Quality assessment of flavonoids and polyphenolic compounds in green tea samples belonging to different origins

Components of green tea (Camellia sinensis) have been of considerable interest in recent years because of their potential utility as pharmaceutical agents [1]. So a comprehensive approach was adopted to carry out analysis for the quality assessment of flavonoids in tea samples belonging to different origins.

For this purpose extraction, thermal decomposition investigations, separation and mass spectrometric detection parameters were optimized. Extraction methods tried so far include, reflux extraction, a modified accelerated solvent extraction (ASE) namely aquasolve extraction [2] and microwave assisted extraction [3] (MAE). For separation a HPLC method using different C18 stationary phases was established. In this coherence, the influence of material itself i.e. monolithic silica (Chromolith, Merck) and silica particles (Prontosil, Bischoff) was studied. HPLC-DAD (diode array detector) and HPLC-ESI-MS (electrospray ionization mass spectrometry) were used for simultaneous detection, rendering MS more reliable owing to high specificity and sensitivity.

Results clearly demonstrated MAE in 50% ethanol to be best extraction method giving highest yields in shortest possible time. Thermal decomposition studies for two standards, quercetin and gallic acid revealed that approx. 20% of quercetin in aquasolve method is lost. Additionally aquasolve extraction showed high degree of epimerization [4] as compared to MAE, but it did not accompany the complete conversion of green tea epicatechins (GTE) to their corresponding epimers. Rather some irreversible degradation phenomenon was also involved. Optimized separation system was finally used for qualitative and quantitative investigation of catechin derivatives, oligomers and polymers, from different green tea samples. Within this approach a correlation to high quality products could be noticed.

Refrences: 1. Harborne, J.B. (1998), Phytochemical Methods, Chapman & Hall, London. 2. Bonn, G., Hörmeyer, H.F., Bobleter, O. (1987), Wood Science and Technology 21: 179–185. 3. Pan, X. (2003), Chemical Engineering and Processing 42: 129–133. 4. Jin Ze Xu, (2003), Sci. Food Agric. 83: 1617–1621.