Gallic acid isolated from Spirogyra sp. improves cardiovascular disease through a vasorelaxant and antihypertensive effect

- GA, a strong antioxidant isolated from Spirogyra sp., possesses vasorelaxant effect in HUVECs.
- GA inhibits angiotensin I converting enzyme (ACE) and administration of GA reduces the blood pressure in SHRs.
- GA exerts multiple therapeutic effects on CVDs related to vasorelaxant and antihypertensive effect.

In this study, we investigated the vasorelaxant and antihypertensive effects of gallic acid (GA), a polyphenol isolated from the green alga Spirogyra sp., to assess its suitability as a therapeutic for cardiovascular diseases (CVDs). We examined the effect of GA on endothelium-dependent vasorelaxation in human umbilical vein endothelial cells (HUVECs). GA increased nitric oxide (NO) levels by increasing phosphorylation of endothelial nitric oxide synthase (eNOS), and its effect on NO production was attenuated by pretreatment with the eNOS inhibitor NG-nitro-l-arginine methyl ester (l-NAME). We also investigated its antihypertensive effect by examining GA-mediated inhibition of angiotensin-I converting enzyme (ACE). GA inhibited ACE with a half-maximal inhibitory concentration (IC50) value of 37.38 ± 0.39 μg/ml. In silico simulations revealed that GA binds to the active site of ACE (PDB: 1O86) with a binding energy of −270.487 kcal/mol. Furthermore, GA clearly reduced blood pressure in spontaneously hypertensive rats (SHR) to an extent comparable to captopril. These results suggest that GA isolated from Spirogyra sp. exerts multiple therapeutic effects and has potential as a CVD treatment.