| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Centaurea cyanus | Flower | -- | -- | Jim Duke's personal files. | |
| Centaurium erythraea | Plant | -- | -- | * | |
| Ceratonia siliqua | Fruit | -- | -- | Wealth of India. | |
| Chamaemelum nobile | Plant | -- | -- | * | |
| Chenopodium ambrosioides | Fruit | -- | -- | * | |
| Chenopodium album | Fruit | -- | -- | * | |
| Cichorium intybus | Leaf | -- | 0.5 | -1.1 | * |
| Cichorium intybus | Plant | -- | -- | * | |
| Cimicifuga dahurica | Rhizome | -- | -- | * | |
| Citrullus colocynthis | Fruit | -- | -- | * | |
| Citrus sinensis | Pericarp | 20.0 | 180.0 | 1.0 | * |
| Citrus sinensis | Fruit Juice | -- | -- | Jim Duke's personal files. | |
| Citrus paradisi | Fruit | 25.0 | 35.0 | -0.6 | * |
| Citrus paradisi | Pericarp | 25.0 | 160.0 | -1.0 | * |
| Citrus sinensis | Fruit | 10.0 | 30.0 | -0.8 | * |
| Citrus limon | Fruit | 14.0 | 40.0 | -0.4 | * |
| Citrus reticulata | Pericarp | -- | -- | * | |
| Cnicus benedictus | Plant | -- | -- | List, P.H. and Horhammer, L., Hager's Handbuch der Pharmazeutischen Praxis, Vols. 2-6, Springer-Verlag, Berlin, 1969-1979. | |
| Cnicus benedictus | Shoot | -- | -- | Jim Duke's personal files. | |
| Cocos nucifera | Leaf | -- | -- | List, P.H. and Horhammer, L., Hager's Handbuch der Pharmazeutischen Praxis, Vols. 2-6, Springer-Verlag, Berlin, 1969-1979. |