White and green tea polyphenols inhibit pancreatic lipase in vitro

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Abstract

Green, white and black teas were assayed for inhibition of pancreatic lipase activity in vitro. White tea proved to be more effective than green tea with black tea showing little inhibition even at 200 μg GAE/ml. The EC50 values for inhibition were 22 μg/ml for white tea and 35 μg/ml for green tea; both easily achievable from normal infusions of tea. Liquid chromatography-mass spectroscopy analysis showed that white and green teas had essentially equal amounts of flavan-3-ols but green tea had higher levels of flavonols. White tea had higher levels of 5-galloyl quinic acid, digalloyl glucose, trigalloyl glucose and the tannin, strictinin.

After chromatography on Sephadex LH-20, the main inhibitory fraction was enriched in strictinin and fractions enriched in other components were ineffective. This suggests that strictinin content may be crucial for inhibition of pancreatic lipase. However, the possibility of synergies between the polyphenols cannot be disregarded.

Introduction

Tea is often quoted as being the most commonly consumed beverage in the world other than water. The majority of commercial teas arise from dried leaf material from Camellia sinensis L and a wide range of different teas can be produced. The main consumed types are black and green tea but recently white tea has become more available to consumers in the West. These teas mainly differ in their degree of processing but white tea is also generally composed only of the unopened bud and/or first leaves (Hilal & Engelhardt, 2007). After picking, white tea is dried and retains the white leaf hairs from which it derives its name. Green tea is heat-treated (steaming and/or pan-frying) to inactivate endogenous polyphenol oxidase (PPO), rolled and dried. At the other extreme, during black tea production there is no heat-inactivation of PPO and a “fermentation” or oxidation phase after rolling allows large-scale PPO-catalyzed conversion of simple phenolics to more complex forms and forms the dark coloration. As a result, white, green and black teas differ in their sensorial properties and have markedly different chemical compositions (e.g. Del Rio et al., 2004, Hilal and Engelhardt, 2007, Mizukami et al., 2007, Wang and Ho, 2009).

The major phenolics present in teas are the flavan-3-ols and the flavonols. The flavan-3-ols are characterized by (−)epicatechin and its galloylated derivatives, especially in green tea, whereas black tea has lower amount of these derivatives due to their oxidative conversion into theaflavins and thearubigins (Balentine, 1992, Finger et al., 1992, Del Rio et al., 2004, Mizukami et al., 2007). The flavonols are mainly derivatives of quercetin and kaempferol (Del Rio et al., 2004, Price et al., 1998) but there are smaller amounts of tannins and hydroxycinnamate derivatives. Of course, teas also contain substantial and physiological relevant levels of caffeine and theobromine (e.g. Roberts & Barone, 1983).

Epidemiological studies have suggested correlations of tea intake with favorable outcomes with regard to cardiovascular disease (Grassi et al., 2008), cancer incidence (Yang, Maliakal, & Meng, 2002), inflammation (Gonzalez de Mejia, Vinicio Ramirez-Mares, and Puangpraphant, 2009), obesity (Hsu and Yen, 2007, Wolfram et al., 2006) and type 2 diabetes risk (Venables, Hulston, Cox, and Jeukendrup, 2008). Indeed, a range of mechanisms have been proposed for the beneficial effects of tea and health (e.g. Higdon and Frei, 2003), which largely focus on the polyphenol components, especially the flavan-3-ols.

Considering the epidemic of obesity now forecasted for the Western World (Anon, 2003), the possibility that tea intake could influence obesity through lipid metabolism and digestion is intriguing. Tea, and phenolic components of tea, have been suggested to have anti-obesity and anti-diabetic effects in humans (Kao, Chang, Lee, & Chen, 2006), to reduce adipose mass in rodent models (e.g. Kim et al., 2009) and to influence lipid digestion in vitro (Juhel et al., 2000). In this study we compare examples of black, green and white teas for their ability to inhibit pancreatic lipase in vitro and attempt to identify the active polyphenolic components.

Section snippets

Tea extraction

Black tea (Tetley) and green tea (Clipper, Green China Tea) were purchased at a local supermarket and hand picked, loose leaf white tea was a gift [from Mr. White, Director of Honeybush & Butterbum Ltd, St Peter’s Gate, Charles St, Sunderland SR6 0AN (www.t-please.com)]. The black and green teas were removed from their bags and weighed. An amount of loose white tea (∼2 g) equivalent to the green tea was weighed into flasks. Triplicate tea samples were extracted with 200 ml of boiled water and

Results

The black tea infusions yielded the highest phenol content (217 ± 0.9 mg GAE total) whereas white tea and green tea provided lower amounts (194 ± 1.4 and 176 ± 1.1 mg GAE total, respectively). However, because the infusions were made from the tea bags as supplied, the order was different when expressed as mg/g dry weight with white tea yielding the highest phenol content (97 ± 0.7 mg GAE/g) compared to 89.1 ± 0.5 (green tea) and 67.9 ± 0.3 (black tea). These values are in the same range as previous

Discussion

The main difference between white and green tea was in the amounts of strictinin and digalloyl glucose derivatives. Fractionation on Sephadex LH-20 suggested that the strictinin content was most important for lipase inhibition. The variation in EC50 values noted between lipase batches was caused by variation in protein content which re-emphasizes the difficulty in comparing EC50 between studies or laboratories. The amelioration of inhibition by higher levels of non-enzymatic protein suggests

Acknowledgements

We acknowledge the gift of white tea from Honeybush & Butterbum Ltd, via Dr Ed Okello, University of Newcastle. We also thank the École Nationale Supérieure d’Agronomie et des Industries Alimentaires, Nancy, France for allowing Anais Gondoin to spend her internship training period at SCRI. We also thank the Rural and Environment Research and Analysis Directorate, Scottish Government for support.

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