Development and Validation of a 96-Well Microplate Assay for the Measurement of Total Phenolic Content in Ginger Extracts

Abstract

A microplate-based assay was developed for the measurement of total phenolic content in polar ginger extracts, using the Folin-Ciocalteu method. The method optimisation process included investigating the effects of wavelength, incubation time and incubation temperature. The method was relatively robust, with most of these parameters having minimal impact on the results obtained. The optimised method could be conducted at room temperature and required only 20 mins of combined incubation time. The repeatability of the microplate reader was 0.57%, with the gallic acid standards curve showing good linearity (R 2 >0.999). The mean intra-and inter-day reproducibility of the entire assay, which included operator error, were 4.4% and 7.8%, respectively. The optimised method was applied to analyse the total phenolic content of 200 ginger extracts in triplicate within approximately 8 hours of labour time, finding a mean total phenolic content of 1713 ± 235 mg GAE 100 g -1 in the dried ginger powder samples. The total phenolic contents of the ginger samples showed a moderate positive correlation (R 2 = 0.46) with the sum of gingerol and 6-shoagol contents, as measured by high-performance liquid chromatography (HPLC). This method could be useful to aid in screening large numbers of samples for total phenolic content in order to identify high-phenolic genotypes, or for use in quality assurance settings.

Phytochemical composition and biological activity of native Australian ginger (Alpinia caerulea)

“…The leaves showed a moderately high TPC and antioxidant capacity, while the rhizome contained a moderate TPC and a correspondingly low total antioxidant capacity. The TPC found in A. caerulea rhizome was somewhat lower than the average TPC previously found in dried ginger (Z. officinale) samples (1713 ± 235 mg GAE/100 g) [50] and A. officinarum rhizome [51]. Anthocyanins were only detected in the fruit capsule and stem samples.…”

Interactions between polyphenols from Theobroma cacao and Lactobacillales to evaluate the potential of a combined strategy for intestinal free-fatty acid removal

“…One gram of lyophilized extract was dissolved in 20 ml of Milli-Q water, autoclaved, and added to the culture media as needed. Total polyphenolic content (TPC) was determined by the Folin-Ciocalteu colorimetric method using gallic acid as standard, as previously described ( Johnson et al, 2021 ). Control and sample absorbances were measured at 750 nm and results were expressed as mg of gallic acid equivalents per gram of sample (mg GAE/g).…”

Evaluation of several macroalgae species on methane emission and antioxidant activity based on in vitro rumen fermentation characteristics

“…The concentration of phenol in the sample was determined according to [23]. To begin, 100 mg of dried seaweed was mixed with methanol and subjected to 30 minutes of ultrasound sonication.…”