Biological functions of a synthetic compound, octadeca-9,12-dienyl-3,4,5-hydroxybenzoate, from gallic acid–linoleic acid ester

Inhibitory effects of propyl gallate on tyrosinase and its application in controlling pericarp browning of harvested longan fruits

Tyrosinase (EC 1.14.18.1), also known as polyphenol oxidase (PPO), is a key enzyme in pigment biosynthesis of organisms. The inhibitory effects of propyl gallate on the activity of mushroom tyrosinase and effects of propyl gallate on pericarp browning of harvested longan fruits in relation to phenolic metabolism were investigated. The results showed that propyl gallate could potently inhibit diphenolase activity of tyrosinase. The inhibitor concentration leading to 50% activity lost (IC50) was determined to be 0.685 mM. Kinetic analyses showed that propyl gallate was a reversible and mixed type inhibitor on this enzyme. The inhibition constants (K(IS) and K(I)) were determined to be 2.135 and 0.661 mM, respectively. Furthermore, the results also showed that propyl gallate treatment inhibited activities of PPO and POD in pericarp of harvested longan fruits, and maintained higher contents of total phenol and flavonoid of longan pericarp. Moreover, propyl gallate treatment also delayed the increases of browning index and browning degree in pericarp of harvested longan fruits. Therefore, application of propyl gallate may be a promising method for inhibiting tyrosinase activity, controlling pericarp browning, and extending shelf life of harvested longan fruits.

Effect of dietary supplementation of the combination of gallic and linoleic Acid in thigh meat of broilers

This study was performed to investigate the combined effect of dietary supplementation of gallic and linoleic acid (GL) on the antioxidative effect and quality of thigh meat from broilers. Broilers received 3 dietary treatments: i) commercial finisher diet (control), ii) 0.5% GL (gallic:linoleic acid = 1 M:1 M), and iii) 1.0% GL during the 22 to 36 d. The pH value of broiler thigh meat was increased by GL supplementation. Water holding capacity of the thigh meat was enhanced by the 1.0% dietary GL supplementation. Antioxidative effect (total phenolic content, DPPH radical scavenging activity, ABTS(+) reducing activity, reducing power, and TBARS value) in the thigh from the broilers improved significantly with 1.0% GL. Linoleic acid and docosahexaenoic acids were higher in the broilers fed both levels of dietary GL. However, volatile basic nitrogen content and microbiological quality was not shown to be different between control and treated group. Results indicate that 1.0% dietary supplementation of GL can improve the antioxidant activity of broiler thigh meat and may enhance the meat quality.

Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications

OBJECTIVES

To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays.

METHODS

Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2'-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated.

KEY FINDINGS

  The covalent functionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1±0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications.

CONCLUSIONS

For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol.