INTERACTIONS OF ECHINACEA AND SPILANTHES WITH HUMAN METABOLIZING SYSTEMS

Increasing use of herbal products in recent years demand further studies relating to their safety and efficacy. Since cytochrome P450 enzymes play a major role in drug metabolism, studying their interactions with herbal extracts would be an important step in this direction. In the current study, Echinacea purpurea root and Spilanthes acmella whole flowering plant extracts were tested against CYP2C9, CYP1A2, CYP2A6 and CYP2E1. Both Echinacea and Spilanthes showed moderate inhibition against CYP2C9 while they both failed to show any inhibition towards CYP1A2. Echinacea showed moderate inhibition against both CYP2A6 and CYP2E1 but raw Spilanthes extract did not show any interaction with CYP2A6. It showed mild inhibition of CYP2E1 when used in high concentration. Isobutyl amides, known to be the only bioavailable components of Echinacea and Spilanthes were tested for their ability to inhibit CYP2E1. The four isobutyl amides present in major proportions in the ethanolic preparation of Echinacea purpurea root were isolated and shown to be potent inhibitors of CYP2E1. Spilanthol, the only major isobutyl amide found in the ethanolic preparation of Spilanthes acmella whol