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Since 1971, many toxicities have been reported in animal studies particularly using Wistar
rats fed on unboiled palmyrah flour (odiyal). The studies mainly contained reports on
neurotoxicity and hepatotoxicity. In an attempt to duplicate pioneer studies done in 1971
with Wistar rats, showed that the animals did not consume 100% flour. Therefore the
studies were commenced using a mixture of WHO recommended rat feed and palmyrah
flour (50:50 and 30:70). Neurotoxic symptoms were visible within five days. This was
accompanied by an elevation of AST (p= 0.040) but not an elevation in ALT (p= 0.396).
Studies showed that toxicity varied from site of sampling (Kalpitiya> Mannar> Jaffna).
Further, Wistar rats (effect shown in 5 days) seemed to be affected before than IeR mice
(symptoms in 8 days). The symptoms were the same as those observed in the past studies,
such as ruffled coat, muscle incoordination, characteristic fits, coordinated spasms, falling
over backwards, immobility of hind limbs, and finally death. In addition to this, it was
observed in this study that the animals were subject to hyper-excitation to touch and
pharaphymosis.
The next part of the study was to determine how palmyrah flour could be detoxified. The
flourfrom boiled Kottaikilengu (Plukodiyal) or other wet heat processes (steaming) did not eliminate the toxicity. Although the toxin is very soluble in water, washing of odiyal did
noteliminate toxicity, but rather reduced it. These studies were conducted using traditional
palmyrah food processing methods. However dry heat at 80°C for 45 min removed the
toxicity(both hepatotoxicity/ neurotoxicity). Hepatotoxicity was judged by histopathology
on liver by Haematoxylin & Eosin staining and Oil Red 0' staining. There was periportal
fattydegeneration and hepatocellular hydropic degeneration at 40°C heat treatment on light
microscopybut not in the 80°C treated sample.
The water extract of palmyrah flour produced neurotoxic symptoms, hepatotoxic
symptoms (histopathology) and elevation of AST value to l04.3±23.1 (p=O.0261).
Howevermethanol extract did not extract the toxin. The water: methanol extract showed
onlysub-clinical symptoms and AST value 95.5 ± 22.9, (p=O.044)
The next line of the study was to purify the toxin. Fold purification by Medium Pressure
Liquid Chromatography was 375. The activity appeared only in the water fraction.
Although the dose was theoretically high, the unabsorbed eluate obtained from cation
exchange resin showed neurotoxic effects in very low intensities. This indicated that either
some of the toxin is lost during separation or both fractions (unabsorbed and absorbed)
should be present giving a synergistic effect. Thin layer chromatography of the toxic
fraction showed spots at RFO.15 in addition to the normal sugars of palmyrah. The spot at
the R, 0.15 was absent in the non-toxic fraction. It appears possible that this may be one of
the compounds that contribute to toxicity.
The histopathology of rats provided evidence for toxicity to the liver and this would
explain the hepatotoxic effect. Other workers had shown that the mitochondria are affected.This will explain the elevation of AST levels but not ALT levels. No lesions in
the brain or spinal cord were observed when viewed macroscopically. It is hypothesized
that the toxin is a mitochondrial toxin that gives both the hepatotoxic effect and the
neurotoxic effects as both the muscle and the nerve have the highest number of
mitochondria that would be one explanation for the neurotoxic effect. However, this could
notbe confirmed due to the non-availability of electron microscopy to show mitochondrial
damage in muscle and nerve tissue. Another interpretation is that the neurotoxic effect is
an extreme manifestation of the hepatotoxic effect. Whatever the case it seems that the
neurotoxin and hepatotoxin are whole or part of the same molecule. This explanation
requiresthat the neurotoxic effect is a result of the hepatotoxic effect; brought about as a
resultof mitochondrial damage to liver mitochondria, which could affect many pathways
includingthe urea cycle.
