Hydroethanolic
Cucurbita pepo seed extracts are traditionally used for alleviating lower urinary tract symptoms (LUTS), yet their mechanisms remain unclear. Adenosine, a purine nucleoside involved in neuromodulation and smooth muscle relaxation, was recently identified in
C. pepo seeds. Since A
1 adenosine receptors
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Hydroethanolic
Cucurbita pepo seed extracts are traditionally used for alleviating lower urinary tract symptoms (LUTS), yet their mechanisms remain unclear. Adenosine, a purine nucleoside involved in neuromodulation and smooth muscle relaxation, was recently identified in
C. pepo seeds. Since A
1 adenosine receptors (A
1AR) suppress parasympathetic bladder overactivity by inhibiting acetylcholine (ACh) release, we investigated to which extent purines from pumpkin seed extracts contribute to A
1AR activation. Complementary antioxidant capacity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Three hydrophilic seed extracts containing different adenosine levels (0.60–1.18 mg/g dw) were evaluated for agonist activity using a cAMP inhibition assay. The most active extract showed an EC
50 of 40.22 µg/mL. Selective removal of adenosine shifted the dose–response curve rightward, while further elimination of an adenosine derivative increased the EC
50 to 212.10 µg/mL, confirming adenosine as the principal active compound. Guanosine and inosine did not exhibit A
1AR agonist or allosteric effects. All samples exhibited measurable but weak antioxidant activity (IC
50 = 1.02–4.19 mg/mL), consistent with their low total phenolic content. These findings underscore the importance of accounting for naturally occurring agonists in plant extracts to avoid overestimating receptor-mediated effects in vitro which are not translatable in vivo.
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