Development of Anti-Asiaticoside Polyclonal Antibody-Based Immunoassay and Applications for Centella asiatica Products and Human Serum

A sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibody (PAb) against asiaticoside (AS), one of the triterpenoid saponins found in Centella asiatica (Linn). AS-bovine serum albumin conjugate was immunized to rabbits for producing PAb. The results showed that the antibodies were specific only for AS and very low specific for madecassoside whose basic skeleton is almost the same as AS. The range of the assay extends from 0. 05-25 μg/ml of AS. A good correlation between ELISA and high-performance liquid chromatography methods was obtained when analysis of AS in the crude extracts of plant samples. In addition, the products containing C. asiatica in various preparations were determined AS content by competitive ELISA. The results showed that the product from tea bag preparation gave the highest yield of AS content (35. 59 mg/g dry wt) comparing to other preparations. In order to evaluate the matrix effect of the serum for AS immunoassay, the standard curves of AS in different media were observed. Standard curve of the serum was similar to the water media and both curves showed the measurement range of 0. 20-6. 25 μg/ml. The developed ELISA method can be used for quality assessment of C. asiatica and their products including AS detection in serum samples.