Food & Function Blog

Scientists from Australia and China have reported the Angiotensin Converting Enzyme (ACE) inhibitory activity of a variety of teas (Camellia sinensis) in vitro. ACE is an important enzyme involved in the control of blood pressure, as it transforms angiotensin into angiotensin II, which is a powerful vasoconstrictor. Therapeutic ACE inhibitors are therefore an important class of pharmaceuticals which can be used to control high blood pressure. A variety of food components including polyphenolics, peptides and unsaturated fats have been shown to lower blood pressure via inhibition of ACE.

This study correlates the processing methods used to produce the tea with the observed ACE inhibitory properties. It was found that the polyphenols in green tea (non-oxidized tea) displayed the highest values for ACE inhibition, whereas the polyphenols in black and dark teas (fully-oxidized teas) had the lowest inhibitory activity of the 5 varieties tested. In addition, the ACE inhibition kinetics were explored for the range of teas in order to characterize the mechanism of inhibition. An allosteric (not Michaelis–Menten) mechanism was observed, which implies synergistic subunits within the enzyme or the occurrence of irreversible changes to the enzyme – a mechanism which is common in pharmaceutical ACE inhibitors.

To find out more, read the full article for free by following the link below:

Inhibition of angiotensin converting enzyme (ACE) activity by polyphenols from tea (Camellia sinensis) and links to processing method, Junjie Dong, Xinqing Xu, Yuerong Liang, Richard Head and Louise Bennett, Food Funct., 2011, DOI: 10.1039/C1FO10023H

New research by Food & Function Associate Editor Steven Feng Chen and co-workers describes the protective effects of certain microalgal strains against endogenous and exogenous advanced glycation endproducts (AGEs). AGEs are generated from the glycation between sugars and protein and can lead to the cross-linking of key molecules resulting in functional impairment. AGEs are believed to be important factors associated with the development of diabetic retinopathy – the leading cause of blindness in Western countries.

In this study, the extracts and active compounds of 3 microalgal strains (Chlorella zofingiensis,  Chlorella protothecoides and Nitzschia laevis) were tested for their inhibitory effects on the glycation process in a cell based model. Results showed that astaxanthin, lutein and eicosapentaenoic acid (EPA) isolated from the microalgae reduced cell proliferation and the upregulation of both vascular endothelial growth factor and MMP2 mRNA, which are vital steps in the development of diabetic retinopathy. Therefore, these microalgal species can be regarded as beneficial foods for people suffering from diabetic retinopathy.

To find out more, read the article in full for free by following the link below:

Protective actions of microalgae against endogenous and exogenous advanced glycation endproducts (AGEs) in human retinal pigment epithelial cells
Zheng Sun, Jin Liu, Xiaohui Zeng, Jieqiong Huangfu, Yue Jiang, Mingfu Wang and Feng Chen
Food Funct., 2011, DOI: c1fo10021a

This review from Gow-Chin Yen and co-workers in Taiwan reviews the anti-glycation properties of various foods and their mechanisms of action.  Glycation, also known as the Malliard reaction is a type of nonenzymatic browning involving the reaction of carbohydrate with protein.  It occurs ubiquitously in food, particularly during heating, processing and storage.  It has also been implicated in accelerated aging and diabetic complications in vivo although the molecular basis of this pathogenesis is not well understood.

Most studies to date have focused on the deleterious effects of toxic advanced glycation endproducts (AGEs) and it remains unclear whether phytochemicals, implicated in the reduction of toxic effects in clinical trials, actually exert protective effects against glycotoxin-induced damage.  These natural potential AGE inhibitors may provide a therapeutic approach for delaying and preventing premature aging and diabetic complications.

Interested in knowing more?  Read the full article by following the link below, all content in Food & Function is free to access until the end of 2011.

Inhibition of advanced glycation endproduct formation by foodstuffs
Chi-Hao Wu, Shang-Ming Huang, Jer-An Lin and Gow-Chin Yen
Food Funct., 2011, Advance Article
DOI: 10.1039/C1FO10026B