Agriculture Reference
In-Depth Information
tests and in a few clinical tests. The phenolic compound PCA isolated from roselle flowers showed
antioxidant, antitumor, and hepatoprotective activities. It has been demonstrated to be an effica-
cious agent in inhibiting the carcinogenic action of various chemicals in different tissues, such as
diethylnitrosamine in the liver, 4-nitroquinoline-1-oxide in the oral cavity, azoxymethane in the
colon, N-methyl-N-nitrosourea in glandular stomach tissue, and N-butyl-N-(4-hydroxybutyl)nitro-
samine in the bladder, in murine models. PCA also shows mild cytotoxicity to PC14 and MKN45
human tumor cell lines and induces apoptosis in human leukemia HL-60 cells by means of the
reduction of retinoblastoma protein phosphorylation and Bcl-2 expression. Thus, PCA may play a
role in dietary chemoprevention.
Hibiscus
exacts have been shown to lower serum cholesterol in men and women in a dose-
dependent manner. In a clinical study, 42 volunteers were observed over a period of 4 weeks. The
volunteers ranged from 18 to 75 years old with cholesterol levels of 175 to 327 mg/dl. Subjects
were randomly assigned to three groups: group I (1 capsule of HSE during each meal), group II (2
capsules), and group III (3 capsules). Serum cholesterol levels were determined at baseline before
the study commenced and at 2 and 4 weeks of the treatment period. In general, taking HSE led
to a significant decrease in serum cholesterol level in subjects from groups I and II after 4 weeks.
After HSE had been administered for 2 weeks, serum cholesterol levels were found to be lower in
all groups (
p
< 0.05 for groups I-III) compared with baseline values by 7.8% to 8.2%. A similar
response was observed, a reduction in serum cholesterol level by 8.3% to 14.4%, after 4 weeks of
taking the supplement. It is important to note that the serum cholesterol level for 71% of group II
volunteers was significantly lowered, with a mean reduction of 12% (
p
< 0.05). The authors con-
cluded that a dosage of 2 capsules of HSE (with a meal) for 1 month can significantly lower the
serum cholesterol level. The observation of lowered serum cholesterol in these subjects suggests that
HSE may be effective in hypercholesterolemic patients.
648
This clinical study validated an earlier
result from feeding experiments in hypercholestrolemic rats.
649
In another clinical study, HSE was shown to possess a significant uricosuric effect.
650
The study
involved a human model with 9 subjects with no history of renal stones (nonrenal stone, NS) and
9 with a history of renal stones (RS) was used in this study. A cup of tea made from 1.5 g of dry
roselle calyces was provided to subjects twice daily (morning and evening) for 15 days. A clotted
blood and two consecutive 24-h urine samples were collected from each subject three times: (1) at
baseline (control), (2) on days 14 and 15 during the tea-drinking period, and (3) 15 days after the
tea drinking was stopped (washout). Serum and 24-h urinary samples were analyzed for uric acid
and other chemical compositions related to urinary stone risk factors. The results when analyzed
showed that serum parameters were within normal ranges and similar between the two groups of
subjects and among the three periods. Vis-à-vis the urinary parameters, most of the baseline values
for both groups were similar. After taking the tea, the trend was an increase in oxalate and citrate
in both groups and uric acid excretion and clearance in the NS group. In the RS group, both uric
acid excretion and clearance were significantly increased (
p
< 0.01). When the fractional excretion
of uric acid (FEUa) was calculated, the values were clearly increased in both the NS and RS groups
after the intake of tea and returned to baseline values in the washout period. These changes were
more clearly observed when the data for each subject were presented individually.
651
The antihypertensive activity of HSE has been demonstrated in several human and animal
studies. Ajay et al. established the probable mechanisms to explain the pharmacological basis of
the observed clinical hypotensive activity of HSE.
652
The study observed the effects of a crude
methanolic extract of the calyces of HSE on vascular reactivity in isolated aortas from SHRs. HSE
relaxed, concentration dependently, aortic rings precontracted with KCl (high K
+
, 80 mM) and
phenylephrine (PE, 1 µM), with a greater potency against the α
1
-adrenergic receptor agonist. The
relaxant effect of HSE was partly dependent on the presence of a functional endothelium as the
action was significantly reduced in endothelium-denuded aortic rings. Pretreatment with atropine
