D.S. Seigler said:
in Biochemical Systematics and Ecology 31 (2003) 845–873
2.2. Cyanogenic glycosides
Many species of Acacia contain cyanogenic glycosides, substances that can release
hydrogen cyanide when the plants are damaged. For this to occur, both the glycosides
and β-glycosidases must be present. Among the known cyanogenic species, plants
have been described that lack both the substrate and the enzyme, that have cyano-
genic glycosides and not the enzymes, that have the enzymes and not the glycosides,
and that have both. This last type is potentially poisonous to livestock. More than
70 species of Acacia have been reported as cyanogenic (Clarke et al., 1990; Conn
et al., 1989; Ebinger et al., 2000; Lee et al., 1989; Seigler et al., 1989). This number
includes 25 from subgenus Acacia and 45 from the subgenus Phyllodineae. Cyanide
has only been reported from a small number of species of subgenus Aculeiferum.
The cyanogens of subgenus Acacia are a series of related aliphatic compounds
derived from valine, isoleucine, and leucine, namely linamarin (3), lotaustralin, pro-
acacipetalin (4), epiproacacipetalin, heterodendrin, proacaciberin, and 3-hydroxyhet-
erodendrin (Maslin et al., 1988; Seigler et al., 1989). An apparently related diol
glucoside, 2-β-d-glucopyranosyloxy-2-methylpropanol (5), was isolated from Acacia
sieberiana var. woodii (Brimer et al., 1982).
In a survey in which approximately 96% of Australian species of subgenus Phyllo-
dineae were examined, 45 species were found positive for cyanogenic potential
(Maslin et al., 1987), most of them in section Juliflorae (Maslin et al., 1988). The
cyanogenic glycosides of these plants are prunasin (6) and/or sambunigrin (7),
derived from phenylalanine. However, an aliphatic cyanogen, heterodendrin, has
been found in two members of subgenus Phyllodineae, A. exilis and A. pulchella
var. reflexa (Seigler et al., 1989). Typically, the cyanogenic species of subgenus
Phyllodineae lack the enzymes needed to hydrolyze the compounds rapidly (Maslin
et al., 1988) and, although cyanogenic species of Acacia are widespread in Australia,
there are few reports of livestock poisoning attributable to Acacia species (Everist,
1981; Maslin et al., 1987).
The African species Acacia caffra and A. hereroensis of subgenus Aculeiferum
also contain the aromatic cyanogens, prunasin and sambunigrin. In addition, her-
barium specimens of A. chariessa, A. klugii, and A. welwitschii proved to be weakly
positive for liberation of hydrogen cyanide with the Feigl–Anger test (Conn et al.,
1989; Tantisewie et al., 1969).