Effect of Alginite on Some Antioxidant Indexes in Extracts of Two Variants of Mentha and Their Toxicity

Abstract

The experimental work aimed to determine the effect of different applications of alginite on some antioxidant indexes in the extracts of the Mentha x piperita L. (cultivars Strawberry Mint and Chocolate Mint), and the acute toxicity of water extracts of the studied mint plants to freshwater invertebrates of the genus Daphnia sp. The content of total polyphenols, phenolic acids, and antioxidant activity were determined by spectrophotometric methods. The OECD manual No. 202 was used for the determination of EC₅₀ 48h in the water extracts of both variants of mint. The content of total polyphenols in all groups of the cv. Chocolate Mint ranged from 3.05 to 3.37 mg CAE/100 g DW. On the other hand, the significantly lower (p < 0.001) content of total polyphenols (from 1.01 to 1.38 mg CAE/100 g DW) was found in all groups with the cv. Strawberry Mint. The antioxidant activity determined by the DPPH method was from 115.7 to 119.5 mg TAEC/100 g DW in the cv. Chocolate Mint, but was 2 times lower (from 48.8 to 65.7 mg TAEC/100 g DW) in the cv. Strawberry Mint. The content of phenolic acids in the cv. Chocolate Mint was significantly higher (but only 1.1-fold), than in the cv. Strawberry Mint. The mean acute toxicity after 48 h exposure of the cv. Chocolate Mint to daphnids was nearly 40 times higher than the mean acute toxicity of the cv. Strawberry Mint (EC50 0.25 mg/L vs. EC50 9.62 mg/L, respectively).  We can conclude, that the cv. Chocolate Mint is a more potent source of substances with antioxidant properties, such as polyphenols and phenolic acids, which is reflected in the significantly increased DPPH radical scavenging activity as compared to the cv. Strawberry Mint. We can only speculate that the higher amounts of the aforementioned active substances in the cv. Chocolate Mint were associated with an increased level of acute toxicity to the tested water invertebrates as compared to the cv. Strawberry Mint. The impacts of alginite application on all studied antioxidant indexes as well on the acute toxicity of the extracts of both variants of mint were not confirmed.