Green tea catechins go nano: study

Chinese researchers report that the chitosan nanoparticles had an encapsulation efficiency of over 50 per cent, according to their findings published in the Journal of Agricultural and Food Chemistry.

“Furthermore, studies on the release profile of tea catechins in vitro demonstrated that the controlled release of tea catechins using chitosan-tripolyphosphate nanoparticles was achievable,”​ wrote lead author Bing Hu from Nanjing Agricultural University.

The technology may extend and enhance the delivery of compounds from green tea, which already have a positive reputation. Previously studies have reported that the compounds may offer protective effects against Alzheimer's and certain cancers, improve cardiovascular and oral health, and play a positive role in weight management.

Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea.

The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).

“Tea catechins have received great attention due to their biological activities, such as antioxidant and antitumour activities,”​ wrote Hu and co-workers. “On the other hand, the oral bioavailability of tea catechins is known to be low, between two and five per cent.”​

To resolve this problem, it is therefore essential to design an effective delivery system for tea catechins,”​ they added

Study details​

Hu and co-workers examined the potential of chitosan-tripolyphosphate (CS-TPP) nanoparticles to encapsulate tea catechins. They found that the particle size and electrostatic charge on the surface of the particles was controlled by the method used to produce the particles.

The researchers formed microgel particles by employing acidic conditions to promote the interaction of NH3 groups in the chitosan with tripolyphosphate (TPP). Optimal encapsulation was achieved when the chitosan was stirred with the tea compounds for 30 minutes before the TPP was added.

Encapsulation was best when they used chitosan with molecular weights between 30 and 150 kDa, but a higher molecular weight chitosan (300 kDa) was inefficient, probably due to steric hindrance, they said.

“It is concluded that the formation of desirable CS-TPP nanoparticles and CS-TPP nanoparticles loaded with tea catechins is possible by controlling the critical fabricating parameters including CS molecular mass, CS concentration, and CS-TPP mass ratio,”​ wrote Hu and co-workers.

Big concerns over a small technology ​

Nanotechnology refers to the control of matter at an atomic or molecular scale of between one and 100 nanometres (nm) - that's one millionth of a millimetre.

Despite still being in its infancy, current estimates on the value of products using nanotechnology put it currently in the range of US$7bn. According to some, the market could be worth as much as $20bn by 2020.

It has already found uses in several industries, including food, nutritional ingredients, and packaging. However, some concerns are surfacing in consumer circles as to the overall safety of the technology.

A recent survey by German food safety authorities, for example, found that 69 per cent of respondents were against the use of nano-additives in spices to prevent them from becoming lumpy; and 84 per cent rejected the idea of making foods look appealing for longer through the use of nanoparticles.

Source: Journal of Agricultural and Food Chemistry​Published online ahead of print, ASAP Article, doi: 10.1021/jf801111c"Optimization of Fabrication Parameters To Produce Chitosan-Tripolyphosphate Nanoparticles for Delivery of Tea Catechins"​Authors: Bing Hu, C. Pan, Y. Sun, Z. Hou, H. Ye, B. Hu, X. Zeng