Phenolics from grapefruit peels inhibit HMG-CoA reductase and angiotensin-I converting enzyme and show antioxidative properties in endothelial EA.Hy 926 cells

Abstract

This study sought to investigate the possible mechanisms for the use of phenolic extracts from grapefruit peels in the management/ prevention of cardiovascular complications.The effects of the phenolic extracts on key enzymes relevant to cardiovascular diseases [3-hydroxy-methyl-3-glutaryl coenzyme A reductase (HMG-CoA reductase) and angiotensin-I converting enzyme (ACE)], cellular antioxidant activity in human endothelial cells (EA.Hy 926) and radicals [1,1-diphenyl-2 picrylhydrazyl (DPPH) and 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS)] scavenging abilities were investigated. The phenolic contents of the extracts were investigated using HPLC-DAD. There was no significant (P>0.05) difference in the HMG-CoA reductase inhibitory ability of the two extracts, while the bound phenolic extracts had a stronger ACE inhibitory ability than the soluble free phenolics. The extracts also showed intracellular antioxidant activity in human endothelial (EA.hy926) cells. Furthermore, the bound phenolics had significantly higher radicals (DPPH* and ABTS*) scavenging abilities than the free phenolics. The HPLC analysis revealed the presence of flavonoids (quercetin and kaempferol), phenolics acids (resveratrol, gallic acid, ellagic acid and caffeic acid) and tannin (catechin). The cellular antioxidative properties and inhibition of enzymes relevant to the management of cardiovascular complications showed that grapefruit peels could be used as nutraceuticals for the management of such conditions.

Induction of NAD (P)H: Quinone reductase 1 (QR1) and antioxidant activities in vitro of ‘Toranja Burarama’ (Citrus maxima [Burm.] Merr.)

“…These results are potentially important because they imply that toranja peels are a greater source of antioxidants than the interior section (juice), which is in agreement with other studies (Ademosun et al, ; Toh et al, ). And also indicated is that the compounds involved in defense reactions of the citrus fruit are found in greater amounts in the superficial layer; therefore, the antioxidant activity should be related to the part in the fruit where protection against lipid oxidation is needed.…”

“…Quercetin was used as a reference in the assays because it represents one of the major phenolic compounds found in citrus peels (Ademosun et al, ), and it has been reported that it can modulate Phase II metabolism inducing QR (Chen & Blumberg, ). Quercetin inhibited DPPH by 69.7 ± 2.59% at the minimum concentration tested (0.001 mM).…”

“…a Induction ratio was determined by calculating the average specific activity versus specific activity of the control. (Ademosun et al, 2015), and it has been reported that it can modulate Phase II metabolism inducing QR (Chen & Blumberg, 2008). Quercetin inhibited DPPH by 69.7 ± 2.59% at the minimum concentration tested (0.001 mM).…”

“…The antioxidant potential of Citrus was already evaluated by several studies (Ademosun et al, 2015;Castro-Vasquez et al, 2016;Dulay & De Castro, 2016;Guimarães et al, 2010;Jayaprakasha et al, 2008a;Jayaprakasha et al, 2008b;Kelebek, 2010;Klangpetch, Phromsurin, Hannarong, Wichaphon, & Rungchang, 2016), but no study was performed with the different extracts obtained from the new C. maxima.…”

“…Recent reviews have focused on the benefits provided for human health by the fruits of the genus Citrus (Ademosun et al, ; Castro‐Vasquez et al, ). These plants are economically important and a source of bioactive compounds.…”