Blanching alters the phenolic constituents and in vitro antioxidant and anticholinesterases properties of fireweed (Crassocephalum crepidioides)

Objective This research investigated the effect of blanching on the phenolic distribution and in vitro antioxidant and anticholinesterase properties of the HCl-methanolic extracts from fireweed. Methods Phenolic-rich extracts were prepared by extracting the powdered blanched and unblanched fireweed leaves with a mixture of absolute 1 M HCl and methanol (1:1 v/v). The phenolic constituents were analysed using high-performance chromatography coupled to a diode array detector (HPLC-DAD). Furthermore, the extracts' in vitro antioxidant [1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azinobis(3-ethylbenzo-thiazoline-6-sulfonate (ABTS) radical scavenging and Fe2+ chelating abilities and inhibition of Fe2+-induced lipid peroxidation in isolated rat brain] properties and inhibitory effects against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were determined in vitro. Results The HPLC-DAD analysis detected four phenolic acids (gallic, chlorogenic, caffeic and ellagic acids) and three flavonoids (catechin, rutin and quercetin) that were abundant in the unblanched fireweed extract. The findings further showed that the unblanched fireweed extract had higher antioxidant and AChE and BChE inhibitory properties compared to the blanched fireweed extract. Conclusion The increased antioxidant and anticholinesterase properties of the unblanched fireweed extract could be linked to its higher concentrations of the phenolic constituents compared to the blanched firewood. Therefore, blanching leads to a decrease in the antioxidant and anticholinesterase properties of fireweed, as evidenced by a reduction/loss in the polyphenolic content from the blanched fireweed.