Phytochemical analysis and biological study on Sinapis alba L. seeds extract incorporated with metal nanoparticles, in vitro approach

White mustard (Sinapis alba L.) seeds are the most commonly used mustard species in herbal medicine to treat a wide range of inflammatory disorders. Due to its increased bioavailability and lower toxicity, the green biosynthesis of metal nanoparticles (M-NPs) utilizing plant extract as a capping agent has been demonstrated over a number of years. Thus, the current study sought to examine the in vitro biological activity of copper oxide nanoparticles (CuO-NPs) and selenium nanoparticles (Se-NPs) that were biosynthesized using aqueous, methanolic, and petroleum ether extracts from S. alba seeds. Phytochemical and in vitro biological activities (antioxidant, scavenging, anti-diabetic, anti-acetylcholinesterase, anti-arthritic, anti-inflammatory, and cytotoxic activities) were assayed in all prepared extracts before and after being used for the biosynthesis of the M-NPs. It was found that the total methanolic extract possessed the highest biological activities compared to other native extracts. The LC-ESI-MS/MS analysis of secondary metabolites showed that the total methanolic extract contained 7 phenolic acids and 9 flavonoid aglycones. This helped find the active ingredients. We characterized 8 phenolic acid derivatives, 7 flavonoid glycosides, 4 aliphatic glucosinolates, and 3 aromatic aryl glucosinolates in the aqueous extract. Furthermore, the methanolic extract contains the highest concentrations of total polyphenols, condensed tannins, and total flavonoid compounds. The biosynthesized Se-NPs using methanolic extract showed higher in vitro biological activities compared to those of the biosynthesized CuO-NPs. The median lethal dose (LD₅₀) showed that the biosynthesized Se-NPs using the studied extracts appeared safer compared to those of the biosynthesized CuO-NPs. The findings of this study concluded that the total methanolic extract is the most suitable bioresource for biosynthesizing Se-NPs through green nanotechnology, with higher biological efficiency in relation to its metabolite fingerprint.