Abstract:
Moraea pallida (yellow tulp) poisoning is economically the most important intoxication
of livestock in South Africa. Poisoning varies according to locality, climatic conditions
and growth stage of the plant. The primary objective of this study was to determine the
concentration of the toxic principle, epoxyscillirosidine, in yellow tulp leaves and to ascertain
the variability of epoxyscillirosidine concentrations within and between different locations. A
secondary objective was to utilise Geographic Information Systems in an attempt to explain
the variability in toxicity. Flowering yellow tulp plants were collected at 26 sampling points
across 20 districts of South Africa. The leaves of five plants per sampling point were extracted
and submitted for liquid chromatography/mass spectrometry analysis. A large variation in
mean epoxyscillirosidine concentrations, ranging from 3.32 μg/g – 238.27 μg/g, occurred
between different geographical regions. The epoxyscillirosidine concentrations also varied
tremendously between individual plants (n = 5) collected at the same sampling point, with up
to a 24 times difference between the lowest and highest concentration detected. No generalised
correlation between epoxyscillirosidine concentrations and soil elemental concentrations
could be established. However, samples obtained from the north-eastern part of the sampling
region tended to have higher epoxyscillirosidine concentrations compared to samples obtained
from the south-western part of the sampling region. Higher toxin concentrations in the northeast
were associated with statistically significant higher soil concentrations of iron, bismuth,
bromide, cadmium, chromium, rubidium, tellurium, thallium, titanium and zinc, whilst soil
concentrations of strontium and soil pH, were significantly lower. This study corroborated the
contention that epoxyscillirosidine concentration in yellow tulp fluctuates and may explain
the variability in toxicity.
