Abstract
Lippia javanica is an erect, small woody shrub that grows up to two metres in
height, popularly known as “fever tea” or “koorsbossie”. It is distributed
throughout southern Africa covering almost the entire country of Swaziland and
large parts of South Africa. Its uses range from that of caffeine free tea with fever
and pain-relieving activities to treatment of microbial infections such as coughs,
colds and other bronchial ailments as well as the basic symptoms of HIV and
AIDS. Topical uses also include disinfection and treatment of skin disorders such
as dermatitis and dry skin, and even for the treatment of lice and scabies.
Furthermore, it is used in combination with Artemisia afra as a remedy against
malaria and as a prophylactic against dysentery and diarrhoea.
In view of the traditional medicinal importance of L. javanica, it was surprising
that not much is known on the polar fraction of this plant. This work was done to
explore the presence of the polar compounds of L. javanica which may contribute
to the plants’ medicinal properties.
The chemical screening was conducted using both the non-polar and polar
extracts of the aerial parts of L. javanica collected from various localities in South
Africa and Swaziland. The screening involved extraction of the aerial parts of the
plant in solvents of different polarities after which TLC showed the presence of
essential oils, phenolic glycosides, amino acids, diterpenoids, triterpenoids and
other phenolic compounds which may include flavonoids. The chemical variation
was further investigated by means of chromatographic techniques such as HPLC
and GC/MS.
The essential oils of L. javanica demonstrated a dramatic variation both in quality
and in quantity within and between natural plant populations. The variation was
found to be random and it was not correlated to the geographical distribution of
this plant. The polar extracts also showed variation in the chemical compounds,
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with clear differences observed between Swaziland and South African
populations. Even among the amino acids a considerable variation was
observed on a geographical level. Although only the aerial parts of the plants
were used in each case, the observed variation could be due to the different
developmental stages of the plants and the different harvesting times.
We have also established that there are different compounds present in
L. rehmannii (toxic Lippia species) and L. javanica which are similar to each other
in appearance and they grow in the same regions and similar environments. The
results demonstrated the importance of performing chemical variation studies
before using these plants and for quality control purposes for marketed products.
The extracts of L. javanica were subjected to the isolation of compounds and
structural elucidation. Two phenylethanoid glycosides, verbascoside β-[(3,4-
dihydroxyphenyl)-ethyl]-(3′-O-α-L-rhamnopyranosyl)-(4′-O-caffeoyl)-β-Dglucopyranoside
and isoverbascoside β-[(3,4-dihydroxyphenyl)-ethyl]-(3′-O-α-Lrhamnopyranosyl)-(
6′-O-caffeoyl)-β-D-glucopyranoside, previously unknown in
L. javanica were isolated. The structures were established by extensive
spectroscopic investigation (IR, UV, FAB-MS, 1D- and 2D-NMR). The discovery
of these compounds gave the most important new insight in this study and they
are known to possess antioxidant activities1. This activity is still to be investigated
in L. javanica.
Mrs. D. K. Olivier
Dr. R. W. M. Krause