Search

Chemical variation of Silybum marianum growing in the north, middle, and south of Egypt was investigated. Variation was assessed according to the content of the individual silymarin components in the fruits of the plant. The fruits were distinguished according to location, plant variety, and fruit color (maturity). Accelerated solvent extraction was used to standardize the silymarin extraction. Quantitative analysis of the content of silymarin components was carried out using HPLC with qNMR-controlled reference standards of taxifolin and seven major flavonolignans including silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, and silydianin. The quantification method was validated in accordance with ICH guidelines. Principal component analysis and hierarchical clustering were carried out to create homogeneous clusters of samples based on the content of the silymarin components. Taxifolin had the lowest correlation relative to other silymarin components, whereas silybin A was positively correlated with silybin B. The samples clustered into three classes: silydianin-rich samples, samples with an average silymarin content of <18.8 mg/g, and one class enriched in silymarin (>18.8 mg/g). S . marianum growing in the Nile delta showed the highest silymarin content. No correlation was found between fruit color and silymarin content, indicating that the fruit maturity stage has no significance. [ABSTRACT FROM AUTHOR]

Flavonolignans constitute an important class of plant secondary metabolites formed by oxidative coupling of one flavonoid and one phenylpropanoid moiety. The standardized flavonolignan-rich extract prepared from the fruits of Silybum marianum is known as silymarin and has long been used medicinally, prominently as an antihepatotoxic and as a chemopreventive agent. Principal component analysis of the variation in flavonolignan content in S. marianum samples collected from different locations in Egypt revealed biosynthetic relationships between the flavonolignans. Silybin A, silybin B, and silychristin are positively correlated as are silydianin, isosilychristin, and isosilybin B. The detection of silyamandin in the extracts of S. marianum correlates with isosilychristin and silydianin content. The positive correlation between silydianin, isosilychristin, and silyamandin was demonstrated using quantitative 1 H nuclear magnetic resonance spectroscopy (qHNMR). These correlations can be interpreted as evidence for the involvement of a flavonoid radical in the biosynthesis of the flavonolignans in S. marianum. The predominance of silybins A & B over isosilybin A & B in the silybin-rich samples is discussed in light of the relative stabilities of their respective radical flavonoid biosynthetic intermediates., (Copyright © 2017 Elsevier B.V. All rights reserved.)