Neurodegenerative diseases, namely Alzheimer's disease and Parkinson's disease represent a deleterious impact worldwide. Despite extensive preclinical and clinical research in neurodegenerative disorders, therapeutic strategies aimed at the prevention and chronic treatment of neurodegenerative conditions have not been successfully translated to the clinic. Therefore, the identification of novel pharmacological intervention derived from natural products is warranted. Nobiletin and tangeretin are important citrus flavonoids derived from the peel and other parts of Citrus L. genus, and have been shown to exhibit neuroprotective effects in several in vitro and in vivo studies. Apart from there antioxidant and anti-inflammatory effects, nobiletin and tangeretin have been shown to attenuate cholinergic deficits, reduce the abnormal accumulation of neurotoxic amyloid-beta peptides, reverse N-methyl- D-aspartate (NMDA) receptor hypofunction, ameliorate ischemic injury, inhibit hyperphosphorylation of tau protein, enhance neprilysin levels, modulate several signaling cascades, and protect against 1-methyl-4-phenylpyridinium (MPP(+)) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity. Taken together, these naturally occurring phytochemicals may represent beneficial drug candidates for the treatment and prevention of Alzheimer's and Parkinson's disease.

Dihydrochalcones are a class of secondary metabolites, whose demand in biological and pharmacological applications is rapidly growing. Phloretin is one of the best known and abundant dihydrochalcone characterized by the presence of 2,6-dihydroxyacetophenone pharmacophore. It is a versatile molecule with anticancer, antiosteoclastogenic, antifungal, antiviral, anti-inflammatory, antibacterial and estrogenic activities and able to increase the fluidity of biological membranes and penetration of administered drugs. In this review we have performed a critical evaluation of available literature as far as phloretin beneficial effects and activation/block of intracellular signal cascade are of concern. In addition, we supply useful information on its chemical properties, sources and bioavailability.

Background Over the last two decades there has been a substantial increase of the number of studies on the species of genus Sideritis. Species of section Empedoclia, occurring in the Eastern Mediterranean region and in part of Western Asia possess some remarkable characteristics and are known as valuable medicinal plants used by local people in the traditional medicine and for herbal tea. The objective of the review is to make a survey on the recent studies on the ethnopharmacology and biological activity of the species in Southeastern Europe and in Turkey, which is the center of distribution and their main occurrence. Main body The review focuses on the ethnopharmacology and biological activities of the species of interest. The survey revealed that a total of 47 species belonging to section Empedoclia have been studied either in ethnopharmacological aspect, or in relation to their biological activities, or both. Most species have been used traditionally by the local people as herbal tea or for treatment of various health problems, most frequently flu, cold and respiratory diseases. Sideritis species demonstrate numerous biological activities and are promising for use in the therapy of many diseases and health disorders. Antioxidant activity was found in 40 species, antimicrobial and antibacterial activityin 27 species, anti-inflammatoryin 14 species, antifungalin 8 species, cytotoxicin 7 species. There were also some other, more specific biological activities, found in a few species, but considered promising for further studies and application. Short conclusion The species of genus Sideritis, section Empedoclia have been used by local people as herbal tea and in traditional medicine since long time ago. People are taking advantage of the high species diversity and are aware of their useful properties. Much more information is available on the biological activities of the target species than on their traditional uses. Most species demonstrate various biological activities and are of substantial interest for further studies on their pharmacological properties and their potential for pharmacy and medicine.

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