The genus Cinnamomum

90 U.M. Senanayake and R.O.B. Wijesekera
Figure 3.2 GLC chart of commercial cinnamon bark oil on SCOT column.
Following the development of solid injection techniques, Senanayake et al. (1975),
Wijesekera et al. (1975) and Wijesekera (1978) employed this methodology for the study
of volatile constituents of morphologically distinct parts of the cinnamon tree, employing
as little as 15 mg of plant material. Use of this technique has revealed that during
the normal steam distillation, cinnamon volatiles do not undergo any significant chemical
changes, that leaf veins contain more cinnamic aldehyde (30%) than the rest of the
leaf, and many other useful biosynthetic features.
Location of Cinnamon Volatiles in C. verum
C. verum is interesting in that it yields three types of oils from the leaf, stem bark
and root bark. The major constituent in the leaf oil is eugenol, in the stem bark oil it is
cinnamic aldehyde while camphor is the major constituent in the root bark oil. Solid
injection techniques have revealed that the young and old leaves are deficient in volatiles;
only mature leaves (about four leaves below the apical bud) have the general volatile
pattern of the distilled oil. It is also found that the leaf petiole and veins contained more
cinnamic aldehyde than in the leaf lamina. This is in agreement with the view (Neish,
1960) that cinnamic aldehyde will eventually be converted to lignin in the xylem vessels
found in cinnamon stem, petiole and vein.
Cinnamic aldehyde and eugenol are components of the shikimic acid pathway
leading to lignin formation. Cinnamic aldehyde is directly formed by the reduction of
cinnamic acid, the latter being formed from phenylalanine (PA). It was shown that
cinnamic aldehyde gets further reduced to cinnamyl alcohol, which is a precursor of
lignin. Eugenol, due to the absence of a hydroxy group in the allyl side-chain, cannot
readily contribute to the lignin formation. However, Siegel (1955) and Higuchi (1957)
have shown that eugenol is capable of polymerising to lignin-like substances.
Since lignification occurs in the xylem tissues, it has to be established whether synthesis
of cinnamic aldehyde and eugenol occurs in the xylem tissues or whether they are