Christopher Nel
Brandon Walters
Saponins with Nutraceutical Uses
Isolation and characterization of natural products provides access to many organic
compounds that are difficult to synthesize in the lab, but relatively simple to extract. The
perennial creeping plant Gynostemma pentaphyllum, colloquially known in China as Jiaogulan,
has recently been found to contain some compounds that have potential medicinal uses1. G.
pentaphyllum has been shown to contain over 170 varieties of a molecule class known as
saponins1. Saponins are amphipathic glycosides found in many types of plants, and have been
reported to produce a variety of beneficial biological effects when taken as dietary supplements.
Currently, saponins are being studied for their anti-inflammatory, anti-proliferative, hypolipemic,
and immune-potentiating activities1. Anti-inflammatory drugs are substances that act to reduce
inflammation in the body, and thereby reduce pain and swelling. Anti-inflammatory medications
are divided into two main groups, corticosteroids and non-steroidal anti-inflammatory drugs
(NSAIDs). Like NSAIDs, saponins have been shown to reduce inflammation via COX-2
inhibition1.
In the experiment performed by Yang, et al., electronic circular dichroism spectra were
used to determine the absolute configuration of the molecules studied (see Scheme 1 for
structures). The ECD spectra were taken of compounds 1 and 2, and this was compared with a
software-calculated ECD spectrum of molecule 1a. A simple ECD spectrum can be created by
adding Gaussian functions (Figure 1). The mirror-image comparison visible in Figure 2 allows
definitive determination of the structures of 1 and 2 by comparing to the known structure of 1a.
(1) Yang, F.; Shi, H.; Zhang X.; Yu, L. Two Novel Anti-Inflammatory 21Nordammarane Saponins from Tetraploid
Jiaogulan (Gynostemma pentaphyllum) J. Agric. Food Chem. 2013, 61, 12646–12652.
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Christopher Nel
Brandon Walters
Scheme 1. Structures of Saponin Compounds
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Christopher Nel
Brandon Walters
12
Δε (M-1 cm-1)
8
4
Function 1
0
Function 2
ECD Spectrum
-4
-8
-12
200
250
300
350
400
Wavelength (nm)
𝑖=2
−(𝜆−𝜆𝑚𝑎𝑥 )2
ℎ 1
2𝜎2
𝑓(𝜆, 𝟏𝒂. ) = ∑ 𝑓𝑖 (𝜆), 𝑤ℎ𝑒𝑟𝑒 𝑓𝑖 (𝜆) =
𝑒
𝑛 √2𝜋𝜎 2
𝑖=1
Function 1
Position: λmax, 1 = 275 nm
Width: σ1 = 20 nm
Height: h1 = -1
Normation: n1 = 0.0199
Function 2
Position: λmax, 2 = 305 nm
Width: σ2 = 20 nm
Height: h2 = -4
Normation: n1 = 0.0199
Figure 1. ECD spectrum of 1a constructed by superposition of two Gaussian functions.
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Christopher Nel
Brandon Walters
Experimental ECD of 1 in MeOH
Experimental ECD of 2 in MeOH
Calculated ECD of 1a in MeOH
12
8
Δε (M-1 cm-1)
4
0
-4
-8
-12
200
250
300
350
400
Wavelength (nm)
𝑖=𝑚
𝑓(𝜆, 𝑵) = ∑ 𝑓𝑖 (𝜆), 𝑤ℎ𝑒𝑟𝑒 𝑓𝑖 (𝜆) =
𝑖=1
−(𝜆−𝜆𝑚𝑎𝑥 )2
ℎ 1
2𝜎2
𝑒
𝑛 √2𝜋𝜎 2
For N = 1a (λmax,m [nm], m [nm], hm, nm): 275, 20, 1, 0.0199 (m = 1); 305, 20, -4.0, 0.0199 (m =
2). For N = 1: (λmax,m [nm], m [nm], hm, nm): 200 , 8, 16, 0.0499 (m = 1); 208, 10, -13, 0.0391
(m = 2); 216, 8, 9, 0.0495 (m = 3); 255, 12, -0.7, 0.0332 (m = 4); 289. 6.5, 4, 0.0607 (m = 5);
307, 9, 9, 0.0432 (m = 6); 325, 8, 5, 0.0499 (m = 7); 360, 20, -0.5, 0.0199. For N= 2 (λmax,m [nm],
m [nm], hm, nm): 160, 13, -10, 0.0003 (m = 1); 210, 4.5, 3, 0.0887 (m = 2); 223, 5, 1.5, 0.0737
(m = 3); 255, 10, -0.65, 0.0399 (m = 4); 296, 10, 3.5, 0.0397 (m = 5); 308, 6, 4, 0.0629 (m = 6);
320, 8, 4, 0.0499 (m = 7); 370, 20, -0.5, 0.0199 (m = 8).
Figure 2. Comparison of experimental ECD spectra from 1 and 2 to calculated spectrum of 1a.
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