Thin-Layer Chromatography - Bioassay as Powerful Tool for Rapid Identification of Bioactive Components in Botanical Extracts

Snezana Agatonovic Kustrin David W

doi:10.4172/2329-6798.1000e120

Abstract

The plant kingdom, both terrestrial and marine, is an underestimated pool of secondary metabolites some of which have enormous therapeutic potential to be an important source of new and unique agents. The identification of active compounds from complex botanical extracts is the main challenge in natural products discovery. The strategy used to discover active substances has been considerably changed in the last decade from the expensive and laborious methods in which bioactivity was studied only after isolation and identification of the components. The new strategy involves only the effective components being isolated and identified. Since chemical separation of the whole sample does not provide information about biological effects, neither do bioassays of the whole sample extracts provide information on observed therapeutic effects for compounds found in these extracts. However, if chemical separation techniques are combined with bioassays the therapeutic effects of individual compounds in a plant extract are able to be assessed. The use of planar chromatography to first separate plant extracts into individual components followed by a bioassay offers a number of advantages. Many samples can be analyzed in parallel on the same chromatographic plate keeping analysis times short and costs low. The high flexibility in detection is accomplished with the use of various derivatization reagents. Hence, direct bioassay on the chromatographic plate makes Thin Layer Chromatography (TLC) screening a powerful tool for rapid identification of bioactive components in crude plant extracts. To search for bioactive compounds in plant extracts with a targeted activity, TLC is hyphenated with an appropriate bioassay enabling direct in vitro biological study of the components that have been previously separated on the plate. Hyphenation of TLC with bioassays, micro chemical detection and further Mass Spectroscopy (MS) identification enables targeted identification of substances from plant extracts. Post chromatographic derivatization by dipping or spraying can be done with either a universal micro chemical derivatization using for example anisaldehyde/sulfuric acid for detection of phenols, sugars, steroids, and terpenes [1] or with selective micro chemical derivatization. The diphenylpicrylhydrazyl (DPPH

Highlights

The plant kingdom, both terrestrial and marine, is an underestimated pool of secondary metabolites some of which have enormous therapeutic potential to be an important source of new and unique agents
To search for bioactive compounds in plant extracts with a targeted activity, Thin Layer Chromatography (TLC) is hyphenated with an appropriate bioassay enabling direct in vitro biological study of the components that have been previously separated on the plate
The bioautography technique is a simplified version of this method where a suspension of a microorganism in a suitable broth is directly applied to the TLC plate by dipping the plate into the broth [4]

Summary

Introduction

The plant kingdom, both terrestrial and marine, is an underestimated pool of secondary metabolites some of which have enormous therapeutic potential to be an important source of new and unique agents. The strategy used to discover active substances has been considerably changed in the last decade from the expensive and laborious methods in which bioactivity was studied only after isolation and identification of the components. If chemical separation techniques are combined with bioassays the therapeutic effects of individual compounds in a plant extract are able to be assessed.

Results

Conclusion