The leaves of the honey herb are sessile, oppositely arranged lanceolate and serrated above the middle. The trichome structures on the leaf surface are of two distinct sizes, one large (4-5µm), one small (2.5µm). The flowers are white with sweet scent and flavour, arranged in an irregular cyma.
The sweet leaf, also known as the honey herb, is nowadays being used as an alternative for sugar. It is also used to treat a gamut of problems from diabetes obesity, hypertension, physical fatigue, and heart burn to even dental decay as the leaves are endowed with significant medicinal properties. A native of Paraguay and named after the Spanish botanist P. J. Esteve, the plant has been used as a natural sweetener for centuries in South America, especially by the Guarani Indians in Paraguay. In Japan, Stevia was approved as a sweetening agent in 1970 and constitutes about 40 percent of the sweetening market. Currently, Japan consumes more Stevia than any other country. China is the world’s largest exporter of the Stevia extract, Stevioside.
In India the cultivation of Stevia in various parts of the country is being promoted by the Karnataka Agriculture University during the last few years. Also the Orissa University of Agriculture & Technology is making efforts to create awareness about the usefulness of Stevia among the people in the area.
Stevia belongs to the family Asteraceae (botanical name Stevia rebaudiana), and is a sub-tropical frost sensitive perennial herb that grows up to about 2 feet in height. It grows on most soils, but prefers a sandy loam or loam that is high in organic matter. Stevia responds favourably to fertilizers with lower nitrogen content and most organic fertilizers work well, since they release nitrogen slowly. The plants may be kept indoors in winter with a fluorescent light left on for 14-16 hours per day, in areas that are prone to frost. Cuttings from wintered plants provide fresh plants for spring although seeds may also be used to grow the plant. Since germination rates are poor and seedlings are very slow to establish, it is best grown as an annual or perennial transplanted crop. Stevia prefers partial shade in climates with considerable summer sunshine. Long spring and summer days favour leaf growth while short days trigger blossoming.
Active Constituents and Biosynthesis
One of the major chemical constituent called Stevioside is found in Stevia leaf and attributes to the sweetening of the leaf. The leaf also contains rebaudioside A. In addition to the sweet diterpenoid glycosides, several other diterpenes have been isolated from Stevia. Since these compounds may be part of the waste stream produced during Stevia processing, their availability in large quantities could make them valuable co-products. Recent pharmalogical test on Stevia reveals that Stevioside and rebaudioside A found in the leaf may be successfully used to stabilize carbonated beverages as they are both heat and pH stable. Rebaudioside A is the least astringent, the least bitter, in relation to other high potency sweeteners such as aspartame. In aspartame the bitterness tends to increase with higher concentrations.
Stevia Leaf — a Natural Sweetner
Stevia leaf is about 300 times sweeter than sugar in its natural state and much more when processed. Unlike many chemical sweeteners, Stevia’s flavour is stable when heated. Like any other natural sweeteners as honey and maple syrup, Stevia has its own special flavour and does not taste exactly like sugar. However despite all its sweetness, there is a bitter aftertaste when the leaf, extract or Stevioside powder is placed in the mouth.
Action and Use The Stevia leaf works as a wonderful sugar substitute and used to sweeten jams, dried sea food, gum and ice cream. It is safe for diabetics and hypoglycemics and has neither calories nor carbohydrates, making it suitable for health conscious people (it has only 1/300th amount of calories contained in sugar). Its medicinal uses include regulating blood sugar, preventing hypertension and may be used to treat of skin disorders.
A study conducted at the Department of Endocrinology and Metabolism at Aarhus University Hospital in Denmark reports that Stevioside enhances insulin secretion from pancreas in presence of glucose via a direct action on pancreatic beta cells. No wonder it is considered as a great alternative to sugar and artificial sweeteners for those who have diabetes.
Moreover it actually inhibits dental decay as opposed to sugar, which contributes to it. Less known, but no less remarkable, is the ability of water-based Stevia concentrate to help heal numerous skin problems, including acne, seborrhea, dermatitis and eczema. The application of Stevia leaf paste to cuts and wounds brings rapid healing without scarring. Pharmacological research also reveals its use to heal psoriasis, burns and lip sores.
With the worldwide demand growing day by day Stevia represents a new opportunity for researchers and farmers alike. Since a ready market exists for Stevia efforts need to be upgraded to promote the cultivation of the plant in different parts of India.