Acetic acid buffer as extraction medium for free and bound phenolics from dried blackcurrant (Ribes nigrum L.) skins

Abstract

The aim of this study was to investigate the effects of different solvent and extraction temperatures on the free and bound phenolic compounds and antioxidant activity of dried blackcurrant skins (DBS). Apart from acetic acid buffer solution, different solvent systems, including water, methanol, and mixtures of methanol/water, were also employed and the effects of solvent and temperature (30 and 50 °C) on the free and bound forms of anthocyanins, hydroxycinnamic acids, and flavonols yield were assessed. The results showed that among all solvents, acetic acid buffer resulted in the highest free anthocyanin content (1,712.3 ± 56.1 mg/100 g) (P < 0.05) after 2 hr extraction at 50 °C from DBS, while lower amounts of bound anthocyanins and anthocyanidins were detected after acid hydrolysis. Acetic acid buffer extracts exhibited the highest free hydroxycinnamic acid content (268.0 ± 4.5 mg/100 g), total phenolic content (3702.2 ± 259.3 mg GAE/100 g), and DPPH activity (60.7 ± 2.0% of inhibition). However, their free flavonol content was slightly lower (60.2 ± 0.8 mg/100 g) compared to 100% methanol at 30 and 50 °C (71.4 ± 1.5 mg/100 g and 71.5 ± 6.2 mg/100 g, respectively). Two‐way ANOVA indicated interactions between solvent and temperature (P < 0.05), which suggested that the relationship between solvent and phenolic compounds depends on the extraction temperature. Practical Application Overall, acetic acid buffer is more environmental friendly, efficient, and cost effective than other solvents, thus, offering an improved extraction method for phytochemicals as valuable ingredients for nutraceutical applications, from underutilized dried blackcurrant skins (DBS).

Major Phytochemicals: Recent Advances in Health Benefits and Extraction Method

“…It can be used for the extraction of flavonoids, phytosterols, alkaloids, and volatile oils. Cyclohexanes are used for the extraction of fats, waxes, and oils [ 10 , 97 , 98 , 99 ]. The detailed considerations for the suitable solvent for the extraction of phytochemicals have been discussed by Kim and Wijesekra [ 69 ].…”

Stability Enhancement of Anthocyanins from Blackcurrant (Ribes Nigrum L.) Pomace through Intermolecular Copigmentation

“…Determination of the antioxidant activity using the DPPH radical scavenging activity was carried out according to the method of Azman et al [ 29 ] with some modifications. Briefly, 100 μL of the sample was mixed with 2 mL of 0.15 mM DPPH reagent, which was prepared in methanol.…”

“…Annually, more than 300 tonnes of blackcurrant by-products are produced in the UK, containing high amounts of anthocyanins (14–18 mg/g) [ 29 ]. These by-products can be adopted relatively easily by the food industry and have been used as a natural food colorant for many years [ 7 , 30 ].…”

“…These by-products can be adopted relatively easily by the food industry and have been used as a natural food colorant for many years [ 7 , 30 ]. DBP constitutes four types of non-acylated anthocyanins, namely, delphinidin-3- O -rutinoside (D3R), cyanidin-3- O -rutinoside (C3R), delphinidin-3- O -glucoside (D3G) and cyanidin-3- O -glucoside (C3G) [ 29 ] ( Figure 3 ). However, they are less stable than the acylated forms; thus, a reaction such as copigmentation must be carried out in order to increase their stability.…”

Production of innovative antioxidant‐rich and gluten‐free extruded puffed breakfast cereals from purple sweet potato ( Ipomoea batatas L.) and red rice using a mixture design approach

“…The solvent gradient used was: 0-15 min, 15% to 35% B; 15-30 min, 35% to 60% B; 30-40 min, 60% to 80% B; and 40-45 min, 80% to 15% B. The flow rate was 1.0 ml/min, and the injection volume was 20 μL (Azman et al, 2020).…”