Enhanced Extraction of Phenolic Compounds using Biobased Solvents as Hydrotropes

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The impact of size and shape in the performance of hydrotropes: a case-study of alkanediols

Publication . Abranches, Dinis O.; Soares, Bruna de Paula; Ferreira, Ana M.; Shimizu, Seishi; Pinho, Simão; Coutinho, João A.P.

Inspired by the recently proposed cooperative mechanism of hydrotropy, where water molecules mediate the aggregation of hydrotrope around the solute, this work studies the impact of apolar volume and polar group position on the performance of hydrotropes. To do so, the ability of two different families of alkanediols (1,2-alkanediols and 1,n-alkanediols) to increase the aqueous solubility of syringic acid is initially investigated. Interestingly, it is observed that in the dilute region (low hydrotrope concentration), the relative position of the hydroxyl groups of the alkanediols does not impact their performance. Instead, their ability to increase the solubility of syringic acid correlates remarkably well with the size of their alkyl chains. However, this is not the case for larger hydrotrope concentrations, where 1,2-alkanediols are found to perform, in general, better than 1,n-alkanediols. These seemingly contradictory findings are reconciled using theoretical and experimental techniques, namely the cooperative model of hydrotropy and chemical environment probes (Kamlet–Taft and pyrene polarity scales). It is found that the number of hydrotropes aggregated around a solute molecule does not increase linearly with the apolar volume of the former, reaching a maximum instead. This maximum is discussed in terms of competing solute–hydrotrope and hydrotrope–hydrotrope interactions. The results suggest that hydrotrope self-aggregation is more prevalent in 1,n-alkanediols, which negatively impacts their performance as hydrotropes. The results reported in this work support the cooperative model of hydrotropy and, from an application perspective, show that hydrotropes should be designed taking into consideration not only their apolar volume but also their ability to stabilize their selfaggregation in water, which negatively impacts their performance as solubility enhancers.

2022Journal article

Open access

Juçara fruit (Euterpe Edulis Martius) valorization combining emergent extraction technologies and aqueous solutions of alkanediols

Publication . Soares, Bruna de Paula; Ferreira, Ana M.; Justi, Marina; Rodrigues, Luiz G.G.; Oliveira, José V.; Pinho, Simão; Coutinho, João A.P.

Anthocyanins from juçara fruits were extracted by pressurized liquid extraction (PLE) or ultrasound-assisted extraction (UAE), using aqueous solutions of 1,2-alkanediols and glycerol ethers as biobased solvents. The PLE (100 bar, 13 min, 1 mL/min flow rate) in the optimal extraction conditions originated 23.1 mganthocyanins gdry biomass -1. On the other hand, the UAE was 10 min long, and the optimal conditions using 1,2-propanediol were 42.6 wt%, 160 W, and pH 7.0, leading to 50 mganthocyanins gdry biomass 􀀀1. Extractions at the UAE optimized conditions, with aqueous solutions of five different 1,2-alkanediols and three glycerol ethers were performed, and compared to water and ethanolic extracts. The biobased solvent solutions presented anthocyanin yields up to 33% higher than water, and were shown to be as efficient as ethanol/water, but generated extracts with higher antioxidant capacity. The anthocyanin-rich extract of juçara, obtained with 1,2-propanediol, was used in the production of a natural soap and incorporated into a cream, showing that the addition of the juçara extract resulted in an antioxidant capacity in both products.

2023Journal article

Open access