Effect of salicylic acid on phenolic compounds, antioxidant and antihyperglycemic activity of Lamiaceae plants grown in a temperate climate

Abstract

Background: The Lamiaceae family, one of the most important herbaceous and shrub plant families, includes a wide variety of plants with biological and medicinal uses. This study aimed to conduct a comparative analysis of phenolic compounds content and biological activity of extracts from eight species of Lamiaceae plants, cultivated in a temperate climate, and to study the effect of the foliar salicylic acid application on these parameters. Methods: Lamiaceae plants (Lavandula angustifolia, Salvia officinalis, Hyssopus officinalis, Agastache foeniculum, Thymus serpyllum, Mentha × piperita, Origanum vulgare, Monarda didyma) cultivated on field experimental sites. Plants were sprayed with salicylic acid at a concentration of 1 mM. The untreated with salicylic acid plants were used as control. Results: The highest contents of hydroxycinnamic acids and flavonoids in control plants were observed in the Agastache foeniculum (6.4 ± 0.6 mg g-1 and 6.5 ± 0.4 mg g-1 respectively). The highest content of phenolic compounds was found in Monarda didyma (13.8 ± 0.7 mg g-1). Among the control plants, Agastache foeniculum, Hyssopus officinalis, and Mentha × piperita were characterized by the highest antioxidant activity. All the studied extracts had the ability to inhibit α-amylase and α-glucosidase. Significant positive correlations were revealed between the antioxidant activity and the contents of hydroxycinnamic acids, total phenolic compounds, and flavonoids. A high degree of correlation was found between the α-amylase inhibitory activity and the content of hydroxycinnamic acids (r = 0.72, p ≤ 0.05), as well as between the α-glucosidase inhibitory activity and the content of flavonoids (r = 0.83, p ≤ 0.05) and hydroxycinnamic acids (r = 0.81, p ≤ 0.05). The foliar treatment with salicylic acid led to an increase in the contents of hydroxycinnamic acids (in 6 species), flavonoids (in 2 species), total phenolic compounds (in 7 species), antioxidant activity (in 5 species), as well as in α-amylase (in 4 species) and α-glucosidase (in 5 species) inhibitory activity compared to the control plants. Lavandula angustifolia was the most susceptible to foliar treatment with salicylic acid. In this plant species, a significant increase in all studied biochemical parameters was noted. Conclusions: The results obtained on the stimulating effects of salicylic acid can be used to increase the nutritional and pharmacological value of plants of the Lamiaceae family cultivated in temperate climates.

Keywords

• biostimulants
• hormone
• rosmarinic acid
• amylase
• glucosidase
• diabet