Abstract (eng)
The aim of this thesis was to obtain an overall picture of the chemical profile of the
essential oil of two plant species, Calytrix exstipulata and Cymbopogon bombycinus.
The GC-MS analyses of the whole leaf oil of Calytrix exstipulata led to the identification
of twenty compounds, predominated by monoterpenes and sesquiterpenes.
The major compounds were α–pinene, β–pinene, valencene and globulol, with a relative
distribution of 25.2 %, 17.9 %, 7.5 % and 4.4 %, respectively. In comparison the
Calytrix exstipulata whole stem oil was predominated by globulol with a relative
distribution of 17.1 %, followed by the monoterpene α–pinene with a relative distribution
of 7.1 %. Fractionation of Calytrix exstipulata leaf oil by normal phase column
chromatography yielded nine fractions, with the majority of fractions containing
monoterpenes and sesquiterpenes. Fraction E gave the highest yield and was further
fractionated. Subfractions E1 and E6 contained sesquiterpenes, while the rest of the
subfractions contained monoterpenes and sesquiterpenes.
Pharmacological assays were performed on the whole oils, on the fractions and
subfractions and were therefore screened for antioxidant and cytotoxic activity as
well. Antioxidant activity was measured using the ORAC assay and the highest antioxidant
activity was observed from subfraction E4 (1185 ± 240 μmol TE/g), followed
by subfraction E1 (1053 ± 20 μmol TE/g), fraction F (865 ± 124 μmol TE/g), and
fraction E (756 ± 24 μmol TE/g). Comparison of the ORAC values with the positive
control epicatechin (20,000 μmol TE/g) showed that none of these tested samples
showed high antioxidant activity.
Cytotoxic activity was investigated against P388, 3T3 and HS 27 cell lines with
chlorambucil as positive control. Highest activity against the P388 mammalian cell
line was observed from subfraction E2 with IC50 value of 0.01 μg/mL, followed by
fraction C and subfraction E4 with IC50 values of 1.63 μg/mL and 1.81 μg/mL, respectively.
In conclusion, fractions E, F and subfraction E4 showed the highest pharmacological
results, which could be attributed to the monoterpene globulol. Globulol was tested
to have cytotoxic activity and it is the most abundant compound in Fractions E, F and
also in subfraction E4.
3
The essential oils of Cymbopogon bombycinus and the Cymbopogon citratus oil were
both rich in monoterpenes only. The major compound of C. bombycinus was geraniol
and was present only in a low percentage in the C. citratus oil. The predominant
compounds geranial and neral in the C. citratus oil were not present in the C.
bombycinus oil. C. citratus oil is already well-studied and was used to compare with
the less explored species C. bombycinus.
Both oils were screened for antioxidant and cytotoxic activity. The ORAC assay determined
that the essential oil of C. bombycinus had higher antioxidant activity than
that of C. citratus, which was attributed to its high geraniol content. On all cell lines,
the whole oil of C. citratus was more cytotoxic than the whole oil of C. bombycinus,
which was attributed to its high geranial content.