Description
Oiticica oil is obtained from the nuts of the tropical tree, Licania
rigida, which is indigenous to the interior regions of Northern
Brazil. L. arborea in Mexico and Central America and L. crassifolia
in Surinam have been the source of similar oils. Limited
attempts to cultivate the oil-producing trees in the United States
and England have been unsuccessful.
The freshly expressed oil is a yellowish viscous liquid, which
gradually solidifies within a few days to a pale green solid with
the consistency of lard. Heating for 30-60 min at 210-220°C renders
the oil permanently liquid. Brazilian natives originally recovered
the oil by boiling crushed nuts and decanting the floating oil.
This inefficient method was replaced by the use of continuous
screw or hydraulic presses to express the oil. Some mills recovered
the residual oil from the presscake by extracting with petroleum
ether or trichloroethylene.
Oiticica oil resembles tung oil in having much of its composition
in the form of fatty acids with conjugated double bonds. The major
source of this conjugated system in oiticica oil is licanic acid
[CH3(CH2)3CH = CHCH = CH-CH = CH(CH2)4CO(CH2)2COOH].
It has the distinction of being the first ketonic unsaturated fatty
acid detected in natural products. According to early reports licanic
acid was said to represent about 75% of the oil. However, further
studies allowing improved analyses suggest that these estimates
were too high. It has been shown that licanic acid constitutes 42%
of the total fatty acid content of oiticica oil; oleic plus linoleic
acids, 23%; eleostearic acid, 14%; stearic acid, 12%; palmitic acid,
7%; and an unidentified unsaturated hydroxy acid, 2%. Thus,
unsaturated fatty acids comprised about 80% of the oil.
Although oiticica oil was used extensively by the coatings industry
when tung oil was unavailable or expensive, currently all drying
oils have difficulty competing with synthetic compositions such
as vinyl, acrylic, epoxy, and urethane resins. Because oiticica oil
no longer enjoys an economic advantage over tung oil, its use in
the paint and varnish industry also appears limited.
