Survey of Phenolic Compounds Produced in Citrus
Experimental Methods

Nuclear Magnetic Resonance (NMR)

NMR was used to resolve two closely eluting flavonoids in our chromatographic profiles: didymin (isosakuranetin–7–O–rutinoside) and poncerin.

¹H NMR (270 MHz, DMSO–d₆) Didymin: d=1.15 (R-Me), 2.57 (3 eq) (3 ax is under the H-b2-eO solvent peak, as are many of the sugar H's), 3.77 (4'-OMe) 4.54 (R-1), 5.01 (G-1), 5.45 (2), 6.23 (6,8), 6.98 doublet (3', 5'), 7.42 doublet (2',6'). Poncerin: d=1.15 (R-Me), 2.80 (3 eq), 3.77 (OMe) 4.48 (R-1), 5.10 (G-1), 5.6 (2), 6.12 (6', 8'), 6.98 doublet (3', 5'), 7.43 doublet (2', 6').

¹³C NMR (270 MHz, DMSO–d₆) Didymin: didymin's spectrum is somewhat weak but resembles naringin's (Agrawal and Bensal 1989, Markham and Ternai 1976) except that it lacks a G-6 peak between 56 and 64 mg/L. This is diagnostic of rutinosides (Markham and Ternai 1976). Poncerin: poncerin contains a G-6 peak at 60.5, which is diagnostic of G-6 in neohesperidosides (Markham and Ternai 1976). The ¹³C NMR spectrum of the phenolic portion of the two compounds resembles that of naringin with the addition of a 4'–methoxy peak at 55.1 mg/L and the following shifted peaks: 113.9 (3', 5') and 128.2 (2', 6').

previous page

next page

United States Department of Agriculture
Agricultural Research Service

The material on this page is in the public domain.

Original posting: April 1, 1999.