nuclear magnetic resonance (NMR) spectrometer that was equipped with a cryogenic probehead. The one-dimensional 1H-NMR spectra were entirely integrated in 0.004 ppm intervals, which created 2101 data bins that were subjected to principal component analysis (PCA). PCA is a statistical technique for pattern recognition that reduces the information in the large data sets. Principal components (PCs) were calculated using both correlation and covariance matrices. In the correlation matrices, which were more sensitive to the minor constituents, the data was normalized by dividing the standard deviation. In the covariance method, the eigenvalues retained the original data, therefore, it gave more weight to larger values. By comparing the cumulative weighting of PCs, the first seven PCs accounted for 84% of the variability in the correlation matrices and 86% of the variability in the covariance matrices. The NMR data from 19 black raspberry samples were used as data for correlation matrices. Regression analysis against the variable of total monomeric anthocyanin content showed that PC1, PC2 and PC5 were important in distinguishing between samples. In the covariance method, PC 1, PC 7, and PC 5 were identified as the most important. According to the absolute eigenvector values, it was found that the 1st and 2nd ranked bins correspond to the methyl peak of cyanidin 3-rutinoside and the 3rd and 4th ranked bins correspond to the methyl peak of cyanidin 3-xylosylrutinoside. Multidimensional and selective excitation NMR experiments were also used to identify the structures of bioactive components. Correlation spectroscopy (COSY), heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC) and selective 1D total correlation spectroscopy (TOCSY) were used to verify the peak assignments of known metabolites and to identify peaks that did not correspond to these known metabolites. Once identified, the additive or synergistic anticancer effects of active compounds can be confirmed by future cancer bioassays. This unique approach will serve as a model to others examining the chemopreventive activity of antioxidant-rich food sources. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=akron1185892825
http://hdl.handle.net/2374.OX/3665 |
| Date: | 2007 |
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