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Siphonochilus aethiopicus (Schweinf.) B.L. Burtt (Zingiberaceae), commonly
known as wild ginger, is one of the most important and threatened medicinal
plants in South Africa. A study of the pharmacological properties of S.
aethiopicus and the effect of seasonal senescence on antibacterial and anti-inflammatory
properties was undertaken. Water, ethanol and ethyl acetate extracts were prepared
from the leaves, rhizomes and roots of S. aethiopicus plants. The extracts
were tested in a variety of pharmacological assays. Results for the general
screening showed antibacterial and anti-inflammatory activity. Some cytotoxicity
was observed with the aqueous extracts of the rhizome. However, no significant
activity against the herpes simplex virus types 1 and 2, the influenza A virus,
and in the anthelmintic, antischistosomal and biochemical induction assays
were observed. In the microdilution antibacterial assay, no inhibitory activity
against the test bacteria was detected with the aqueous extracts. The ethanol
and ethyl acetate extracts tested showed greater antibacterial activity at
minimal inhibitory concentrations ranging from 0.78 to 3.13mg ml-1 against
the Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) than
the Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae). Little
difference was observed between the ethanol and ethyl acetate extracts, or
between the different plant parts. Ethanol extracts were prepared from the
different plant parts before and after seasonal senescence, and tested for
antibacterial and anti-inflammatory activity. There appeared to be a loss of
antibacterial activity in the leaves with senescence, concomitant with an increase
of activity in the alpha-roots. In the cyclooxygenase-1 assay, the aqueous
extracts showed no significant prostaglandin synthesis inhibition. For the
ethanol and ethyl acetate extracts, the leaves showed the highest levels of
activity at a concentration of 250µg ml-1 per test solution, in both
the cyclooxygenase-1 and -2 assays. Some differences in the levels of anti-inflammatory
activity in the roots following senescence were also observed. There was a
slight loss of activity as a result of drying the rhizome material prior to
extraction. This suggests that fresh rhizome material may be more effective
for medicinal use, although it should be noted that the aqueous rhizome extracts
displayed moderately high levels of cytotoxicity, and may require further investigation.

South African Journal of Botany 2002, 68: 55–61