Angiotensin I-converting enzyme (ACE) inhibitory activity of Fucus spiralis macroalgae and influence of the extracts storage temperature-A short report

Recently, increasing attention has been paid to the marine algae as a natural source of novel angiotensin-I converting enzyme (ACE) inhibitors, such as the phlorotannins that are the predominant polyphenols in brown algae. This study reports, for the first time, the ACE inhibition of methanol extract/fractions from Azorean brown algae Fucus spiralis (Fs) determined by HPLC-UV method, their total phenolic content (TPC) quantified as phloroglucinol equivalents (PE) and the effect of the Fs dry powder methanol extracts (Fs-DME) storage temperature on ACE inhibition. The results indicate that the ACE inhibition of Fs-DME decreased by 28.8% and 78.2% when stored during 15 days at −80 °C and −13 °C, respectively, as compared with the activity of Fs-DME at a refrigerated temperature of 6 °C and assayed immediately after extraction that showed a value of 80.1 ± 2.1%. This Fs-DME sample was fractionated by ultrafiltration membranes into three molecular weight ranges (<1 kDa, 1-3 kDa and >3 kDa), presenting the fraction >3 kDa remarkably high ACE inhibition (88.8 ± 2.4%), TPC value (156.6 ± 1.4 mg PE/g of dry weight fraction) and yield. Furthermore, chromatographic and spectrophotometric analyses corroborate that phenolic compounds were present in Fs methanol extract/fractions, and also revealed that phloroglucinol occurs in Fs. The results seem to suggest that Azorean Fs can be a source of powerful ACE-inhibitory phlorotannins with potential impact on public health, particularly on hypertensive patients.