Longan flower water extract promotes sleep in mice via the serotonin-melatonin axis.

BACKGROUND: Longan (Dimocarpus longan) flower is an underutilized botanical byproduct rich in polyphenols with reported neuroprotective actions, yet its role in sleep regulation remains unclear. This study aimed to evaluate the sleep-promoting effects of longan flower water extract (LFWE) and its underlying neurochemical mechanisms in vivo. Although longan flower extract has been suggested to enhance melatonin biosynthesis in vitro, its functional role in sleep modulation remains unclear. RESULTS: High-resolution liquid chromatography-mass spectrometry profiling demonstrated that LFWE is rich in phenolics and flavonoids, with corilagin, gallic acid and epicatechin as dominant constituents, alongside ellagic acid, rutin, procyanidin A2, quercetin and kaempferol. Male C57BL/6 mice received oral LFWE (25 mg kg(-1) d(-1)) for 7 or 14 days. Sleep behavior was assessed in an isoflurane-induced sleep paradigm using loss-of-righting-reflex endpoints. LFWE significantly prolonged total sleep duration after 7 and 14 days relative to vehicle, while sleep latency was unchanged, indicating preferential effects on sleep maintenance rather than initiation. To explore mechanisms, neurotransmitters in brain homogenates and melatonin in plasma were quantified by enzyme-linked immunosorbent assay on day 14. LFWE elevated brain serotonin and dopamine and increased circulating melatonin compared with vehicle. CONCLUSION: Our findings support a mechanistic model in which LFWE augments the serotonin-melatonin axis and modulates monoaminergic tone to enhance sleep maintenance. The combination of water solubility, high polyphenol content and selective prolongation of sleep duration without sedative-like latency reduction highlights LFWE as a safe and sustainable phytochemical resource with translational potential in functional food and nutraceutical applications for sleep regulation. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.