Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of anti-cancer drugs. The main symptoms often include sensory disturbances and neuropathic pain, and currently there is no effective treatment for this condition. This study aimed to investigate the suppressive effects of magnolin, an extracellular signal-regulated kinase (ERK) inhibitor substance derived from a 95% EtOH extract of the seeds of Magnolia denudata, on the symptoms of CIPN. A taxol-based anti-cancer drug paclitaxel (PTX) was repeatedly injected (2 mg/kg/day, total 8 mg/kg) into mice to induce CIPN. A neuropathic pain symptom was assessed using a cold allodynia test that scores behaviors of licking and shaking paw after plantar administration of acetone drop. Magnolin was administered intraperitoneally (0.1, 1, or 10 mg/kg) and behavioral changes to acetone drop were measured. The effect of magnolin administration on ERK expression in the dorsal root ganglion (DRG) was investigated using western blot analysis. The results showed that the repeated injections of PTX induced cold allodynia in mice. Magnolin administration exerted an analgesic effect on the PTX-induced cold allodynia and inhibited the ERK phosphorylation in the DRG. These results suggest that magnolin could be developed as an alternative treatment to suppress paclitaxel-induced neuropathic pain symptoms.

Neuroinflammation, predominantly mediated by microglial activation, is a key immunological response in the pathogenesis of neurodegenerative disorders. In our preliminary study, the aerial part of Artemisia iwayomogi inhibits LPS-induced microglial activation. The present study aims to identify chemical constituents with anti-neuroinflammatory properties in the aerial parts of A. iwayomogi. Two new guaianolide sesquiterpenes, iwayomogins A and B (1 and 2), along with thirteen known sesquiterpene lactones (3–15), one diterpene glycoside (16), and nine phenolic compounds (17–25) were isolated from the aerial parts of A. iwayomogi by repeated chromatography. The structures of the isolates were elucidated by their spectroscopic data. All isolates were evaluated for their inhibitory activities on nitric oxide (NO) production in LPS-induced BV-2 microglial cells. 2,3-Dehydro-1-epi-asperilin (11) exhibited the strongest inhibitory effect on NO production (IC₅₀ value of 1.78 μM). In the molecular docking study, three compounds (1, 2, and 11) showed good binding affinities with iNOS. Additionally, compounds 1, 2, and 11 inhibit pro-inflammatory cytokines (TNF-α and IL-6) in dose-dependent manners. The present study demonstrates that the chemical constituents from A. iwayomogi inhibit NO production and pro-inflammatory cytokine release in BV-2 cells. However, further evaluation with biological experiments utilizing in vivo models is necessary.

Oxidative catabolism of monoamine neurotransmitters by monoamine oxidases (MAOs) produces reactive oxygen species (ROS), which contributes to neuronal cells’ death and also lowers monoamine neurotransmitter levels. In addition, acetylcholinesterase activity and neuroinflammation are involved in neurodegenerative diseases. Herein, we aim to achieve a multifunctional agent that inhibits the oxidative catabolism of monoamine neurotransmitters and, hence, the detrimental production of ROS while enhancing neurotransmitter levels. Such a multifunctional agent might also inhibit acetylcholinesterase and neuroinflammation. To meet this end goal, a series of aminoalkyl derivatives of analogs of the natural product hispidol were designed, synthesized, and evaluated against both monoamine oxidase-A (MAO-A) and monoamine oxidase-B (MAO-B). Promising MAO inhibitors were further checked for the inhibition of acetylcholinesterase and neuroinflammation. Among them, compounds 3aa and 3bc were identified as potential multifunctional molecules eliciting submicromolar selective MAO-B inhibition, low-micromolar AChE inhibition, and the inhibition of microglial PGE₂ production. An evaluation of their effects on memory and cognitive impairments using a passive avoidance test confirmed the in vivo activity of compound 3bc, which showed comparable activity to donepezil. In silico molecular docking provided insights into the MAO and acetylcholinesterase inhibitory activities of compounds 3aa and 3bc. These findings suggest compound 3bc as a potential lead for the further development of agents against neurodegenerative diseases.