Solid-State 13C NMR of
Solid-state 13C NMR is an excellent way
to investigate what chemical functionality is present in herbal supplements. The
large resonances at 60-105 ppm are due to cellulose/polysaccharides and some
sugars. The peaks in the 0-60 ppm region are aliphatic carbons in fatty acid
chains. Peaks in the 110-140 ppm region are alkene and aromatic carbons, while
peaks in the 140 ppm and 150 ppm region are due to substituted aromatics and
phenolic carbons. Peaks in the 160-200 ppm region are due to carboxylic acids,
esters and amides. Solid-state NMR is a relatively simple technique that involves
no sample preparation and observes the sample carbon chemistry in it's entirety. The analysis
reveals relative amounts of chemical functionality that can be utilized for
product-to-product comparison or batch-to-batch manufacturing comparison. The
chemical specificity of the technique also means that adulterants can readily be
detected and identified.
A few examples of "off the
shelf" herbal supplements are shown below.
Figure 1: 13C CP-MAS NMR of Cranberry
Extract, Green Tea Extract, and Milk Thistle Extract
Figure 2: 13C CP-MAS NMR of Black
Cohosh Root Extract, Echinecea Powder, and Bilberry Extract
Figure 3: 13C CP-MAS NMR of Valerian
Root Extract, Ginseng Extract, Saw Palmetto Extract, Grape Seed, and St John's
Edwards for more details.