Abstract
The effects of solvent and time of extraction on the antioxidant properties and phenolic profiles of 13 herbs and spices used for food seasoning and preservation were investigated. The profiles of phenolics in plant material were analysed by UPLC, and the chemometric approach was used for the deeper evaluation of relationships between phenolic compounds and the antioxidant properties of the samples. The best extraction conditions enabling to obtain the highest total phenolics and the antioxidant activity were: long time extraction (24 h) with 50% aqueous ethanol. The most potent antioxidant was clove with the ABTS—2495.85 µmol/g, DPPH—1443.35 µmol/g and FRAP—1310.91 µmol/g, which resulted from the high total phenolic content (TPC—167.22 mg GAE/g) and total flavonoid content (TFC—26.22 mg QE/g). Wide variations in the antioxidant activity (ABTS: 7.31—2495.85 µmol/g) and TPC (0.87–167.22 mg GAE/g) were observed with black seed extract showing one of the lowest values of the parameters studied. High linear correlation (above 0.95) calculated for the parameters showed significant contribution of phenolics to the antioxidant activity of spices. UPLC analysis together with PCA (principal component analysis) confirmed this relation and ABTS, FRAP, DPPH, TFC, TPC, total phenolic acids, protocatechuic acid, t-cinnamic acid, p-hydroxybenzoic acid determined sample distribution along PC1 (principal component 1), whereas total flavonoids determined by UPLC, kaempferol, catechin and luteolin along PC2. All samples were discriminated with 100% classification’s propriety according to GDA (general discrimination analysis) which proved huge diversity among phenolic profiles and the antioxidant properties of tested samples.
Highlights
Herbs and spices have been used for ages to improve flavour of food and to preserve food from spoilage during storage, to cure or reduce the risk of human diseases
A wide range of Total polyphenol content (TPC) and Total flavonoid content (TFC) values for the spices and herbs tested in this study indicated the huge diversity of the phenolic compounds which could react with the FCR and aluminum chloride, respectively
The third discriminant function (Root 3) was contributed by the PC7 related to Syringic acid (SyA) and PC8 related to caffeic acid (CA)
Summary
Herbs and spices have been used for ages to improve flavour of food and to preserve food from spoilage during storage, to cure or reduce the risk of human diseases. Stuper‐Szablewska investigated such as: microwave-assisted extraction, ultrasound-assisted extraction, enzymatic-assisted extraction, pulsed electric field extraction, supercritical fluid extraction, natural deep eutectic solvent extraction, accelerated solvent extraction [2], the solvent extraction is still the most frequently used procedure to obtain extracts from plant materials The pros of this process are as follows: ease of use, wide applicability and no need of usage the advanced equipment. From the environmental point of view the solvent extraction does not belong to the green chemistry methods since a great number of waste are produced with potentially dangerous residues depending on type of solvent used. The high diversity of phenolics is the straight effect of the multiple functional groups varying in type, number and position in the compound structure [3]. From the safety point of view ethanol and ethanol–water solvents could be introduced into food without the risk of product contamination with toxic solvent residues
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