PDF
(Download)
|
- Hibiscus (Hibiscus sabdariffa, Malvaceae)
- Phytochemistry
- Pharmacology
|
Date:
03-31-2015 | HC# 091424-517
|
Re: Hibiscus Extracts Contain a Wide Range of Bioactive Compounds and Provide a Myriad of Potential Health Benefits
Da-Costa-Rocha I, Bonnlaender B, Sievers H, Pischel
I, Heinrich M. Hibiscus sabdariffa L.
– a phytochemical and pharmacological review. Food
Chem.
December 15, 2014;165:424-443.
Hibiscus
(Hibiscus sabdariffa, Malvaceae) is a
shrub that grows up to eight feet tall and has showy flowers and large edible calyces.
Flowers, leaves, and seeds of this tropical or subtropical plant have been used
in traditional medicine and as a tea, food source, and flavoring. Hibiscus is thought
to have been in cultivation for approximately 6000 years. Its native
distribution is uncertain because it has been cultivated in so many regions of
the world for such an extensive period of time. Some sources suggest that hibiscus
is native to western Sudan. Hibiscus has two main cultivated varieties; H. sabdariffa var. altissima is primarily used as a source of fiber, while H. sabdariffa
var. sabdariffa is used for human
consumption and, occasionally, as a source of fiber.
Hibiscus calyces have been used traditionally for
tea, fermented drinks, and desserts. The leaves and shoots are eaten raw or
dried, while seeds are ground into meals, roasted and eaten, or used as a
coffee (Coffea spp., Rubiaceae) substitute.
The leaves and calyces are also used in traditional medicine in many countries
as diuretics and for sore throats, hypertension, liver disorders, and cardiac
disease.
Several countries grow and export hibiscus, and the quality
of the plant material is dependent on the country of origin. The highest
quality hibiscus material is grown in Thailand and Sudan. China is the dominant
supplier of hibiscus to the United States. Currently, only a few countries
provide Fair Trade, organic hibiscus, e.g., Egypt and Burkina Faso.
The calyces, leaves, and seeds of hibiscus are rich
in vitamins and minerals. Calyces contain vitamin C, β-carotene, calcium,
and iron. The leaves also contain high levels of iron and β-carotene and, in
addition, thiamine, riboflavin, and ascorbic acid. Hibiscus seeds are rich in
fat and protein and also in numerous minerals, including potassium, calcium,
and magnesium.
Hibiscus calyces
contain a large number of bioactive compounds
that include organic acids, anthocyanins, polysaccharides, and flavonoids. The
concentration of these compounds varies with tissue, genetic origin of the
plant material, and growing, harvesting, and post-harvesting conditions. The
main organic acids in hibiscus tissues are citric acid, hibiscus acid, malic
acid, tartaric acid, and hydroxycitric acid. Hydroxycitric acid and hibiscus
acid are the principle organic acids found in calyces and leaves. The major
anthocyanins present in leaves and calyces are delphinidin-3-O-sambubioside and cyanidin-3-O-sambubioside. Cyanidin-3-O-glucoside also occurs in high
concentrations within the leaves and calyces. Hibiscus tissues contain a wide
range of flavonoids and their derivatives, primarily as flavonols and
flavanols in simple or polymerized form.
The authors list 33 separate flavonoids and phenolic acids identified in
various studies. Seeds have high concentrations of ergosterol. Flowers and calyces
contain high concentrations of protocatechuic acid, hibiscitrin, caffeic acid,
and gallocatechin gallate. Leaves are particularly rich in ellagic acid and
catechins. The mucilage content of calyces and flowers can be up to 28% of the
dry weight with anhydrouronic acid being the most abundant component (up to
80%) of this fraction. There are also a wide range of volatile compounds
identified within the seeds and calyces. As many as 37 different volatile
compounds, including aldehydes, alcohols, ketones, and terpenes, have been
identified from calyces.
Extracts of hibiscus tissues have been shown to
exhibit antibacterial, anti-inflammatory, and antioxidant activity. Much of
their medicinal value is likely related to these characteristics. Both calyx
and seed extracts have exhibited antibacterial properties and have potential in
both cavity prevention and decreasing food spoilage. In addition, one clinical
trial has found that extracts of hibiscus calyx reduced the levels of inflammatory
biomarkers in healthy individuals.
Hibiscus's antioxidant properties are probably the
best characterized, and many of the positive effects seen in vitro and in vivo
are attributed to these properties. Hibiscus extracts have the ability to
scavenge reactive oxygen species and free radicals, provide protection against
oxidative damage, and increase the activity of superoxide dismutase. Hibiscus
extracts have shown protective properties for both liver and kidney tissue in
animal and human systems. In one study in rats, oral administration of hibiscus
extracts resulted in an increase in oxalate excretion in the urine and decrease
in calcium oxalate crystal formation within the kidneys, potentially decreasing
the formation of kidney stones. Several studies have found that hibiscus's
antioxidant properties may be beneficial in preventing and inhibiting the
progression of cancer. In several lines of human cancer cells (prostate,
gastric, and leukemia), hibiscus extracts have shown the ability to inhibit cancer
cell survival, provide protection against tert-butylhydroperoxide-induced cytotoxicity and genotoxicity, and
increase apoptosis.
There is compelling evidence that hibiscus extracts decrease
the risk factors associated with cardiovascular disease and metabolic syndrome
(a number of conditions that increase the risk for
coronary artery disease, stroke, and type 2 diabetes). This may be the result of hibiscus's effect on lipid metabolism and
hypertension. Several animal studies have shown that leaf and calyx extracts
have the ability to lower blood pressure and plasma levels of low-density
lipoproteins, triglycerides, and total cholesterol. In addition, studies in
rats and in humans have found an increase in plasma levels of high-density
lipoproteins after oral administration of hibiscus extract. The effects of hibiscus
on blood lipids and hypertension seem to be dose and duration dependent. Higher
doses over longer periods of time appear to be the most effective.
Some evidence suggests that hibiscus extracts can
also help increase weight loss which, in turn, positively affects other diseases
related to obesity, i.e., diabetes, hypertension, metabolic syndrome, and
cardiovascular disease. There is also evidence that hibiscus tea consumption may
be particularly beneficial in patients with type 2 diabetes, with improvements
seen in lipid profile and hypertension when hibiscus tea is consumed.
Hibiscus has been used as an anti-anemic because
leaves and calyces contain high concentrations of iron, and also because the
low pH of the extracts results in increased absorption of minerals, i.e., iron,
magnesium, and calcium.
Based on its centuries-long history of use in many
countries and at large scale, hibiscus, particularly hibiscus tea, is generally
considered safe for consumption. Adverse side effects, if any, are mild and
transient. No cases of interaction with prescription drugs have been reported.
The two biggest limitations in the understanding of
the positive health effects of hibiscus are the small number of rigorous,
clinical trials and a lack of characterization of phytochemicals present in the
extracts tested. Many of the studies cited in this review were performed in
vitro, within animal systems, or, if in human subjects, were conducted with
very small sample sizes and, occasionally, without blinding or control groups.
The variability in phytochemical composition of hibiscus extracts and the lack
of phytochemical characterization make it difficult to compare such studies, to
come to more rigorous conclusions, and to identify the bioactive compounds in hibiscus.
The authors suggest that rigorous, clinical trials with adequately
characterized preparations would result in a better understanding of hibiscus's
health benefits.
–Cheryl
McCutchan, PhD
|