Abstract

Background: Orthosiphon aristatus is a popular medicinal herb because of its pharmacological significance. Therefore, a lot of products formulated from the plant extract are available in the market. However, many phytochemicals in the plant extract are still remained to be unknown.

Objective: The objective of this study was to profile phytochemicals from the plant extracts prepared using water and ethanol in a reflux system for comparison.

Method: The commonly used analytical techniques of acetone precipitation (gravimetry) and vanillin assay (colorimetry) were used to estimate total saponin in the plant extracts. The low dielectric constant of acetone (20.7) was used to precipitate saponins. The phytochemicals in the plant extracts and their respective precipitates were then identified by LC-MS/MS.

Results: Higher amount of precipitate was formed from ethanol extract than water extract. The results of LC-MS/MS revealed that not only saponins, but other phytochemicals, such as phenolic acids, flavonoids, terpenoids and aliphatic acids were also detected in the precipitates. In particular, ethanol extract and its precipitate were found to have higher flavonoids. Acetone precipitation could significantly increase the content of sagerinic acid and rosmarinic acid, as well as polyhydroxylated and polymethoxylated flavones from the water extract.

Conclusion: Acetone precipitation is not specific for saponin, but also any phytochemicals which have lower solubility due to the lack of hydrogen bonding in high dipole moment medium of acetone. Gravimetric acetone precipitation had successfully profiled the phytochemicals in both highly complex water and ethanol based crude extracts.

Keywords: Medicinal herb, bioactive compounds, saponins, vanillin assay, LC-MS/MS, Orthosiphon aristatus.

Graphical Abstract