Effect-Directed Profiling of Powdered Tea Extracts for Catechins, Theaflavins, Flavonols and Caffeine

Abstract

The antioxidative activity of Camelia sinensis tea and especially powdered tea extracts on the market, among others used as added value in functional foods, can considerably vary due to not only natural variance, but also adulteration and falsification. Thus, an effect-directed profiling was developed to prove the functional effects or health-promoting claims. It took 3–12 min per sample, depending on the assay incubation time, for 21 separations in parallel. Used as a fast product quality control, it can detect known and unknown bioactive compounds. Twenty tea extracts and a reference mixture of 11-bioactive compounds were investigated in parallel under the same chromatographic conditions by a newly developed reversed phase high-performance thin-layer chromatographic method. In eight planar on-surface assays, effect-directed tea profiles were revealed. Catechins and theaflavins turned out to be not only highly active, but also multi-potent compounds, able to act in a broad range of metabolic pathways. The flavan-3-ols acted as radical scavengers (DPPH∙ assay), antibacterials against Gram-positive Bacillus subtilis bacteria, and inhibitors of tyrosinase, α-glucosidase, β-glucosidase, and acetylcholinesterase. Further effects against Gram-negative Aliivibrio fischeri bacteria and β-glucuronidase were assigned to other components in the powdered tea extracts. According to their specifications, the activity responses of the powdered tea extracts were higher than in mere leaf extracts of green, white and black tea. The multi-imaging and effect-directed profiling was not only able to identify known functional food ingredients, but also to detect unknown bioactive compounds (including bioactive contaminants, residues or adulterations).

Is Our Natural Food Our Homeostasis? Array of a Thousand Effect-Directed Profiles of 68 Herbs and Spices

“…At an optical density (OD 600 ) between 0.8 and 1.1, the culture was ready to use for EDA. An aliquot of the bacteria suspension (2 ml) was sprayed on the planar chromatogram (red nozzle, level 6) ( Morlock et al, 2021b ). The plate was incubated at 37°C for 2 h. As substrate solution (2 mg/ml), MTT was freshly prepared in phosphate-buffered saline.…”

“…Once the culture showed brilliant blue fluorescence by shaking in the dark, it was ready for use. An aliquot of the bacteria suspension (3 ml) was sprayed on the plate (blue nozzle, level 6) and directly recorded (BioLuminizer 2, CAMAG) ( Morlock et al, 2021a ; Morlock et al, 2021b ). The native bioluminescence (depicted as a greyscale image) was documented in ten images at time intervals of 3 min.…”

“…The initial AChE and BChE inhibition assays ( Marston et al, 2002 ) were modified ( Hage and Morlock, 2017 ; Morlock et al, 2021b ). The plates were pre-wetted with 0.5 ml TRIS-HCl buffer (7.55 mg/ml TRIS, pH 7.8 adjusted with HCl, green nozzle, level 6).…”

“…The tyrosinase inhibitor potential was investigated according to an improved ( Morlock et al, 2021b ) workflow ( Taibon et al, 2015 ). To prepare the substrate solution, 45 mg levodopa, 25 mg CHAPS, and 75 mg PEG 8000 were dissolved in 10 ml of phosphate buffer (1.4 mg/ml K 2 HPO 4 , 1.68 mg/ml Na 2 HPO 4 , pH 6.8) and stored at 4°C until use.…”

High‐performance thin‐layer chromatography based approach for bioassay and ATR–FTIR spectroscopy for the evaluation of antioxidant compounds from Asparagus racemosus Willd. aerial parts

“…HPTLC-EDA-UV/vis is implemented for the screening of the natural product from such complex extracts. The efficient separation and/or isolation of nonvolatile bioactive molecules from plant ingredients is possible with liquid chromatography (Morlock et al, 2021).…”