Context: γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter and it is well established that activation of GABA_A receptors favours sleep. l-Theanine, a naturally occurring amino acid first discovered in green tea, is a well-known anti-anxiety supplement with proven relaxation benefits. Objective: This study investigated the potential synergistic sleep enhancement effect of GABA/l-theanine mixture. Materials and methods: Pentobarbital-induced sleep test was applied to find proper concentration for sleep-promoting effect in ICR mice. Electroencephalogram (EEG) analysis was performed to investigate total sleeping time and sleep quality in normal SD rats and caffeine-induced awareness model. Real-time polymerase chain reaction (RT-PCR) was applied to investigate whether the sleep-promoting mechanism of GABA/l-theanine mixture involved transcriptional processes. Results: GABA/l-theanine mixture (100/20 mg/kg) showed a decrease in sleep latency (20.7 and 14.9%) and an increase in sleep duration (87.3 and 26.8%) compared to GABA or theanine alone. GABA/l-theanine mixture led to a significant increase in rapid eye movement (REM) (99.6%) and non-REM (NREM) (20.6%) compared to controls. The use of GABA/l-theanine mixture rather than GABA or l-theanine alone restored to normal levels sleep time and quality in the arousal animal model. The administration of GABA/l-theanine led to increased expression of GABA and the glutamate GluN1 receptor subunit. Conclusions: GABA/l-theanine mixture has a positive synergistic effect on sleep quality and duration as compared to the GABA or l-theanine alone. The increase in GABA receptor and GluN1 expression is attributed to the potential neuromodulatory properties of GABA/l-theanine combination, which seems to affect sleep behaviour.

The objective of this study was to evaluate the anti-aging potential and skin safety of red ginseng (RG) and fermented red ginseng (FRG) using Lactobacillus brevis for use as cosmetic ingredients. Concentrations of uronic acid, polyphenols, and flavonoids, and antioxidant activities were greater in FRG compared to RG. The contents of total ginsenosides were not significantly different. However, the ginsenoside metabolite content was higher in FRG (14,914.3 μg/mL) compared to RG (5697.9 μg/mL). The tyrosinase inhibitory activity (IC₅₀) of FRG was 27.63 μg/mL, and more potent compared with RG (34.14 μg/mL), (P<.05). The elastase inhibitory activity (IC₅₀) of FRG was 117.07 μg/mL also higher compared with RG (157.90 μg/mL). In a primary skin irritation test, 10% RG and 10% FRG were classified as practically nonirritating materials. In a skin sensitization test, the RG group showed a sensitization rate of 100% and its mean evaluation score of irritation was 1.4, whereas the FRG group showed 20% and 0.2%, respectively. By fermentation of RG, FRG has increased contents of ginsenoside metabolites, such as Rg3, Rg5, Rk1, compound K, Rh1, F2, Rg2, and flavonoids content. Therefore, FRG offers increased anti-wrinkle efficacy, whitening efficacy, and reduced toxicological potency compared to RG.