| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Gentiana lutea | Root | 6000.0 | 8000.0 | 1.0 | * |
| Gentiana scabra | Root | -- | 500.0 | -1.0 | * |
| Centaurium erythraea | Plant | -- | -- | * | |
| Menyanthes trifoliata | Leaf | -- | -- | * | |
| Trigonella foenum-graecum | Seed | -- | -- | Williamson, E. M. and Evans, F. J., Potter's New Cyclopaedia of Botanical Drugs and Preparations, Revised Ed., Saffron Walden, the C. W. Daniel Co., Ltd., Essex UK, 362 pp, 1988, reprint 1989. | |
| Swertia chirata | Plant | -- | -- | * |