Autophagy is a ubiquitous and fundamental catabolic vital process for maintaining cellular homeostasis, achieved by degrading and recycling cytoplasmic components, particularly under conditions of nutrient deprivation or metabolic stress. This mechanism is also integral to the selective clearance of misfolded or aggregated proteins, the removal of dysfunctional organelles (such as mitochondria and the endoplasmic reticulum), and the intracellular degradation of pathogens, including those associated with peroxisomes. In this study, we screened and identified sesamin, a bioactive compound isolated from Hypericum hookerianum extracts, as a novel autophagy activator. Our results demonstrated that sesamin effectively induces autophagy and activates the lysosome biogenesis pathway.

Glutamate-mediated oxidative stress causes neuronal cell death by increasing intracellular Ca2+ uptake, reactive oxidative species (ROS) generation, mitogen-activated protein kinase (MAPK) activation, and translocation of apoptosis-inducing factor (AIF) to the nucleus. In the current study, we demonstrated that corydaline exerts potent neuroprotective effects against glutamate-induced neurotoxicity. Treatment with 5 mmol/L glutamate increased cellular Ca2+ influx, ROS generation, MAPK activation, and AIF translocation. In contrast, corydaline treatment decreased cellular Ca2+ influx and ROS generation. Western blot analysis revealed that glutamate-mediated MAPK activation was attenuated by corydaline treatment. We further demonstrated that corydaline treatment inhibited the glutamate-mediated translocation of AIF to the nucleus. We propose that corydaline is a promising lead structure for the development of safe and effective neuroprotectants.

Neuroinflammation is known as the main mechanism implicated in the advancement of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. The main feature of neuroinflammation is associated with the activation of microglia. The activated microglia increase proinflammatory cytokine production and induce progressive neuronal cell death. Citrus flavonoids show neuroprotective effects that are associated with the anti-inflammatory action of flavonoids in neurodegenerative diseases. Among these citrus flavonoids, kaempferol, naringin, and nobiletin show inhibitory effects on nuclear factor-κB and mitogen-activated protein kinase signaling pathways that can modulate inflammatory conditions in microglial cells. In the present review, we present the anti-inflammatory activities of citrus flavonoids and therapeutic potential of flavonoids as neuroprotective agents.