Characterisation of bioactive compounds in berry juices by traditional photometric and modern microplate methods

Abstract

Berries and berry production are an important economic factor. Berries contain nutritive components but also pertinent non-nutritive bioactives like phenolic-type phytochemicals. It is well accepted that consumption of bioactives from berries prevent or delay chronic and degenerative diseases. Therefore, a thorough evaluation of bioactive compounds is of utmost interest to assess berry quality. The most accepted photometric methods for the determination of bioactive compounds are presented for conventional cuvette and modern microplate applications. All methods are precisely described and advantages of the microplate methods are discussed. Cuvette and microplate methods show slightly different sensitivity and limits of detection depending on concentrations used for reagents and standard compounds. In general, with microplate methods reagents can be saved up to 12-fold and less time to perform the analyses is needed (up to factor 33). Applicability of all the methods has been shown with selected berry juices. Among all analysed commercial juices, blueberry juice had the highest content of total polyphenols, flavonoids, proanthocyanidins, while the lowest content was observed in pomegranate juice. Blueberry juice had also the highest antioxidant capacity measured by TEAC by ABTS, FRAP and ORAC method when compared to the cranberry, açai, goji and pomegranate juice.

Intra-laboratory validation of microplate methods for total phenolic content and antioxidant activity on polyphenolic extracts, and comparison with conventional spectrophotometric methods

“…In the case of the DPPH microplate method the LOD and LOQ were 12.07 and 36.58 μmol L −1 of Trolox equivalents, respectively. As expected, because of the greater sensitivity of the Horszwald and Andlauer method, 13 the LOQ (0.015 mg L −1 GAE) of their TPC microplate method is lower than the LOQ of this work. On the contrary, the greater sensitivity of DPPH microplate method of this work, resulted in a lower LOD than that obtained by Horszwald and Andlauer, 13 which was 50 μmol L −1 of Trolox.…”

α-Glucosidase inhibitory activities, functional properties, and safety of green tea polysaccharides as a potential source of dietary supplement

“…The content of total phenolics was determined according to the procedure described by Horszwald and Andlauer (2011), using the Folin-Ciocalteu phenol reagent. The content of total phenolics was calculated from a standard curve of gallic acid and expressed as grams of gallic acid equivalents (GAE) per 100 g of sample.…”

Valorisation of theanine from decaffeinated tea dust in bakery functional food

“…Total polyphenolic content (TPC) was determined according to the method of Horszwald & Andlauer () using an Infinite M200 Pro Multimode Microplate reader (Tecan GmbH, Austria) equipped with two‐channel injector system. Briefly, 25 μL aqueous sample extract was placed in microplate's well, and 250 μL Folin‐Ciocalteau's reagent (diluted with water 1:15) was automatically added by the injector.…”