Complementing classical drug discovery, phytochemicals
act on multiple pharmacological targets, especially in botanical extracts,
where they form complex bioactive mixtures. The reductionist approach
used in bioactivity-guided fractionation to identify single bioactive
phytochemicals is inadequate for capturing the full therapeutic potential
of the (bio)chemical interactions present in such complex mixtures.
This study used a DESIGNER (Deplete and Enrich Select Ingredients
to Generate Normalized Extract Resources) approach to selectively
remove the known bioactives, 4′-O-methyldavidigenin
(1; 4,2′-dihydroxy-4′-methoxydihydrochalcone,
syn. DMC-1) and its isomer 4-O-methyldavidigenin
(2; syn. DMC-2), from the mixture of phytochemicals in
an ethanol extract from Artemisia dracunculus to
determine to what degree the more abundant 2 accounts
for the established antidiabetic effect of the A. dracunculus extract. Using an otherwise chemically intact “knock-out
extract” depleted in 2 and its regioisomer, 1, in vitro and in vivo outcomes confirmed that 2 (and likely 1) acts as major bioactive(s) that enhance(s)
insulin signaling in skeletal muscle, but also revealed that 2 does not account for the breadth of detectable biological
activity of the extract. This is the first report of generating, at
a sufficiently large preparative scale, a “knock-out extract”
used as a pharmacological tool for in vitro and in vivo studies to
dissect the biological impact of a designated bioactive in a complex
phytochemical mixture.