An enzyme-linked immunosorbant assay using monoclonal antibody against bacoside A₃ for determination of jujubogenin glycosides in Bacopa monnieri (L.) Wettst.

BACKGROUND

In Ayurvedic medicines, Bacopa monnieri (L.) Wettst. (brahmi) is known as a medicinal plant used for memory enhancement. Its active compounds are classified as pseudojujubogenin and jujubogenin glycosides. Owing to the lack of chromophore in the saponin glycoside structures, HPLC-UV-vis gives low sensitivity for determination of such compounds. In the case of the detection of small amounts of saponin glycosides, immunological assay could be a suitable method.

OBJECTIVE

To develop and validate a sensitive enzyme-linked immunosorbant assay (ELISA) using monoclonal antibody (MAb) against bacoside A₃, the major jujubogenin glycoside found in brahmi.

METHODS

An immunogen was prepared by conjugating bacoside A₃ with a bovine serum albumin (BSA). To determine its immunogenicity, the ratio of hapten in bacoside A₃-BSA conjugate was determined by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). After immunisation in mice, hybridomas secreting MAbs against bacoside A₃ were produced by fusing the immunised splenocytes with SP2/0- Ag14 myeloma cells. The antibody was raised specifically against jujubogenin glycosides. The ELISA using anti-bacoside A₃ MAb was developed.

RESULTS

Bacoside A₃ in the range of 3.05-97.70 ng mL⁻¹ could be detected by ELISA using anti-bacoside A₃ MAb. The assay showed a detection limit of 0.48 ng mL⁻¹ (0.517 nm). The validation study showed that the method was precise, accurate and sensitive. Interestingly, the MAb showed cross-reactivity with the other jujubogenin glycosides, bacopaside X and IV. However, it did not show cross-reactivity with any of pseudojujubogenin glycosides.

CONCLUSIONS

The study demonstrated that ELISA using anti-bacoside A₃ MAb can be used for determination of total jujubogenin glycosides in brahmi.