Michael O. Monanu

Thiocyanate levels of mainly dietary origin in serum and urine from a human population sample in Port Harcourt, Nigeria

Thiocyanate levels were determined in serum and urine samples obtained from a human population sample of healthy non-smoking volunteers (aged between 14 and 30 years) of both sexes known to eat gari-based meals at least once a day. The samples were collected before and 3–4 hours after a gari- or rice-based meal. The values obtained before the test meals showed a wide variation, ranging between 39.20±1.95 to 160.95±8.06 µmol/l of serum, and 81.92±9.78 to 294.01±14.70 µmol/l of urine. For each volunteer, the serum and urine thiocyanate were affected by the test meals. Average increases of 18 and 20% were observed for serum and urine thiocyanate, respectively, following a gari-based meal. A rice-based meal produced, on the average, 10% decrease in both serum and urine thiocyanate. No significant effect of sex or age on the thiocyanate levels was observed. The gari samples used in the study, as well as random samples from the locality of study, had no detectable thiocyanate but contained between 0.013 and 0.015 mg cyanide per kg of gari. These findings indicate that conversion to thiocyanate is a significant pathway in the metabolism of HCN and contributes significantly to thiocyanate found in body fluids and tissues of man. In addition, support is provided for the possible involvement of the sulphurtransferases in the process of cyanide detoxication.

Whole blood cyanide levels of mainly dietary origin in a human population sample in Port Harcourt, Nigeria

Whole blood cyanide levels in a human population sample of volunteers known to each gari-based meals at least once a day were determined. The most widely eaten cassava product in the area of research is gari. The mean blood cyanide obtained for healthy normal volunteers was 0.294 ± 0.09 μmol/L while the value for sicklers was 0.398±0.008 μmol/L, indicating the possibility of reduced rate of metabolism and excretion of cyanide by sicklers as compared to non-sicklers.Investigation of post-absorption distribution indicated that whole blood cyanide increased by 0.014 μmol/L, 3–4 hours after a gari-based meal in normal volunteers. A decrease of 0.012 μmol/L occurred after a whole-rice meal. The increase in plasma cyanide 2–3 hours after a gari-based meal was about 25% more than the increase in erythrocyte cyanide suggesting a significant contribution of plasma cyanide to whole blood cyanide levels. 0.013–0.015 mg cyanide per kg of gari was determined for samples of this staple food in the locality of research.