Nanotechnology is a science that has developed rapidly in recent years and has a wide range of applications . Nanoparticles are basic building blocks with different properties due to their large surface area/volume ratio. In recent years, nanoparticles have formed the basis of modern materials science . Silver nanoparticles (AgNPs) gain great interest in biology, biomedical, drug delivery, medicine, agriculture, food industries, textile industries, and electronics .
Several synthetic routes have been developed to produce AgNPs including electrochemical, radiation technique , and photochemical . However, these methods lead to environmental contamination, toxic residue, and high cost. Therefore, natural products gain great interest in the synthesis of nanoparticles due to their eco-friendly, low cost, high efficiency, and scale-up properties [6, 7].
Natural products such as plant extract, microorganisms, algae, oilcake, vegetable waste, seaweed, enzymes, arthropods have been used for the production of AgNPs. It has been accepted that plant-based materials are the promising substrate for the AgNPs synthesis due to the corresponding advantages . The biological effects of AgNPs depend on some crucial factors such as surface chemistry, size, shape, particle morphology, particle composition, coating/capping, agglomeration, and dissolution rate, particle reactivity in solution, the efficiency of ion release, cell type, the type of reducing agent . AgNPs synthesised from plants were reported to show significant biological activities such as antioxidant , antibacterial , anticancer [12, 13], antifungal , antiviral , anti-inflammatory .
Silver nanoparticles were synthesised from Salvia leucantha that revealed considerable antibacterial activity . Salvia officinalis is well known of Salvia genus. Silver nanoparticles synthesised from S. officinalis was reported to display significant antibacterial , antiplasmodial , antioxidant and anti-inflammatory , antileishmanial effects .
Free radicals are called reactive oxygen species including hydroxyl (OH•), peroxyl (ROO•), superoxide (O2•), peroxinitrite (•ONOO−) radicals that were produced throughout oxidation within the mammalian body . The human body has many protection systems against oxidative stress. The natural antioxidants become insufficient in some situations and then, the excess radicals can damage to cell membrane resulting in diseases . Therefore, food including antioxidants should be consumed to cope with this situation. An antioxidant is defined as a substance that inhibits the oxidation of the substrate . Accordingly, phenolic compounds are produced from the secondary metabolism of plants and are considered natural antioxidants because they protect many organs from oxidation . There has been an increase in the use of natural antioxidants due to the benefits provided by the aromatic herbs of extracts, essential oils, and spices . Herbal-based products contain phenolic phytochemicals, one of the most powerful antioxidants, and contribute to body defense against oxidative damage. These compounds protect against deterioration and provide antioxidant substances to the human body because of their consumption[27–29].
Salvia L. species have been used since ancient times due to their antioxidant, natural preservative, spice, aromatic substance, and medicinal properties . Salvia is an important genus belonging to the Lamiaceae (formerly Labiatae) family. Around the world, 1000 species of Salvia are used as herbal tea and flavoring, as well as in the cosmetics and pharmaceutical industries. Salvia species have been used in the treatment of colds, coughs, toothache, gastrointestinal problems, coronary heart disease, hepatochirosis, hepatitis, cerebrovascular disease, chronic renal failure, dysmenorrhea, and neurasthenic insomnia as traditional medicine . In addition, Salvia herbs are known to have a wide variety of pharmacological activities such as antimicrobial, antioxidant, anti-inflammatory, anticancer, hypoglycemic, hypolipidemic, antinociceptive, memory-enhancing effects. Salvia genus is rich in polyphenols, especially phenolic acid, and flavonoids [32, 33].
In this study, Salvia aethiopis mediated synthesis of silver nanoparticles was achieved and antioxidant activity of corresponding Sa-AgNPs was carried out.