Extraction of Dietary Bioactive Components from Sea Buckthorn Leaves and Whole Berries using Organic Solvent and Supercritical CO2, and Its Application in the Synthesis of Silver Nano Particles

Abstract

The berries and leaves of Hippophae salicifolia have nutritional and bioactive characteristics, with the leaves being more nutritious and physiologically active than the berries. Vitamin C was the most abundant phytonutrient in the berries, whereas the leaves had the highest total soluble sugar concentration. The berries and mixture of leaves were successively extracted using n-hexane, chloroform, ethyl acetate, acetone, methanol, and water. Total phenolic content (TPC) was highest in the leaves-methanol extract (157.97 ± 2.09 mg GAE/g) and berries-aqueous extract (48.45 ± 1.94 mg GAE/g). Berries-aqueous and leaves-methanol extracts showed excellent global antioxidant scores. Further, extraction of polyphenolic compounds from H. salicifolia leaves using supercritical carbon dioxide (SC-CO2) was optimized to achieve maximum yield of extraction, TPC and antioxidant activity. Under optimized condition. the experimental data showed good agreement with the predicted values. SC-CO2 extraction was more selective for the extraction of ferulic acid, myricetin, and quercetin. SC-CO2 extracts demonstrated notable antibacterial activity. In addition, process variables (pressure, temperature, and CO2 flow rate) for oil extraction from H. salicifolia berries using SC-CO2 were optimized with the objective to achieve maximum oil yield, β-carotene, and total tocopherol contents. CO2 flow rate had a maximum effect on oil yield, while pressure showed a significant influence on β-carotene and total tocopherol contents of oil. The optimum extraction condition was 27.02 MPa pressure, 48.46 °C temperature, 16.45 g/min CO2 flow rate. The oils extracted using solvent and SC-CO2 extraction contained 92.72 and 91.42% UFA. SC-CO2 extracted oil had higher TPC and antioxidant activity than solvent extracted oil. SC-CO2 extracted oil exhibited lower thermal stability and higher resistance to mechanical stress. Finally, silver nanoparticles (Ag NPs) were synthesized using methanol and aqueous extracts of H. salicifolia leaves and berries. Phenolics, proteins, benzenes, and sulforaphane are responsible for converting Ag+ to Ag0. Ag NPs were spherical with an average particle size of 7.87 ± 2.9 nm to 13.86 ± 5 nm. Ag NPs synthesized using aqueous extracts were smaller than those synthesized using methanol. Whereas Ag NPs produced from methanolic extract of leaves exhibited the highest antioxidant and antibacterial activity.