Phenolic composition and biological prospecting of grains and stems of Retama sphaerocarpa

Retama sphaerocarpa is a shrub widely used in traditional medicine. Owing to the huge demand for bioactive natural components, it is fundamental to study in detail the composition of this kind of plants. In this vein, the phenolic fraction of grains and stems from R. sphaerocarpa grown in Algeria was thoroughly investigated by ultra-high-performance liquid chromatography coupled to mass spectrometry (UHPLC-MS). The extracts obtained by methanol:water (50:50) extraction were also evaluated for their antioxidant and antibacterial activities. The UHPLC-MS analysis allowed the identification of forty two compounds, with twenty one identified in grains and twenty six in stems extracts. Thirty one of these components are referenced for the first time as constituents of R. sphaerocarpa. Stems showed to contain a considerably higher amount of phenolic compounds (11.40 g kg−1 of dry weight). Piscidic acid was identified as the major component, followed by quinic acid and morin/quercetin-di-O-rhamnoside. A taxifolin isomer, isorhamnetin-O-hexoside and an apigenin-6,8-di-C-hexoside isomer were found to be the major phenolic compounds in R. sphaerocarpa grains. The studied samples exhibited moderated antioxidant activities, with stems extract showing the most promising results. This fraction of R. sphaerocarpa also exhibited relevant inhibition against the bacteria Staphylococcus aureus and Pseudomonas aeruginosa. These results are a relevant contribution to the valorization of R. sphaerocarpa as a valuable source of natural bioactive compounds, with recognized nutraceutical applications.