Hippophins C-F, four new flavonoids, acylated with one monoterpenic acid from the seed residue of Hippophae rhamnoides subsp. sinensis

Extract from Sea Buckthorn Seeds-A Phytochemical, Antioxidant, and Hemostasis Study; Effect of Thermal Processing on Its Chemical Content and Biological Activity In Vitro

Sea buckthorn (Hippophae rhamnoides L.) is a small tree, valued for its medicinal properties throughout the ages. Sea buckthorn berries and leaves are a known source of phytochemicals and have been used in the treatment of inflammation, oedema, hypertension, ulcers, and wounds in folk medicine. Sea buckthorn seeds are natural dietary sources of various bioactive compounds as well, but the number of studies on their content and biological properties is still insufficient. For the first time, we examined the phytochemical content and biological activity of sea buckthorn seeds in vitro. We have studied the effect of two extracts-from regular (no thermal processing) and roasted (thermally processed) sea buckthorn seeds-on the levels of oxidative stress induced by H₂O₂/Fe²⁺ in plasma, coagulation times, and white thrombus formation (measured by Total Thrombus-formation Analysis System-T-TAS). We observed that sea buckthorn seeds contain diverse flavonoids, mostly glycosides of isorhamnetin, kaempferol, and quercetin, as well as smaller amounts of proanthocyanidins and catechin, triterpenoid saponins, and a number of unidentified polar and hydrophobic compounds. Both extracts inhibited lipid peroxidation and protein carbonylation, but only the extract from roasted seeds decreased oxidation of thiol groups in plasma treated with H₂O₂/Fe²⁺. They did not alter coagulation times, but the extract from roasted seeds at the highest concentration (50 µg/mL) prolonged the time needed for white thrombus formation. The results indicate that sea buckthorn seeds have antioxidant activity that is not impaired by thermal processing and possess anticoagulant potential, but more research is needed in order to ascertain which compounds are responsible for these effects, especially in in vivo models.

Phytochemistry and pharmacology of sea buckthorn (Elaeagnus rhamnoides; syn. Hippophae rhamnoides): progress from 2010 to 2021

Sea buckthorn (Elaeagnus rhamnoides; syn. Hippophae rhamnoides) is a thorny shrub or a small tree belonging to the Elaeagnaceae family, native to Eurasia. Sea buckthorn fruit is rich in vitamins and minerals, oils from the seeds and fruit flesh find use in medicine and the cosmetic industry or as nutraceutical supplements. Fruit, leaves and other parts of buckthorn have been used in traditional medicine, especially in China, Tibet, Mongolia, and Central Asia countries, and are a rich source of many bioactive substances. Due to its health-promoting and medicinal properties, the plant has been extensively investigated for several decades, and its phytochemical composition and pharmacological properties are well characterized. The years 2010-2021 brought significant progress in phytochemical research on sea buckthorn. Dozens of new compounds, mainly phenolics, were isolated from this plant. Numerous pharmacological studies were also performed, investigating diverse aspects of the biological activity of different extracts and natural products from sea buckthorn. This review focuses on the progress in research on sea buckthorn specialized metabolites made in this period. Pharmacological studies on sea buckthorn are also discussed. In addition, biosynthetic pathways of the main groups of these compounds have been shortly described.