ANNATTO
Source:Bixa orellanaL. (Family Bixaceae).
Common/vernacular names:Achiote, achio-
tillo, annatto, arnotta, and lipstick tree.
GENERAL DESCRIPTION
Shrub or small tree, up to 10 m high; native to
northern South America; extensively cultivat-
ed in tropical areas of Africa, Asia, and in the
West Indies. Part used is the seed, which
contains the coloring principles in an or-
ange-red waxy covering.
Major producers of annatto seeds are India,
Kenya, Ecuador, and Peru; qualities differ con-
siderably depending on sources and seasons.
CHEMICAL COMPOSITION
The coloring principles are carotenoids, most-
ly bixin (oil-soluble) and norbixin (water-sol-
uble), with bixin (especially thecisisomer) in
major concentration (2.5% dry wt.). Norbixin
is the principle component of the water-solu-
ble dyes of annatto and is formed by the
removal of the methyl esters of bixin. Both
a- andb-forms of norbixin are found in water-
soluble annatto dye. ()-Bixin (syn.a-bixin)
is unstable and during extraction is usually
converted totrans-bixin (syn.b-bixin), the
stable isomer, which is also known as isobixin.
Bixin is a monomethyl ester of norbixin (a
dicarboxylic acid); it is readily hydrolyzed by
alkalis during alkali extraction of annatto to
the dicarboxylic acid, norbixin (EVANS;
MERCK).1,2Annatto also containsb-carotene
(6.8–11.3 mg/100 g), apocarotenoids, diapo-
carotenoids, an essential oil (with the sesqui-
terpene ishwarane as the major component),
pentosans, pectin, protein (13–17%), tannins,
and others (EVANS).3,5,6
The coloring principle in oil-soluble annat-
to preparations is free bixin, while that of
water-soluble (usually alkaline) annatto ex-
tracts is an alkali salt of norbixin, commonly
the potassium salt.
Both bixin and norbixin in the free acid
state are insoluble in water but soluble in
organic solvents (e.g., acetone, alcohols) and
aqueous alkaline solutions.
Bixin is one of the more stable natural
yellow colors. However, it loses much of its
tinctorial power gradually on storage, the
process being accelerated by light and heat.
Therefore, the fresh seeds are preferred in
manufacturing processes.
Tinctorial strength of bixin is comparable to
that ofb-carotene, but bixin is the more stable.
Annatto is reported to be most stable at
pH 8, with decreased stability at pH 4–8.^7PHARMACOLOGY AND BIOLOGICAL
ACTIVITIESBroad-spectrumin vitroantibacterial activity
was found from an ethanolic extract of the
dried seeds. An extract of the dried leaves
showed greater potency, and both extracts
were also active againstCandida albicans.^8
However, others report a narrow spectrum of
antibacterial activity from the leaves, and with
activity only found against Gram-positive
bacteria.^9 Awater extract of the leaves showed
platelet antiaggregant activityin vitro.^10 Al-
though bixin and norbixin are carotenoids,
they do not have vitamin A activity.
Norbixin exhibits antioxidant activity
against the deterioration of lipids in bulk olive
oil and in olive oil-in-water emulsions.^11
Administered to rats during and after whole
body irradiation, bixin (200mmol/kg p.o.)
significantly reduced levels of lung collagen
hydroxyproline and liver and serum lipid per-
oxidation values.^12 At concentrations of
1–100mMin vitroin rat spleen lymphocytes,
bixin inhibited the activity of IgE, suggesting
a possible antiallergic effect, and enhanced the
production of IgM.^13TOXICOLOGYAn acute (3-week) oral toxicity study of an
extract of annatto seeds containing 50%40 Annatto