Review of the therapeutic potential of Forsythiae Fructus on the central nervous system: Active ingredients and mechanisms of action

Traditional Chinese medicine has gained significant attention in recent years owing to its multi-component, multi-target, and multi-pathway advantages in treating various diseases. Forsythiae Fructus, derived from the dried fruit of Forsythia suspensa (Thunb.) Vahl, is one such traditional Chinese medicine with numerous in vivo and ex vivo therapeutic effects, including anti-inflammatory, antibacterial, and antiviral properties. Forsythiae Fructus contains more than 200 chemical constituents, with forsythiaside, forsythiaside A, forsythiaside B, isoforsythiaside, forsythin, and phillyrin being the most active ingredients. Forsythiae Fructus exerts neuroprotective effects by modulating various pathways, including oxidative stress, anti-inflammation, NF-κB signaling, 2-AG, Nrf2 signaling, acetylcholinesterase, PI3K-Akt signaling, ferroptosis, gut-brain axis, TLR4 signaling, endoplasmic reticulum stress, PI3K/Akt/mTOR signaling, and PPARγ signaling pathway. This review aims to highlight the potential therapeutic effects of Forsythiae Fructus on the central nervous system and summarize the current knowledge on the active ingredients of Forsythia Fructus and their effects on different pathways involved in neuroprotection. In this review, we conducted a comprehensive search of databases (PubMed, Google Scholar, Web of Science, China Knowledge Resource Integrated, local dissertations and books) up until June 2023 using key terms such as forsythia suspensa, Forsythiae Fructus, forsythiaside, isoforsythiaside, forsythin, phillyrin, Alzheimer′s disease, Parkinson's disease, ischemic stroke, intracerebral hemorrhage, traumatic brain injury, aging, and herpes simplex virus encephalitis. Our findings indicate that Forsythiae Fructus and its active ingredients own therapeutic effects on the central nervous system by modulating various pathways, including oxidative stress, anti-inflammation, NF-κB signaling, 2-AG, Nrf2 signaling, acetylcholinesterase, PI3K-Akt signaling, ferroptosis, the gut-brain axis, TLR4 signaling, endoplasmic reticulum stress, PI3K/Akt/mTOR signaling, and PPARγ signaling pathway. Forsythiae Fructus and its active ingredients have demonstrated promising neuroprotective properties. Future in vivo and clinical studies of Forsythiae Fructus and its active ingredients should be conducted to establish precise dosage and standard guidelines for a more effective application in the treatment of neurological disorders.