Combination of two spectrophotometric methods for total quantification of steroidal and triterpenoid saponins contents in saponin plants mixtures

Abstract

Saponins are complex molecules constituted of a sapogenin associated with one or more osidic chains. Their properties are used in many industrial sectors such as food, cosmetics, agricultural and pharmaceutical. Depending on saponin plants, the sapogenin could be steroidal or triterpenoid leading to a large diversity of saponins. The control and quantification of total saponins is therefore a challenge due to this structural diversity. In a previous study, we developed a fast and accurate colorimetric method for the total quantification of steroidal and triterpenoid saponins [1]. In strong H2SO4 conditions (50% v/v) with p-anisadehyde, an identical chromophore is formed at 600 nm for all saponins allowing their quantification. Interestingly, utilization of soft H2SO4 conditions (12.5% v/v) with p-anisaldehyde form a chromophore at 425 nm only with the spirostan and furan structures present in steroidal saponins [2]. Coupling the spectrophotometric method at 425 nm with that of 600 nm could permit obtaining steroidal saponins content as well as the triterpenoid saponins content in a mixture of both saponins types. In this study, several blends of Camellia oleifera (triterpenoid saponins) and Trigonella foenum-graecum (steroidal saponins) extracts were assayed with spectrophotometric methods at 425 and 600 nm. Results showed that the values obtained experimentally were relatively close to those found by calculation with a bias which did not exceed 7.7%. This application could have great potential in the industry by example for the standardization of plant material constituted of two saponins types or to unravel plant adulteration issues.