Direct detection of saponins in crude extracts of soapnuts by FTIR

Abstract

Direct detection of saponins in soapnuts (Sapindus mukorossi) using Fourier transform infrared (FTIR) spectroscopy is investigated in this project. Potassium bromide powder was mixed with extracted powder of soapnuts and compressed to a thin pellet for examination process. The outcome of the FTIR spectra of saponin demonstrated characteristic triterpenoid saponin absorptions of OH, C = O, C–H, and C = C, while the glycoside linkages to the sapogenins were indicated by the absorptions of C–O. The significance of this study is that saponin absorption peaks are directly detectable in crude aqueous and 95% ethanol extracts of soapnuts powder using FTIR spectroscopy, thereby eliminating the need of further expensive and exhaustive purification steps. The extracts of soapnuts were screened for saponins along with controls by phytochemical tests, and advanced spectroscopic techniques such as ultra fast liquid chromatography and ultra performance liquid chromatography quadrupole-time of flight-mass spectrometry were also implemented to validate the saponins.

Keywords::

• saponin
• soapnuts
• FTIR
• extraction
• phytochemical

Funding

This work was supported by the Ministry of Higher Education, Kuwait. The authors are grateful to GFS and NUERS, Faculty of Science, Kuwait University, for FTIR analysis [GS 02/01], UFLC & QTOF LC-MS/MS [GS 02/10] and freeze-drying [SRUL01/13].