Walenta et al. 2024 — Arsenic speciation in four mushroom species; discovery of arsenobetaine amide
This study characterized total arsenic mass fractions and arsenic speciation by HPLC-ICP-MS in four mushroom species — Ramaria sanguinea, Amanita muscaria, Boletus edulis, and Macrolepiota procera — collected from contaminated and non-contaminated sites in Austria and Czech Republic. Total As ranged from 0.28 ± 0.01 mg/kg dry mass (Boletus edulis) to 22 ± 2 mg/kg dm (Amanita muscaria). Arsenic species found included arsenobetaine (AB; 8–64% of total As), DMA (0.17–14%), arsenocholine (AC; 1.1–7.4%), and previously unknown species. Critically, a novel nitrogen-containing arsenic compound — arsenobetaine amide (trimethylarsonioacetamide) — was isolated from R. sanguinea and confirmed present in all investigated species by spiking experiments. Inorganic arsenic was detected in some samples; the dominant organic form across species was arsenobetaine. The total As values represent a broad range of contamination levels relevant to human consumption of wild-foraged fungi.
Key numbers
- n = 11 mushroom fruiting-body collections from 4 species
- Total As range (mg/kg dry mass): 0.28 ± 0.01 (B. edulis) to 22 ± 2 (A. muscaria)
- Ramaria sanguinea (high As accumulator): total As 17.2 ± 0.2 mg/kg dm; AB 33%, AC 14%, DMA 0.17%, unknown 15%
- A. muscaria samples: 0.74–22 mg/kg dm; AB 37–48%, AC 1.1–3.5%
- B. edulis: 0.28–1.75 mg/kg dm; predominantly AB + unidentified species
- M. procera: 0.89–4.5 mg/kg dm; AB 40–64%, AC 1.5–2.1%
- Novel species arsenobetaine amide (trimethylarsonioacetamide) identified and confirmed in all species
- Extraction efficiency: 77 ± 11% for water-soluble arsenicals
- Method: HPLC-ICP-MS (PRP-X100 anion-exchange and Reprosil-XR 300 SCX cation-exchange); HR ESI-MS for novel species identification; NIST SRM 1573a and IPE-120 (Agaricus bisporus) CRMs used
- Journal: Analytical and Bioanalytical Chemistry
Methods (brief)
HPLC-ICP-MS for arsenic speciation; carbon dioxide added as optional gas to compensate carbon enhancement effect. HR ESI-MS and NMR for novel species characterization. Freeze-dried mushrooms. Austria and Czech Republic field samples (contaminated and non-contaminated sites). ICP-MS for total As after aqua regia microwave digestion.
Implications
Certification: Mushrooms — including edible species like B. edulis (porcini) and M. procera (parasol) — contain measurable total arsenic; species and site of collection determine concentration range. Novel arsenic species in mushrooms complicate speciation-based risk assessment. Courses: Illustrates that arsenic in land plants/fungi is predominantly organic (predominantly arsenobetaine in mushrooms) and does not follow the same risk rules as inorganic arsenic; discovery of novel arsenobetaine amide demonstrates ongoing gaps in arsenic speciation knowledge. App: Wild mushrooms carry variable As loads; site of collection (contaminated vs. non-contaminated) is the primary driver. Organic As species in mushrooms are generally considered less toxic than iAs, but full speciation data is rarely available. Microbiome: Not applicable.