Overview
Bekalu et al. quantified Fe, Cu, Zn, lead (Pb), and cadmium (Cd) in Nigella sativa L. black cumin seeds collected from three districts in East Gojjam, Ethiopia. The study used microwave-assisted acid digestion followed by flame atomic absorption spectrometry. Lead ranged from 0.11 +/- 0.005 to 0.21 +/- 0.01 mg/kg dry weight and cadmium ranged from 0.09 +/- 0.01 to 0.14 +/- 0.007 mg/kg dry weight across the three districts. All Pb and Cd values were below the WHO herbal-material limits cited by the authors, while Fe, Cu, Zn, and Cd showed significant regional variation.
Key numbers
District mean concentrations
Table 3 reports mean +/- SD in mg/kg dry weight for black cumin seed samples.
| District | Fe (mg/kg) | Cu (mg/kg) | Zn (mg/kg) | Pb (mg/kg) | Cd (mg/kg) |
|---|---|---|---|---|---|
| Dejen | 82.90 +/- 0.75 | 9.18 +/- 0.22 | 55.27 +/- 0.33 | 0.21 +/- 0.01 | 0.14 +/- 0.007 |
| Gozamen | 71.48 +/- 1.89 | 14.39 +/- 0.12 | 71.15 +/- 0.08 | 0.18 +/- 0.02 | 0.12 +/- 0.004 |
| Sinan | 71.38 +/- 1.34 | 22.24 +/- 2.03 | 71.25 +/- 2.79 | 0.11 +/- 0.005 | 0.09 +/- 0.01 |
Source-stated ranges and statistical findings
- Fe: 71.38 +/- 1.34 to 82.90 +/- 0.75 mg/kg.
- Cu: 9.18 +/- 0.22 to 22.24 +/- 2.03 mg/kg by Table 3.
- Zn: 55.27 +/- 0.33 to 71.25 +/- 2.79 mg/kg.
- Pb: 0.11 +/- 0.005 to 0.21 +/- 0.01 mg/kg.
- Cd: 0.09 +/- 0.01 to 0.14 +/- 0.007 mg/kg.
- One-way ANOVA found significant regional differences for Fe, Cu, Zn, and Cd, while Pb was not significantly different across sampling sites.
- The WHO herbal-material limits cited by the source are Pb 10 mg/kg and Cd 0.3 mg/kg; all district means are below those limits.
Methods (brief)
The study sampled Nigella sativa seeds from Dejen, Gozamen, and Sinan districts in East Gojjam, Ethiopia. Samples were subjected to microwave-assisted acid digestion and analyzed by flame atomic absorption spectrometry. Calibration standards for Fe, Cu, Zn, Pb, and Cd were prepared from 1 g/L reference solutions. Calibration R2 values were Fe 0.9991, Cu 0.9982, Zn 0.9987, Pb 0.9987, and Cd 0.9983. Spike recoveries were 94.8-108% across the measured metals. The paper reports LOD/LOQ values in Table 1, including Cd LOD 0.045 mg/kg and LOQ 0.15 mg/kg.
The matrix is black cumin seed on a dry-weight basis. The measured toxic metals are total Pb and total Cd; no arsenic, mercury, chromium, tin, aluminum, uranium, or antimony values are measured.
Implications
Certification: This source provides Ethiopia-market black cumin seed occurrence values for Pb and Cd on a dry-weight basis. It is useful as geographic-context evidence for cumin/black-cumin seed contamination, but it should not be silently pooled with US-market spice data without a market-basis decision.
Courses: Useful for teaching geospatial variance in spice and medicinal-seed contamination: Pb is highest in Dejen, Cd is highest in Dejen by Table 3, and Cu/Zn are higher in Sinan and Gozamen.
App: Adds category-level black-cumin seed values for East Gojjam, Ethiopia. The values are not brand-specific and should be treated as regional ingredient evidence.
Microbiome: Not addressed.
Related evidence
- Lead
- Cadmium
- Iron
- Copper
- Zinc
- Cumin
- Spices
- Herbs And Spices
- Spices
- Condiments (hot sauce, soy sauce, mustard, ketchup, mayonnaise, salsa)
Update history
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