A validated UHPLC-CAD method for quantitative determination of Astragaloside VII

Astragaloside VII (AST VII) [Fig 1], the first tridesmosidic saponin identified in nature [1], possesses potent immunostimulatory/adjuvant effects [2]. Based on the promising adjuvant properties comparable to current adjuvants (i.e. Alum and QS-21), our team has decided to carry out further studies on AST VII including semi-synthesis studies to discover and develop new human/animal vaccine adjuvants [2]–[5].

Since more than 450 Astragalus species grow wildly in Turkish flora, one of the first challenges of this adjuvant development project is to examine these species by efficient analytical methods to find AST VII rich plant materials and select the rich species for possible cultivation and/or pilot production studies. Thus, aim of this study was to develop a UHPLC method coupled with the Charged Aerosol Detector (CAD) in order to determine AST VII content simultaneously, precisely and sensitively in Astragalus samples. A fifteen minutes method was developed using C18 (100 mm x 4 mm x 3 µm) column, eluting with gradient Water:Acetonitrile mixtures at 0.75 mL/min flow rate. The linear regression analysis of calibration plots showed good linear relationship with r ²=0.9995 in concentrations ranging from 52 to 208 μg/mL. The method was validated for its calibration curve, specificity, precision and robustness. The recovery was found to be in the range of 98.17 to 101.86%. As a conclusion, for the first time, a UHPLC method was validated to quantify AST VII utilizing CAD for its detection.

Fig. 1 Structure of AST VII.

• References

• 1 Kitagawa I, Wang H, Yoshikawa M. Saponin and sapogenol. XXXVII. Chemical constituents of Astragali radix, the root of Astragalus membranaceus Bunge.(4). Astragalosides VII and VIII. Chem Pharm Bull 1983; 31: 716-722
• 2 Nalbantsoy A, Nesil T, Erden S, Calis I, Bedir E. Adjuvant effects of Astragalus saponins macrophyllosaponin B and astragaloside VII. J Ethnopharmacol 2011; 134: 897-903
• 3 Nalbantsoy A, Nesil T, Yilmaz-Dilsiz O, Aksu G, Khan S, Bedir E. Evaluation of the immunomodulatory properties in mice and in vitro anti-inflammatory activity of cycloartane type saponins from Astragalus species. J Ethnopharmacol 2012; 139: 574-581
• 4 Yesilada E, Bedir E, Calis I, Takaishi Y, Ohmoto Y. Effects of triterpene saponins from Astragalus species on in vitro cytokine release. J Ethnopharmacol 2005; 96: 71-77
• 5 Yakubogulları N, Genc R, Cöven F, Nalbatsoy A, Bedir E. Development of adjuvant nanocarrier systems for seasonal influenza A(H3N2) vaccine based on Astragaloside VII and gum tragacanth (APS). Vaccine 2019; 37: 3638-3645