Anti-bacterial and anti-inflammatory activity of medicinal plants used traditionally in Lesotho.
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Date
2003
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Abstract
A significant potion of the population in Lesotho relies on traditional medicine to meet
its health care requirements. Traditional healers and herbalists were interviewed
from Qacha's Nek (Highlands) and Mohale's Hoek (Lowlands) districts in Lesotho on
plants used by the Basotho in traditional remedies. Fifteen plants were reported to
be used for bacterial infections while thirteen plants were used for diseases
associated with inflammation . Plant roots were most often used to make water
extracts. Mainly high altitude plants are used with lowland healers obtaining most of
their plant material from the highlands, either by collecting them or buying them from highland gatherers.
Leaves and roots of plants used to treat bacterial infections were extracted with
hexane, methanol and water and the respective extracts screened at 100 mg ml¯¹ for
anti-bacterial activity using the disc diffusion bioassay. Seven species displayed very
high anti-bacterial activity against both Gram-positive and Gram-negative bacteria. A
number of plant extracts had medium inhibitory activity, mostly against Gram-positive
bacteria. This activity was mainly found in the root extracts. Six of the thirteen plants
screened for anti-inflammatory activity using the cyclooxygenase-1 (COX-1)
bioassay had activity above 90%. Hexane and methanol extracts were the most active while water extracts usually had lower activity.
Malva parviflora, Eriocephalus punctulatus and Asparagus microraphis exhibited
high anti-inflammatory activity from hexane, methanol and water extracts made from
leaf and root material. High anti-bacterial activity was also recorded from M. parviflora and E. punctulatus hexane, methanol and water extracts. An investigation
on seasonal variation and plant part substitution in medicinal activities for these plants was carried out.
Extracts of M. parviflora collected between June 1999 and July 2001 showed
variation in anti-bacterial activity. Extracts made from leaves and roots inhibited the
growth of both Gram-positive and Gram-negative bacteria. More bacterial strains
were inhibited by extracts made from roots collected in cooler months. However, a
trend in seasonal activity was not evident for either the roots or leaves because there
was no detection of activity in some of the extracts made within the same months or
seasons of the adjacent years. Variation in anti-inflammatory was detected for M.
parviflora extracts. E. punctulatus leaf extracts did not exhibit any seasonal variation
in anti-bacterial activity. Anti-inflammatory activity of E. punctulatus showed seasonal
variation with the highest activity noted when material was collected during the
cooler months and a decline in activity when collections were made during the
warmer months. Hexane, methanol and water extracts made from leaves and roots
of A. microraphis did not show any seasonal variation in anti-inflammatory activity.
Thus, M. parviflora and E. punctulatus should be collected during the cooler months
while A. microraphis can be collected throughout the year. Traditional healers,
herbalists and vendors need to be encouraged to use aerial parts in substitution of ground parts which are reported to be highly utilized.
Effect of storage on anti-bacterial and anti-inflammatory activities of M. parviflora, E.
punctulatus and A. microraphis were monitored. Dried, ground leaf and root material
of the three plants was stored in a cold room, at room temperature and in the Botanical Garden where the material was exposed to high and large changes in
temperature. Dried hexane and methanol extracts made from leaves and roots of
these plants were stored in a cold room and at room temperature. Initially, storage of
the plant material under the three storage conditions caused an increase in antibacterial
activity of the hexane, methanol and water extracts made from leaf and root
material of M. parviflora and E. punctulatus. Storage for a longer period resulted in a
decrease in inhibitory activity. TLC fingerprints developed from hexane and methanol
extracts made from M. parviflora and E. punctulatus stored in a cold room and at
room temperature showed a consistent number and colour of spots during the initial
storage period. Prolonged storage resulted in a decline in the number and colour of
detected spots. The stored hexane and methanol extracts made from leaves and
roots showed a similar trend of increases and decreases in anti-bacterial activity as
well as changes in spots with the storage of the extracts. Testing of the effect on anti-inflammatory activity of hexane, methanol and water extracts made from leaves and roots of M. parviflora, E. punctulatus and A. microraphis showed no change in inhibitory activity of hexane extracts obtained from the material and the extracts stored at the three storage conditions. Methanol and water extracts made from leaves exhibited an increase in activity with prolonged storage. Generally, the stability of the inhibitory activity was longer for the stored dried material than the plant extracts. Isolation of biological active compounds from M. parviflora was not successful due to
loss in anti-bacterial activity as a result of collection of plant material from a different
locality. Anti-inflammatory compounds could not be isolated due to insufficient amount and the synergistic effect of the active compounds . The purified compounds
exhibited loss of activity following HPLC purification which then re-appeared upon recombining
the fractions. A number of compounds were detected from essential oils
of E. punctulatus using GC. Fractions containing these compounds gave positive
anti-bacterial activity in the disc-diffusion , bioautographic and MIC bioassays as well as high anti-inflammatory activity with COX-1 and COX-2 anti-inflammatory bioassays. No anti-inflammatory compounds were isolated from A. microraphis.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.
Keywords
Medicinal plants--Lesotho., Botany, Medical., Traditional medicine--Lesotho., Antibacterial agents., Theses--Botany.