| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Hyssopus officinalis | Leaf | 1.0 | 78.0 | 1.0 | Flavour and Fragrance Journal, 6: 72. |
| Pimenta racemosa | Leaf | -- | 16.0 | -1.0 | * |
| Hyssopus officinalis | Essential Oil | -- | -- | * | |
| Boswellia sacra | Essential Oil | -- | -- | Guenther, E., The Essential Oils, 6 volumes, D. van Nostrand, New York, 1948-1952. | |
| Rosmarinus officinalis | Plant | -- | -- | Leung, A. Y. and Foster, S. 1995. Encyclopedia of Common Natural Ingredients 2nd Ed. John Wiley & Sons, New York. 649 pp. | |
| Apium graveolens | Seed | -- | -- | Charalambous, G. (Ed.). 1994. Spices, Herbs and Edible Fungi. Elsevier Science B. V. Amsterdam. 764 pp. | |
| Ephedra sinica | Shoot | -- | 10.0 | * |