3.2. Structure elucidation
The Fourier transform infrared spectroscopy (FTIR) spectrum revealed the
presence of alkenes, alkanes, hydroxy and aldehyde groups as shown in
Supplementary Figure. Similarly, from QTOF MS/MS data, m/z value
of 349.093from which its molecular formula was determined to be
C20H31NO4. This was in
match with the molecular composition calculated by CHN analysis which
gave a value of C: 0.687, H: 0.089, N: 0.040, O: 0.183. The molecular
weight of the compound was later calculated to be 349.475 g/mol. The
fragmentation data search from LC MS/MS spectrum did not match with any
compound from the database (Figure 1). So, NMR data was required for
structure solution. Hence different NMR spectra were made (Figure 2a and
b.). The structure of the novel compound was resolved from the LC MS/MS
data together with NMR spectra. From the 1HNMR and13C NMR spectra, the isolated compound was confirmed
as
(3S,5Z,7S,8Z)-7-amino-3,5-dihydroxy-2-methyl-13-[(1s,4s)-4-hydroxycyclohexa-2,5-dien-1-yl]trideca-5,8-dien-4-one
(Figures 4 and 5 respectively). The 1H and13C NMR spectra pointed to a compound with long
aliphatic chain and an open ring. Signals at δH 7.26 correlated with δC
67.62 suggested the presence of an NH group. δH at 2.46 to 2.62 and δC
at 29.64 pointed to the presence of CH2 groups. δH at
1.25 to 1.67 indicated CH3 and 5.23 to 5.27 of
C=CH2. This in correlation with δC 19.76 confirmed the
long aliphatic chain. δC at 169.17 indicated a CH=CH and an the absence
of any signal corresponding to aromatic ring inferred towards an open
ring structure and named as Phormidin (Figure 3). Mass difference
between fragments in MS/MS and from FTIR spectra confirmed the presence
of the said groups. Structural search of the available literature
revealed no reported compound and the purified compound was concluded to
be entirely a novel one.