Abstract
Background and aims:Aframomum melegueta (A. melegueta) from the ginger family is appreciated for its pungent seeds widely used in African ethno-medicine. Among the several biological activities associated with the seed's preparations, some preclinical studies suggest a set of neuroactive properties that have not been tested in humans to date. We performed a clinical trial to investigate the effects of A. melegueta seed extracts on anxiety, stress, mood, and sleep in healthy subjects with moderate anxiety levels. In vitro pharmacological assays targeting the endocannabinoid, serotoninergic, and GABAergic systems were conducted to elucidate the underlying mechanism of action. Methods:A. melegueta standardized to 10% total vanilloids (primarily 6-gingerol, 6-shogaol, and 6-paradol) was obtained after hydroalcoholic extraction and the spray-drying microencapsulation process. Subjects consumed 50, 100, or 150 mg of the extract daily for two days. A set of validated psychometric test questionnaires was collected before and 48 h after the first intake. A. melegueta extract interaction with canonical endocannabinoid receptors (hCB1R and hCB2R), the serotonin receptor (5HT1AR) and gamma-aminobutyric acid receptor (GABAA1R) was evaluated by the radioligand binding assay. Additionally, receptor functional assays and enzyme inhibition assays were conducted to test the extract's functional activity on the non-canonical endocannabinoid receptor (TRPV1) and the cannabinoid fatty-acid amide hydrolase enzyme (FAAH), respectively. Results: In vitro pharmacological tests showed that the A. melegueta extract activated TRPV1, modulated both hCB2R and 5HT1AR and inhibited FAAH, which is the enzyme primarily responsible for hydrolyzing endogenous anandamide. After a 48 h intake period, the extract significantly reduced anxiety and tension related to stress, improved overall mood, and enhanced sleep quality in the participants at doses ranging from 50 to 150 mg, with no reported side effects. Conclusions: This study supports the potential of the A. melegueta extract for anxiety reduction, mood improvement, stress mitigation, and sleep enhancement. The in vitro tests suggest that the extract's primary mechanism of action may involve the inhibition of FAAH, which is a key target in anxiety management.