| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Aspalathus linearis | Leaf Essent. Oil | -- | 3200.0 | * | |
| Glycyrrhiza glabra | Root Essent. Oil | -- | -- | * | |
| Centella asiatica | Shoot | -- | -- | Jim Duke's personal files. | |
| Glycyrrhiza glabra | Root | -- | 1.0 | Kameoka, H. and Nakai, K. 1987. Components of essential oil from the root of Glycyrrhiza-glabra. Nippon Gogeikagaku Kaishi 61(9): 1119-1122. | |
| Scutellaria baicalensis | Root Essent. Oil | -- | -- | * | |
| Murraya koenigii | Leaf | -- | 2.0 | * |