were identified as ellagic acid, corilagin and geraniin, respectively. In the geraniin identification
(compound 3), the observation of methine carbon resonance in upfield regions (δ 46.19 and 51.97) of
the 13C spectrum accompanied with hemiacetal carbon resonance (δ 92.38 and 96.21) and low field
carbonyl carbon signals (δ191.71 and 194.43) indicated the presence of dehydrohexahydroxydiphenoyl
(DHHDP) structure. The DHHDP moiety leads to the observation of complex spectra due to the
doubling of NMR resonances because of its equilibrium mixture of five- and six membered hemiacetal
rings [11]. The use of methanol in the extraction can lead to the formation of a methoxy hemiacetal
instead of the geminal diol for both five- and six membered hemiacetal rings in geraniin. Thus a MS
peak for [M+Na+CH3OH−H2O]+
(m/z value of 989) (Figure 3a) was observed instead of [M+Na]+
(m/z
value of 975) but this formation is reversible to give back geraniin after methanol has been removed
(Figure 3b). The problems associated with the multiplicity of NMR signals of DHHDP moiety were
resolved by reaction with o-phenylenediamine to form the known [13] geraniin-phenazine derivative
(Figure 4) which destroyed the hemiacetal ring.