Agriculture Reference
In-Depth Information
(1 µM), L-NAME (10 µM), or methylene blue (10 µM), but not indomethacin (10 µM), significantly
blocked the relaxant effects of HSE. Endothelium-dependent and -independent relaxations induced
by acetylcholine and sodium nitroprusside, respectively, were significantly enhanced in aortic rings
pretreated with HSE when compared to those observed in control aortic rings. The results thus dem-
onstrated that HSE has a vasodilator effect in the isolated aortic rings of hypertensive rats. These
effects are probably mediated through the endothelium-derived NO-cGMP-relaxant pathway and
inhibition of calcium (Ca
2+
) influx into vascular smooth muscle cells.
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Toxicity —
The aerial parts of roselle, zobo, or hibiscus flower have been used as a safe tea
substitute and a nutraceutical for centuries without any manifest toxicity. With the popularity of HS
as a long-term food-medicine for the management of elevated blood pressure and hypercholester-
olemia, it became necessary to investigate any possible toxicity in acute animal models and cohort
long-term studies in human subjects. One such study was aimed at assessment of the potential
adverse effects of HSE on sperm morphology and testicular ultrastructure of albino mice. Thirty
adult male albino mice were divided into three equal groups and were given (a) distilled water, (b)
cold
Hibiscus
aqueous extract, or (c) boiled
Hibiscus
aqueous extract.
Hibiscus
extract was admin-
istered orally daily for 4 weeks in a dose of 200 mg/kg body weight/mouse. Twenty-four hours
after the last treatment, mice were decapitated, and the testes and epididymides were excised and
processed for transmission electron microscopy to assess ultrastructural and sperm abnormalities.
The results clearly demonstrated that aqueous extracts from dried calyx of
H. sabdariffa
, either cold
or boiled, altered normal sperm morphology and testicular ultrastructure and adversely influenced
the male reproductive fertility in albino mice.
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Another toxicity study on experimental animals
evaluated the effect of HS on rat liver enzymes and indicated possible hepatotoxicity of prolonged
use of HSE.
654
These finding, although not easily transferable to the human situation, tend to suggest
that
Hibiscus
extract may pose some human risk on prolonged use at high doses. It is interesting to
observe that a later study actually indicated that HSE displayed antihepatotoxic activity when tested
against azathioprine-induced acute liver damage.
655
Commerce —
Hibiscus sabdariffa
still remains a grossly underutilized plant. It is an impor-
tant industrial crop for its fibers, and the demand for roselle fiber is likely to increase as a result of
the rising interest in natural, biodegradable fibers. It has a global market as a colorant for herbal
teas. Its rising profile and application as a nutraceutical agent makes it a commercially dependable
crop. This multipurpose crop provides farmers with food and cash income when other vegetables
have become scarce. Processing generates additional family income, from which women benefit in
particular. Use of roselle as a vegetable or as a beverage should be promoted through research to
improve cultivars, husbandry, and postharvest technologies. Applying rigorous quality standards
for grading, processing, and packaging will boost competitiveness in the international market. The
current market price for HS in the international market is US$2350-2450 metric ton/cost, insurance
and freight (MT/CIF).
Agriculture —
The seedlings for cultivation are collected during thinning, the period of veg-
etative growth when the plants are 6-8 weeks old; branches of about 50 cm long are picked two or
three times. Calyces are harvested manually 2-3 weeks after flowering, usually 4-6 months after
sowing, before the fruit has dried and dehisced. Regular picking prolongs flowering. The calyces
are dried in the shade. When harvested for fiber, stems are cut before flowering, 4-5 months after
planting. Fiber quality declines rapidly after the start of flowering. A single roselle plant may yield
as many as 250 calyces, or 1-1.5 kg fresh weight. In Africa, average yields are much lower and
variable because of environmental conditions and extensive management. Sudan reports an average
yield of dry calyces of 93 kg/ha. In Senegal, maximum production of calyx on a dry weight basis
is 500 kg/ha. Average fiber yields from roselle are 1.5-2.5 t/ha, depending on cultivar and manage-
ment. India reported an average yield of 1.9 t/ha for 1997-2001. Reported seed yields ranged from
200 to 1500 kg/ha.
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