Comparative analysis of Stevia Rebaudiana, Glycyrrhiza Glabra& Smallanthus Sonchifolius

Written by: Nikolina Nikoalou

Since ancient times, several societies have turned their interest to nature, mainly to botanical plants as medical and heath sources. Currently, a great percentage of the world population uses herbs to cure and alleviate the symptoms of diseases but also to protect the body from any invasive agent. Back in time around 3000 years indigenous people from many cultures used plants for medical purposes with great success, today and mainly developed countries use herbs to face primary needs of medical assistance. Among the thousand plant species that came into surface, some of them possess impressive therapeutic properties with increased demand in the herbal markets.

Initially, stevia rebaudiana or candyleaf is widely known as a potent sweetener in both food and pharmaceutical industries. It is a small seasonal plant which grows to a height up to 30-60 centimeters with the higher percentage of sweetening compounds to be concentrated in the leaves. Leaves of stevia rebaudiana produce components which are known to cause the sweet taste of the plant known as diterpene glycosides. In 1952, the chemical structure of the plant reveled a natural complex of eight diterpene glycosides, including: isosteviol, stevioside (9.1%) , rebaudiosides A-F (3.8%) steviolbioside and dulcoside-A (0.5-1.0%). However, out of various glycosides, rebaudioside-A produce the most desirable flavor profile while stevioside is responsible for the bitter aftertaste due to the presence of some essential oils, tannins, and flavonoids. Also, scientists name these two metabolites as high-potency sweeteners being 300 times sweeter than sucrose. Additionally, further analysis of dried stevia rebaudiana release the presence of proteins, fats, ash, carbohydrates, and crude fiber as well as fatty acid composition of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic and linolenic acid. Stevia is a nutrient rich herb containing substantial amount of other nutrients, like 80-85% water, beta carotene, sodium, iron and magnesium.
Today, the remedy of stevia can help everyone, however there are certain groups who are more likely to benefit from this noteworthy sweetener: diabetic patients, obese and hypertensive individuals as the glycoside components of the plant do not affect the concentration of glucose in the blood making it safer for diabetics and useful in low-calorie diets. Although, stevia rebeudiana have several other therapeutic properties including anti-tumor, antioxidant, anti-microbial and anti-viral, it also improves the function of the kidneys. Still, raw stevia leaves and extracts are not allowed for consumption due to possible side-effects and toxicity of the plant components. Following the dosage guidance, the safe consumption of steviol glycosides for humans is determined to be 4mg/kg body weight per day.

Recent studies showed the metabolic importance of S. rebaudiana as steviol glycosides are metabolized and eliminated through similar pathways in both animals and humans. The major component of this plant Rebaudioside-A in the digestive tract is initially metabolized by colon microbes and converted to stevioside in which is further metabolized to form glucose molecule and steviol. In this way, the released glucose molecules are used by the bacteria in the colon and are not absorbed by the bloodstream reducing the incidence of accumulation.

Globally, stevia is thought to be the solution for a ‘healthier’ alternative sugar thanks to its ability to lower overall calorie intake and help in weigh management. Development of new varieties of S. rebaudiana with a higher content of rebaudioside-A and a reduced content of stevioside is the primary aim of plant breeders for the better utilization of this source of natural sweeteners. Definitively, in future stevia is likely to become a major source of low-calorie sweetener for growing natural food marker.

Another sacred plant originating from the ancient medical history of ayurveda and used both as a medicine but also as a flavoring herb is the glycyrrhiza glabra. Glycyrrhiza glabra is sold under the name licorice (=liquorice) and it is known to be the medicine of ulcers deriving from the sweet root of the plant. Liquorice is one of the most used herb in Western herbal medicine for more than 4000 years as well as in traditional siddha system (India) which is used as a demulcent, laxative for constipation and sweetener. Glycyrrhiza is reported in the literature for its medical assistant to human health as possess anti-inflammatory, antimalarial, and anti-hyper glycemic properties. Also, it detoxifies and protects the liver, used in conditions such as asthma, bronchitis, allergic complains and arthritis. Liquorice can also be used externally for eczema, herpes, and shingles. Importantly, extracts of liquorice are used in treating immunodeficient conditions like AIDS and HIV related diseases (anti-viral properties). Scientists have also revealed that some components of glycyrrhiza own both estrogenic and anti-estrogenic activities, thus it is believed to be an important herb for curing hormonal female problems. Interestingly, a research trial showed that roots of liquorice can be helpful in alleviating the symptoms of severe aliments such as depression and memory loss due to the presence of important components that hold antidepressant and memory strengthening activities. The listed benefits of glycyrrhiza on human health is limitless with ongoing studies to release many more. Despite the importance of glycyrrhiza as a medicine, it has also be used as a food in confectionary industry (sweets, alcohol free drinks) and tobacco industry.

The major bioactive ingredient that makes up the roots of Glycyrrhiza glabra is the glycoside glycyrrhizin (6-10%) which is a saponin that is 60 times sweeter than cane sugar having similar structure and activity as the adrenal steroids. Essentially this compound is comprised of a triterpenoid aglycone, glycyrrhetic acid conjugated to a disaccharide of glucuronic acid.
Both in vitro and in vivo studies demonstrate the importance of glycyrrhizic acid as it inhibits the platelet aggregation, reducing the risk of reactive oxygen species (ROS) generation and suspend the growth of numerous RNA/DNA viruses. In Japan, a combination of 0.2% glycyrrhizin, 0.1% cysteine and 2% glycine showed a potent response in patients suffering from hepatitis B, with the 40% of patients to be completely cured, this highlights the effect of glycyrrhizic acid to improve the tissue pathology by lowering serum liver enzyme levels.

As Hippocrates mentioned this plant is used as a remedy of ulcers, today we know that this is true due to the presence of a special extract known as DGL (deglycyrrhizinated licorice) used for the treatment of gastric ulcers. Flavonoids are the active components of DGL which has shown remarkable results in protective the body by lowering the gastric acidity and reducing the risk of ulcers. As stated before, glycyrrhiza can influence the hormonal levels in females when administered, this action is attributed due to the presence of a class of flavonoids known as isoflavones, isoflavones act by lowering or increasing the estrogen levels when needed. A study performed in 2013 showed that glycyrrhizin can inhibit the action of an enzyme which is responsible for the hibernation of cortisol, aldosterone, and progesterone (5-beta-reductase). Based on this, it can be used in treating mild Addison’s disease and other adrenal insufficiencies.

Trough centuries, no adverse effects of liquorice consumption have been reported. However, excess intake of this herb can lead to the classic symptoms of hypertension, edema formation, muscle weakens and even aldosterone-like syndrome.

Scientists believe that the liquid or tablet form of deglycyrrhizinated is preferable for avoiding the hypertensive side effects and should be taken with empty stomach rather than the capsules (full stomach) as it might inhibit the absorption of drug and be less effective. Finally, doctors recommend the usage of glycyrrhiza for a period of 8 to 16 weeks to reach its optimal effectiveness.

Many studies around the world are focusing on functional foods. Functional foods are those whose action involve in the public health as therapeutic alternatives and their mechanism is highly studied to support this. Yacon (smallanthus sonchifolius) is considered to be a noteworthy example with multiple functions since it possesses some important bioactive compounds that have positive effects on the human body. Yacon is derived from the Andean regions of South America holding an abundant source of fructooligosaccharides (FOS), inulin and phenolic compounds (probiotic). These probiotic substances allow the plant to be highly important in reducing the risk of chronic diseases and providing antimicrobial effects. According to several preclinical and clinical trials, FOS and inulin consumption improves the growth of bifidobacterial in the colon (beneficial bacteria), enchanting mineral absorption and gastrointestinal metabolism while reducing pathogenic bacteria. Additionally, it provides immune boosting activities by promoting a positive modulation of the immune system protective the body from any pathogenic or allergic stimuli.

Yacon (‘yaku’=watery) roots are composed of water which usually exceeds the 70% of the total plant weight while the major portion of the dry matter consists of fructooligosaccharides (6.4%-70%) and phenolic compounds (0.79%-3.08%). After reviewing the benefits of yacon roots, professionals awarded this herb as a dietary supplement for the management of body weight (&obesity), reduction of glycemic index and immune enhancer. A systematic review has proved the effects of FOS in colorectal cancer and obesity as a health-promoting metabolite in human chronic diseases. Fructooligosaccharides are natural food components called fructants which are consisting of linear short chains of fructose molecules (hence the name). Fructose molecules are able to reach the colon intact and stimulate the proliferation of health-promoting bacteria through fermentation to enhance the colon health. Additionally, short chain fatty acids (SCFA), the endoproducts of FOS can also favor the growth of beneficial bacteria like lactobacillus spp and bifidobacterium which are both indicators of a balanced gut flora, while at the same time can inhibit the growth of pathogenic populations.

Aside from this, other important chemicals that make up the effectiveness of yacon plant include: proteins, lipids, saccharides, fibres, calcium, phosphorus, iron, copper, manganese and zinc.

Colorectal Cancer (CRC) is the third most diagnosed type of cancer worldwide. Today, it is still unknown how effective is smallanthus sonchifolius to modulate or suppress CRC.

Recently, a research team studied the chemopreventive effects of yacon roots on dimethylhydrazine (DMH)-induced colon cancer in male rats. The results showed a reduction in cell proliferation and multiplicity of preneoplastic lesions as well as reduction in invasive adenocarcinomas in the group who received 1% of yacon powder. Additionally, the extract of yacon root alone or in combination with lactobacillus acidophilus (symbiotic formulation) showed to reduce the DMH-induced DNA damage in leukocytes. A reduction in apoptotic levels in the group who administered with symbiotic formulation was also observed. Following this study, human intestinal microbiota it is believed to play important role in colon carcinogenesis. As we mentioned before by consuming FOS we can increase the SCFA production which subsequently can act as a substrate or signaling molecule in the regulation of immune response, glucose homeostasis and lipid metabolism. As a result, glycemic levels, body weight and colon cancer risk can be reduced.

Finally, as no patient have mentioned any inconvenience when consuming yacon it is considered to be safe with no-toxic influence on the human health. However, overdosing may cause some discomfort but generally is not life-threating. Symptoms of yacon overdose can include abdominal pain, change in bowel movements and the feeling of being bloating. Scientists strongly advise to store yacon in a cold environment with controlled temperature in order to keep the functional properties of the herb ‘alive’ as a climate change can seriously affect yacon’s health-promoting benefits and make it ineffective.