7. Method of Estimation in Biological Sample

Saponins are commonly found in adequate amounts in the root tissue of plant, however recent studies have reported that saponins can be also found in considerable amounts in plant aerial tissues such as leaf and stem. Thus, quantification of total saponin contents in different plant species and organs are very important to understand their biological functions in plant defense. There are several methods have been developed for measuring saponin contents in medicinal as well as crop plant species. The classical colorimetric and biological methods are remain popular methods for saponin quantification. However, biological and colorimetric determinations of saponin contents doesn’t provide accurate information and sometimes might resulted in a misleading information, due the large structural variation of individual saponins not only within different species, but even also among same species. Thus, more sensitive methods have been recently introduced to measure and quantify saponin contents in different plant extracts. High performance (HP)-thin-layer chromatography (TLC) on normal (HPTLC) or reversed-phase (two-dimension, 2D-HPTLC) provides more precise and reliable saponin qualitative information, especially when these HPTLC methods are combined with a computer flying-spot scanner with dual-wavelength. After screening the saponin profile on the TLC, a 2D-analytical software can applied for the quantification of saponin level in plant extracts. However, for reliable measurements a proper saponin standards must be run with the saponin extracts for comparative analysis. Standardization and identification of the peaks by HPLC chromatograms has been also developed for saponin quantification, which relay on the comparisons of the retention times with those observed for authentic standards. On the other hand, there are limited applications of gas chromatography (GC) for quantification and determination of saponin compounds, due to the high molecular weights of the saponin compounds. In this chapter we will discussed some of these methods and the amount of saponin detected in different plant species.