2-hydroxy-2-methylpropionitrile

Additional ecotoxological information

Administrative data

Endpoint:

additional ecotoxicological information

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: scientifically acceptable study with documentation in sufficient detail

Data source

Reference

Reference Type:

publication

Title:

Biochemical basis of the toxicity of manipueira (Liquid extract of cassava roots) to nematodes and insects

Author:

MagalhaesCP, ; Xavier-Filho J, Campos FAP

Bibliographic source:

Phytochemical Analysis 11, 57-60

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

2-hydroxy-2-methylpropionitrile

EC Number:

200-909-4

EC Name:

2-hydroxy-2-methylpropionitrile

Cas Number:

75-86-5

Molecular formula:

C4H7NO

IUPAC Name:

2-hydroxy-2-methylpropanenitrile

Details on test material:

- Name of test material (as cited in study report): acetone cyanhydrin

Results and discussion

Any other information on results incl. tables

Table 1. Biochemical changes associated with the storage at room temperature of the liquid extract of cassava roots

Storage time (h)	pH	Linamarin (mg CN /mL)	Acetone cyanhydrin (mg CN /mL)	Free Cyanide (mg CN /mL)	Linamarase activity U.A.(mL)
0	6.50	365.97 ±21.93	736.27 ± 11.60	94,76 ± 19.10	308,85 ±99.54
6	6.25	nd	317.78± 78,28	402,64 ± 78.58	357,25± 124.92
12	5.60	nd	258.68 ± 65.79	294.00 ± 71.06	366.02 ± 115.89
24	4.60	nd	288.88 ± 78.30	180.02 ± 77.63	372.61 ± 74.87
48	4.60	nd	247.72 ± 53.68	87.00 ± 18.39	444.89 ± 92.97
72	4.60	nd	236.06± 14,67	67.17 ±27.27	493.71 ± 134.02

nd: not detected

The concentrations of cyanogens in fresh and stored cassava extracts are shown in Table 1. As expected, linamarin was rapidly hydrolysed and could be detected only in fresh extract. However, the linamarase activity in the extract remained unchanged throughout the storage period. After 6 h of storage, the concentration of the primary hydrolysis product of linamarin, namely acetone cyanohydrin, dropped to 40% of the initial value and remained unchanged up to 72 h of storage.

The concentration of free, volatile cyanide increased in the first 6 h of storage, then decreased gradually. The stabilization of the acetone cyanohydrin coincided with the gradual change in pH from 6.5 in the fresh extract to 4,6 after 24 h of storage, remaining unchanged up to 72 h of storage (Table 1). The observed stabilization of the acetone cyanohydrin is consistent with the fact that a decrease in pH is known to affect the ability of acetone cyanohydrin to decompose spontaneously (Saka et al.,1997).

Applicant's summary and conclusion

Conclusions:

The presence of defence-related proteins and the concentration of cyanogens in the cell-sap solution of cassava roots (termed manipueira) have been investigated. Within 6 h of storage, all of the major cyanogenic glycoside of cassava, linamarin, had disappeared, while the concentration of acetone cyanohydrin, the breakdown product of the hydrolysis of linamarin, had dropped to 40% of the initial value at zero time and remained unchanged until 72 h of storage. This stabilization of the acetone cyanohydrin during storage seems to be caused both by a drop in pH due to lactic fermentation, which prevents its spontaneous breakdown, and by the absence of alpha-hydroxynitrile lyase in cassava roots. It is concluded that the well-known toxicity of manipueira may be causally related to the stabilization of the acetone cyanohydrin.

Executive summary:

The presence of defence-related proteins and the concentration of cyanogens in the cell-sap solution of cassava roots (termed manipueira) have been investigated. It is demonstrated that manipueira is devoid of lectins, serine proteinase inhibitors and chitinase activity, although very low levels of alpha-amylase inhibitory activity were detected. Within 6 h of storage, all of the major cyanogenic glycoside of cassava, linamarin, had disappeared, while the concentration of acetone cyanohydrin, the breakdown product of the hydrolysis of linamarin, had dropped to 40% of the initial value at zero time and remained unchanged until 72 h of storage. This stabilization of the acetone cyanohydrin during storage seems to be caused both by a drop in pH due to lactic fermentation, which prevents its spontaneous breakdown, and by the absence of alpha-hydroxynitrile lyase in cassava roots. It is concluded that the well-known toxicity of manipueira may be causally related to the stabilization of the acetone cyanohydrin.