Comparison of analytical techniques for the identification of bioactive compounds from natural products

Abstract

Covering: 2000 to 2016Natural product extracts are a rich source of bioactive compounds. As a result, the screening of natural products for the identification of novel biologically active metabolites has been an essential part of several drug discovery programs. It is estimated that more than 70% of all drugs approved from 1981 and 2006, were either derived from or structurally similar to nature based compounds indicating the necessity for the development of a rapid method for the identification of novel compounds from plant extracts. The screening of biological matrices for the identification of novel modulators is nevertheless still challenging. In this review we discuss current techniques in phytochemical analysis and the identification of biologically active components.

Fig. 1

Schematic of an integrated UHPLC-UV-MS-SPE-NMR system. Reproduced with permission from Fig. 2, L. W. Sumner et al., Nat. Prod. Rep., 2015, 32, 212–229.

Fig. 2

(a) Scheme of ultrafiltration HPLC-DAD-MS assay for screening for tyrosinase inhibitors. Reproduced with permission from Fig. 1, Z. Yang et al., Anal. Chim. Acta, 2012, 719, 87–95. (b) Scheme of pulsed ultrafiltration-mass spectrometry (PUFMS) to screen chemical mixtures for compounds that bind to a macromolecular receptor. The ultrafiltration membrane traps a receptor in solution, but allows low molecular weight compounds to pass through. Bound ligands are eluted from the chamber by destabilizing the ligand–receptor complex with an organic solvent or pH change. The ligands are characterized with MS. Reproduced with permission from Fig. 1, B. M. Johnson et al., Mass Spec. Rev., 2002, 21, 76–86.

Fig. 3

Typical on-line setup for HPLC post-column receptor assays. Reproduced with permission from Fig. 2, O. Potterat and M. Hamburger, Nat. Prod. Rep., 2013, 30, 546–564.

Fig. 4

Frontal Affinity Chromatogram showing the displacement of 0.25 nM [³H]-Win 551212 (A) in the presence of 1% Zanthoxylum clavaherculis (B) at a flow rate of 50 ml min⁻¹ and the mobile phase composed of ammonium acetate [10 mM, pH 7.4] and methanol (90 : 10, v/v). Reproduced with permission from Fig. 3, Moaddel et al., Anal. Biochem., 2011, 412, 85–91.

Fig. 5

Ligand fishing approach. Protein coated magnetic beads are incubated with a plant extract, washed and then eluted in an aqueous organic buffer. The elution buffer is then analyzed by HPLC-MS.

Fig. 6

Overlaid base peak chromatograms acquired of different solutions (S0–S7) obtained from AGN-TCMB-based ligand fishing from an ethyl acetate extract of E. catharinae. Reproduced with permission from Fig. 5, S. G. Wubshet et al., J. Nat. Prod., 2015, 78, 2657–2665.

Fig. 7

Expanded (50–54 min) base peak chromatogram of crude ethyl acetate extract of E. catharinae loaded on the magnetic beads for ligand fishing (A, black) and the eluents from the fishing experiment (B, red). Inserted to the right are the corresponding MS spectra of peak 12 from the two samples. Reproduced with permission from Fig. 6, S. G. Wubshet et al., J. Nat. Prod., 2015, 78, 2657–2665.