Both are single components. Stevioside is the most abundant component in traditional varieties, yet high-grade commercial products are all priced on Reb A. The structural difference is one glucose unit: stevioside carries 3, Reb A carries 4, and the molecular weights differ by 162. That one extra sugar unit raises sweetness and pushes bitterness and aftertaste down.
Distribution is a breeding decision
Their share in the leaf is set by variety selection. In traditional varieties stevioside can account for more than half of total glycosides; modern high-RA varieties suppress it and hand the share to Reb A. The difference between varieties is fundamentally a difference in breeding objectives.
| Component | Typical share of total glycosides in leaf |
|---|
| Stevioside (STv) | About 20%-55% |
| Reb A | About 15%-60% |
| Reb D | About 2%-8% |
| Reb M | About 1% |
Table 1 - Typical leaf distribution. Traditional varieties are dominated by stevioside; modern high-RA varieties suppress it and give the share to Reb A.
The price gap comes mainly from composition, not from which product family a supplier organises it into. Stevioside is naturally abundant in the leaf and easy to purify, so products with a high STv share are cheaper. Reb A has to be raised through breeding and recrystallisation, and every additional purity step costs money, which is why the RA series is more expensive. At the same total glycoside content, the higher the Reb A share, the higher the price.
A quotation that says only “steviol glycosides 95%” cannot be priced properly; the component composition has to come with it. At 95% total glycosides, a 60% Reb A product and a 97% Reb A product are two different price levels. If a customer is working backwards from the regulatory limit to an allowable dose, the calculation also has to use the component composition - see steviol equivalent conversion factors.
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Ask for the component table, not just the total glycoside figure.
Primary sources: GB 2760-2024 (steviol equivalent basis)
Related products: Reb-A Series · Optimvia Reb-M / Reb-D