PARTE UTILIZADA= Used part: Hojas, planta entera. 

ACCIÓN FARMACOLÓGICA= Pharmacological action: Para combatir la diabetes. 

COMPOSICIÓN QUÍMICA= Chemical composition: El principal componente de la yerba dulce es el esteviósido (5-13% del peso en seco) el cual se encuentra en mayores concentraciones en la etapa previa a la floración. Los ejemplares sudamericanos y mexicanos son los más ricos en esteviósido, en cambio los ejemplares provenientes de China apenas alcanzan el 5 ó 6%. Se trata de una sustancia soluble en agua y en etanol, de color blanco y sabor mentolado amargo. Otros componentes: rebaudiósidos A, B, C, D, E, F, G, y H (2-3%); dulcósidos A y B; esteviolbiósido; los cuales también han demostrado poseer poder edulcorante (kinghorn and Soejarto, 1991). Contiene además resinas y un aceite esencial conformado por alfa-bergamoteno, bisaboleno, borneol, cardineno, clameneno, centaureidina, carvacrol y muchos otros terpenos. La obtención de los principios activos a través del presurizado (extracción por presión) garantiza las características fisicoquímicas de la materia prima haciendo más fácil su manipulación para la industria farmacética en la elaboración de cápsulas, jarabes o comprimidos. La solución acuosa es estable en medio ácido y neutro, pero no en el alcalino, siendo preferida a la hora de la prescripción que las soluciones alcohólicas. 

ZONA GEOGRÁFICA= Geografical zone: Paraguay.  

DIVERSIDAD GENÉTICA Y MEJORAMIENTO DE PLANTAS MEDICINALES= Medicinal plants and improvement of medicinal herbs

To lay a foundation for molecular breeding efforts, the first genetic linkage map for Stevia rebaudiana has been constructed using segregation data from a pseudo test-cross F1 population. A total of 183 randomly amplified polymorphic DNA (RAPD) markers were analysed and assembled into 21 linkage groups covering a total distance of 1389 cM, with an average distance between markers of of 7.6 cM. The 11 largest linkage groups consisted of 4-19 loci, ranged in length from 56 to 174 cM, and accounted for 75% of the total map distance. Fifteen RAPD loci were found to be unlinked. From the 521 primers showing amplification products, 185 (35.5%) produced a total of 293 polymorphic fragments, indicating a high level of genetic diversity in stevia. Most of the RAPD markers in stevia segregated in normal Mendelian fashion. 

ÚLTIMOS AVANCES EN LA QUÍMICA Y ACTIVIDADES BACTERIOLÓGICAS EN LAS PLANTAS MEDICINALES= Medicinal plants, last advances on chemistry and bacteria activities on the medicinal herbs

1) Stevia rebaudiana Bertoni. produces a no. of high-potency low-caloric sweeteners in its leaf tissue.  The sweeteners are diterpene glycosides and range between 30 and 320 times sweeter than sugar.  Stevioside (Steviol glycosides), the major sweetener present in leaf and stem, was first seriously considered as a sugar substitute in the early 1970s by a Japanese consortium formed for the purpose of commercializing stevioside and Stevia exts.  In addn., the sweet steviol glycosides have functional and sensory properties superior to those of many other high potency sweetener that can grow as natural food market in the future.

2) A work has been performed for screening of antimicrobial activity of various exts. from calli grown in presence of different growth hormones and plantlets obtained from micropropagation.  Calli grown on MS medium supplemented with auxins like IAA, IBA, GA, 2,4-D, in different solvent system were screened for potential antimicrobial activity against bacterial and fungal strains.  Results were compared with com. stevia powder.  It was obsd. that Et acetate exts. of callus obtained on 2-4-D + IAA showed antibacterial activity against Staphylococcus aures.  Remaining exts. were not proved as a potential source for antibacterial activity against test organisms.  Methanol and Et acetate ext. of the calli and tissue cultured plants showed antifungal activity against Alternaria alata.  Some exts. were worked as a stimulative for Aspergillus sp.

3) Stevia rebaudiana is an introduced crop in India.  The leaf and its ext. although sweet have a bitter after taste that precludes com. acceptability.  The compn. of the leaf reflected a high nutritive value and polyphenol concn. averaging 4.15% by wt. of dried leaf.  Variably processed exts. enriched with polyphenols, pigments and a mixt. of both were evaluated for sensory attributes by a semi trained panel when added to coffee and lime juice.  Presence of polyphenols influenced the acceptability of the sweeteners marginally, while chlorophyll was found unacceptable in any of the exts.  The antioxidant activity of the exts. was synergistic when it was mixed with coffee and lime juice.  Complete purifn. of stevia leaf exts. to obtain pure glycosides is not necessary for it to become a com. acceptable sweetener.

Summary
Stevia rebaudiana (Compositae) is a South American medicinal herb native to Paraguay, although it can also be found in Northeastern Argentina and Brazil (Mato Grosso do Sul). Widely used as a natural sweetener due to the presence of two compounds, stevioside and rebaudioside, which have shown to possess as much as 200 times the sweetening power of sugar. Due to this fact, S. rebaudiana has also become of great interest in the treatment of diabetes.

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