Quercetin is one of the most common, naturally occurring flavonoids, structurally classified to the flavonol subfamily. This compound, found in many edible and medicinal plants either as a free or glycosidated form, has been scientifically exploited for many years, and one could hardly expect it could be a hero of some additional story. Commonly recognized as an anti-inflammatory agent, quercetin not only limits capillary vessel permeability by inhibiting hyaluronidase but also blocks cyclooxygenases and lipoxygenases. As a typical flavonoid, it is also known for its antioxidant effect, which was confirmed by many in vitro and in vivo studies. Throughout the years, numerous other activities were reported for quercetin, including antidiabetic, anti-proliferative, or anti-viral. Of note, recent data have revealed its potential role as a therapeutic agent for several central nervous system disorders. This review provides an overview of available experimental data on quercetin and its complexes with respect to central nervous system diseases, with a main focus on some aspects that were not discussed previously, such as anti-anxiolytic effects, anti-Huntington’s disease activity, or therapeutic potential in brain cancer. Moreover, quercetin’s protective role in some of these diseases is discussed, especially as an anti-neuroinflammatory agent. Bearing in mind the poor bioavailability of this compound, possible options that would enhance its delivery to the site of action are also presented.

Introduction: Adaptogens are a group of plants that exhibit complex, nonspecific effects on the human body, increasing its ability to adapt, develop resilience, and survive in stress conditions. They are found in many traditional medicinal systems and play a key role in restoring the body’s strength and stamina. Research in recent years has attempted to elucidate the mechanisms behind their pharmacological effects, but it appears that these effects are difficult to define precisely and involve multiple molecular pathways. Neuroinflammation: In recent years, chronic inflammation has been recognized as one of the common features of many central nervous system disorders (dementia and other neurodegenerative diseases, depression, anxiety, ischemic stroke, and infections). Because of the specific nature of the brain, this process is called neuroinflammation, and its suppression can result in an improvement of patients’ condition and may promote their recovery. Adaptogens as anti-inflammatory agents: As has been discovered, adaptogens display anti-inflammatory effects, which suggests that their application may be broader than previously thought. They regulate gene expression of anti- and proinflammatory cytokines (prostaglandins, leukotriens) and can modulate signaling pathways (e.g., NF-κB). Aim: This mini-review aims to present the anti-neuroinflammatory potential of the most important plants classified as adaptogens: Schisandra chinensis, Eleutherococcus senticosus, Rhodiola rosea and Withania somnifera.

Steroidal saponins are a group of glycosides widely distributed among monocotyledonous families. They exert a wide spectrum of biological effects including cytotoxic and antitumor properties which are the most studied. This review is an update of our previous paper—Saponins as cytotoxic agents(Podolak et al. in Phytochem Rev 9:425–474, 2010) and covers studies that were since published (2010–2018). In this paper we refer to steroidal saponins presenting results of cytotoxicity studies, mechanisms of action and structure–activity relationships.

Genipin is a non-glycosidic iridoid isolated mainly from the fruits of Gardenia jasminoides and Genipa americana. It is the active ingredient in extracts from these plants, responsible for their anti-inflammatory and hepatoprotective effects. In several in vitro tests, its anti-proliferative activity against tumour cell lines has been demonstrated, and due to its ability to specifically inhibit the UCP2 protein and inhibit STAT3 activation, a significant increase in the cytotoxicity of several anticancer drugs was observed in co-treatment with genipin. In recent years, the importance of genipin has increased due to the possibility of using this iridoid as a biocompatible and low cytotoxicity potent crosslinking agent in the manufacture of dressings, in tissue engineering, as a component of a drug carrier system and in the production of food packaging. Genipin is also a substrate in the production of a blue pigment used as a food additive and fabric pigment, and other applications. Due to documented cases of hepatotoxicity, genipin and the blue pigment derived from it are being investigated for effective and safe therapeutic and non-drug use. The current paper discusses selected aspects of chemistry, activity and use of this interesting compound.