Steviol glycosides come from the leaves of Stevia rebaudiana, a perennial herb in the Asteraceae family native to north-eastern Paraguay. Dry leaves usually contain 5%-15% steviol glycosides; high-yielding varieties grown under strong sunlight at higher latitudes can reach 16%-17%.
The plant grows 60-110 cm tall. The Guarani people of Paraguay sweetened tea and medicinal infusions with it for centuries; it was first formally described and named by the botanist Moises Bertoni in 1899.
The glycosides are found almost exclusively in the leaves. Content in roots and stems is very low.
Worldwide, cultivation is concentrated in China, mainly in Jiangsu, Anhui, Gansu and Xinjiang. In practice the crop is propagated by cuttings in March and harvested and stored from September to October.
Variety and region both move the number
Total glycoside content and component profile differ clearly between varieties, and the same variety can vary widely between growing regions. Take PuXing No.6, a leading variety in Jiangsu and Xinjiang in recent years: dry-leaf total glycosides commonly exceed 14%, yet trial data measured 12.84% in the Hexi irrigation district of Gansu and 16.87% in Bayingolin, Xinjiang - almost four percentage points apart. The variety sets the ceiling; what you actually receive depends on region, climate and harvest date.
| Variety | STv, % | Reb A, % | Reb C, % | Dulc. A, % | Total, % |
|---|
| PuXing No.6 | 5.26% | 9.34% | 1.59% | 0.14% | 16.33% |
| Shoutian No.2 | 1.37% | 9.36% | 1.04% | 0.22% | 11.99% |
| GL No.9 | 1.32% | 11.76% | 2.11% | 0.13% | 15.32% |
Table 1 - Typical component profile by variety (dry leaf). Values move with region and season. GL No.9 is a variety owned by GL Stevia.
Read the three rows together and two things separate them: the total glycoside level, and the ratio of stevioside to Reb A.
Because dry leaf only carries about 12%-15% steviol glycosides, industry has no choice but to run an extraction-and-purification route. Research on the other leaf constituents - chlorogenic acid, isochlorogenic acid, stevia polyphenols and polysaccharides - and their antioxidant and lipid-lowering activity has grown steadily in recent years. In 2023 the National Health Commission of China approved stevia dry leaf under the leaf-vegetable category, so the leaf itself may in future be eaten directly as a functional food.
Related products: Stevia product lines · Reb-A Series · Optimvia Reb-M / Reb-D