Tunisian Silybum species: Potential source of phytochemicals, organic acids, minerals, and proteins across various plant organs

Abstract

Abstract The genus Silybum comprises two closely related species, S. marianum and S. eburneum, both of which are listed among the most highly valued wild edible plants. Various local rural communities in the Mediterranean basin have incorporated these plants into their diets. In this study, we investigated the organs (stems, leaves, flowers, immature seeds, and mature seeds) of wild, potassium, edible S. marianum and S. eburneum collected from two Tunisian regions for their mineral composition, polyphenolic contents, organic acids, seed storage proteins, as well as their antioxidant potential. The Flame atomic spectroscopy revealed that, in S. marianum, stems had high sodium, while potassium and calcium were in the flower and leaf. S. eburneum had high sodium in stems and potassium and calcium in the flower, with variations in magnesium and other minerals. S. marianum shows substantial fructose variation among its organs, with the highest content in the stem (3.54 mg/g DW) and the lowest in immature seeds (0.01 mg/g DW). Conversely, S. eburneum exhibits significant heterogeneity in glucose, sucrose, and maltose levels across its organs, with maltose exclusively detected in immature seeds. A notable organ-dependent distribution of organic acids was observed for oxalic, quinic, citric, malic, succinic, lactic, formic, acetic, and propionic acids among the two species. The phenolic contents were calorimetrically evaluated and further submitted to an LC-MS analysis. Higher levels were detected in both mature and immature seeds in both species compared to the other plant parts. Also, the seeds possessed higher antioxidant activities. A total of 32 phenolics were identified with 3,4-di-O-caffeoyquinic acid, 4,5-di-O-caffeoyquinic acid, syringic acid, protocatechuic acid, naringenin, apigenin, and quercetin were detected as the dominant compounds. In both S. marianum and S. eburneum, albumins and globulins are the predominant protein fractions in both mature and immature seeds and the storage protein fraction was mostly affected by the maturity stage. This current study substantiates the versatile utility of Silybum as a sustainable resource with significant potential for its nutritional applications in the production of functional foods across diverse sectors of the food industry.