Speciation and Excretion Patterns of Arsenic Metabolites in Human Urine after Ingestion of Edible Seaweed, Hizikia fusiforme

Abstract

Chemical speciation of arsenic in human urine was performed by HPLC separation with ICP-MS detection in order to investigate the urinary excretion patterns of arsenic metabolites after one-time ingestion of an edible seaweed, hijiki (Hizikia fusiforme). A Japanese male volunteer ingested one serving of ca. 15 g (dry weight) of hijiki (containing ca. 0.9 mg of arsenic), and urine samples were collected at 3–5 h intervals for the following 3 days. As a result, different urinary excretion patterns were observed between inorganic and methylated arsenicals. Toxic inorganic As(V) and As(III) were detected in the urine 3 h after ingestion. The highest concentrations of As(V) and As(III) were observed at 6 and 15 h after ingestion, respectively. In contrast, methylated arsenic species in the urine, such as monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenobetaine (AB), began to increase 10 h after ingestion and provided the highest concentrations at 21 h after ingestion. These results indicate that a large amount of As(V) from hijiki is excreted rapidly in urine and some part of it is reduced to As(III) in the human body. As(III) may then be converted to non-toxic methylated arsenic species and excreted in urine later than inorganic ones. It can be concluded from these experimental results that detoxification of arsenic occurs in the human body through the rapid urinary excretion of toxic arsenicals or by conversion to organic methylated ones after ingestion of hijiki.

Metallomics Research Related to Arsenic

“…However, the metabolism of arsenic after ingestion of hijiki had not been clearly elucidated at that point. So, species distribution of seaweeds and inspection of arsenic metabolites in human urine after ingesting seaweeds were investigated by utilizing HPLC/ICP-MS [66]. In Figure 4.22, the chromatograms for the water extract samples for seaweeds (hijiki and wakame) are shown together with that for eight arsenic standard compounds.…”

“…These results suggest that the arsenic metabolite formation reactions due to reduction and The peak of à 3 is the same peak as the unknown peak of à 3 in Figure 4.22, and the peak of à Unknown was a newly appeared one in this experiment. Reprinted with permission from [66] Copyright 2005 The Chemical Society of Japan methylation in liver also occur in human body and that DMA V is excreted as the major urinary arsenic metabolite, as described in Figure 4.19. As discussed in Sections 4.7 and 4.8, it is considered that DMA III may be produced in liver and effluxed into the blood stream but DMA III was not detected in the present experiment.…”

Understanding arsenic metabolism through spectroscopic determination of arsenic in human urine

“…In order to investigate the relationship between diet and As metabolism some workers have monitored As levels in volunteers who were asked to ingest specific types of food. This includes studies where volunteers were asked to consume seafood [20], seaweed [13,71,72] and pure arsenosugar [51]. These studies focused on understanding the urinary excretion pattern of As metabolites subjected to ingestion of seafood by humans.…”

“…The major metabolites after the seafood ingestion were found to be AB, DMA and significant amounts of unidentified metabolites. In another experimental ingestion study, Matsuura and co-workers [71] investigated urinary arsenic excretion pattern after one-time ingestion of seaweed [hijiki (Hizikia fusiforme)]. The authors found that the urinary excretion pattern for inorganic As and methylated As compounds were different.…”