Flavonolignans are secondary plant metabolites found only in few plant families such as Asteraceae, Fabaceae and Berberidaceae. A good source of flavonolignans is the milk thistle plant, which contains high concentrations especially in the seeds of its fruits. Flavonolignans may have biological activity and beneficial effects that plants rich in these molecules have been associated with for centuries (Romanucci et al., 2018, Valková, 2020).

Structurally flavonolignans display a broad diversity, often containing several chiral centres and therefore occurring naturally as stereoisomers. Flavonolignans are produced by the coupling of a flavonoid with a phenylpropanoid (e.g. coniferyl alcohol), followed by the subsequent coupling with two radicals (Valková, 2020).