Toxicological Evaluation of Herbal Extracts

Toxicological evaluation is an indispensable companion to every efficacy study described in this phase, since a herbal extract's traditional use history does not, by itself, constitute formal evidence of safety at the doses and durations relevant to modern therapeutic use. Acute oral toxicity testing, following the OECD 423 or OECD 425 guidelines described in detail elsewhere in preclinical pharmacology, establishes a preliminary safety margin and identifies the median lethal dose class of the extract. Sub-acute and sub-chronic repeated-dose toxicity studies, extending over 28 or 90 days respectively, identify target-organ toxicity and establish the No Observed Adverse Effect Level (NOAEL) that anchors subsequent human dose recommendations. Given the widespread traditional use of herbal preparations in reproductive-age populations, reproductive and developmental toxicity testing is of particular importance for herbal candidates intended for chronic or long-term use, and genotoxicity screening (the Ames test and micronucleus assay) is similarly expected wherever a novel isolated phytoconstituent, rather than a well-established traditional preparation, is under development. Because botanical extracts can additionally contain heavy metal or pesticide residue contamination arising from soil, agricultural practice, or processing (addressed in detail in Phase 5), toxicological evaluation of herbal candidates must explicitly distinguish adverse effects arising from the phytoconstituents themselves from those arising from such extrinsic contamination.