Toxicological Assessment of Herbal Formulations

Abstract

Herbal formulations -- products derived from plant materials including dried herbs, tinctures, standardised extracts, and complex multi-herb proprietary preparations -- are consumed by an estimated 80% of the global population as primary healthcare and by approximately 38% of adults in high-income countries as complementary and alternative medicine. The widespread perception that herbal products are inherently safe because they are 'natural' masks a complex and incompletely characterised toxicological landscape: herbal formulations contain hundreds of bioactive phytochemicals with potential for direct organ toxicity, herb-drug pharmacokinetic interactions (primarily through CYP enzyme induction or inhibition and P-glycoprotein modulation), heavy metal and pesticide contamination in unregulated markets, and adulteration with undisclosed pharmaceuticals. Herb-induced liver injury (HILI) now accounts for approximately 20% of all drug-induced liver injury cases in Western countries and up to 50% in Asian countries where traditional herbal medicines are more extensively used. This systematic review evaluates the toxicological profiles of 247 herbal formulations across eight organ-system toxicity categories -- hepatotoxicity, nephrotoxicity, cardiotoxicity, neurotoxicity, reproductive toxicity, genotoxicity, immunotoxicity, and herb-drug interactions -- from 84 clinical case series and experimental studies. A Herbal Toxicology Risk Index (HTRI) integrating hepatotoxic potential, interaction severity, contamination risk, and regulatory classification is developed. Pyrrolizidine alkaloid-containing plants lead HTRI with score 0.91 (severe veno-occlusive disease; genotoxic; carcinogenic), followed by kava (HTRI 0.84; idiosyncratic HILI) and aristolochic acid plants (HTRI 0.87; aristolochic acid nephropathy