Phytoequivalence in the global marketplace for botanical products (II): Phytochemical composition and antioxidant capacity of standardized commercial Andrographis paniculata extracts

In our effort to understand the phytoequivalence of botanical extracts used in complementary medicines, we examined batch-to-batch phytochemical variability of standardized commercial Andrographis paniculata (Acanthaceae) extracts sourced from India. A. paniculata is used in Ayurvedic medicine as a liver stimulant and for the treatment of jaundice and in Chinese medicine to alleviate body heat and to dispel toxins. Andrographolide and related diterpenoids have been isolated from this species. Commercial extracts are standardized to andrographolide. Significant quantitative variation in andrographolide content has been observed among accessions of A. paniculata from Thailand and India. Manufacturers modify extraction parameters to achieve consistent composition and to compensate for seasonal variability of the starting material. The downside of this method of standardization is the process-induced quantitative variation in other chemical constituents. Using HPLC/DAD/MS-MS, we characterized 12 different batches of standardized extracts sourced from one manufacturer. Results revealed the presence of 21 compounds with variation in number and quantity among the tested batches. Five major constituents, andrographoside, iso-, neo-, deoxy-, and dehydroandrographolide, were tentatively identified. Andrographoside showed maximum quantitative variation (18 fold). In order to determine how the phytochemical differences between the extracts relate to their pharmacological activity, we determined the antioxidant capacity of the extracts using DPPH free radical scavenging and oxygen radical antioxidant capacity (ORAC) assays. Although neither andrographolide nor its major derivatives exhibited DPPH radical scavenging activity, we observed a ˜2.5 fold variation in the EC₅₀ of the whole extracts suggesting that other components contributed to batch-to-batch variation. Ongoing work is directed at the elucidation of the pharmacological significance of batch-to-batch variations to develop better criteria for the determination of phytoequivalence of „standardized“ extracts.