Abstract
Thymus herba-barona, Thymus pseudolanuginosus, and Thymus caespititius decoctions were screened for their phenolic constituents, along with their potential antioxidant, anti-inflammatory, and antibacterial activities. The total phenolic compounds in the extracts of the three plants ranged from 236.0 ± 26.6 mgGAE/g (T. caespititus) to 293.0 ± 30.5 mgGAE/g of extract (T. pseudolanuginosus), being particularly rich in caffeic acid derivatives, namely rosmarinic acid and its structural isomers, as well as flavones, such as luteolin-O-glucuronide. The T. pseudolanuginosus extract presented the best DPPH radical scavenging ability (EC50 = 10.9 ± 0.7 µg/mL), a high reducing power (EC50 = 32.2 ± 8.2 µg/mL), and effectively inhibited the oxidation of β-carotene (EC50 = 2.4 ± 0.2 µg/mL). The extracts also showed NO● scavenging activity close to that of ascorbic acid, and thus might be useful as anti-inflammatory agents. In addition, they exhibited antibacterial activity against gram-negative and gram-positive bacteria. Staphylococcus aureus strains were the most sensitive bacteria to thyme extracts, with minimum inhibitory concentration and minimum bactericidal concentration values in the range of 0.6–3.5 mg/mL. Overall, this work is an important contribution for the phytochemical characterization and the potential antioxidant, anti-inflammatory, and antimicrobial activities of these three Thymus species, which have been poorly explored.
Highlights
The Thymus genus encloses about 350 species, which are well adapted to the hot and dry climate of the Mediterranean region and widespread in the arid parts of the Iberian Peninsula [1,2]
The present study aims to contribute to the clarification of phenolic constituents of T. herba-barona, T. pseudolanuginosus, and T. caespititius, as well as to exploit their free radical scavenging, antibacterial, and anti-inflammatory activities
It is important to note that these three aqueous extracts had a considerably higher total phenolic content than those found by other authors in distinct Thymus plants
Summary
The Thymus genus encloses about 350 species, which are well adapted to the hot and dry climate of the Mediterranean region and widespread in the arid parts of the Iberian Peninsula [1,2]. As for the vast majority of Lamiaceae plants, Thymus are recognized as being strongly aromatic and are widely used as spices to enhance sensory attributes such as the taste and aroma of foods [1] These properties highlight the potential application of Thymus plants in the food industry, e.g., in meat, butter, chewing gum, liqueurs, ice cream, and candy production. Besides flavouring, their usage improves the preservation of food, contributing to the prevention of food oxidation and color changes [3,4]. These applications have been mostly associated with essential oils, nowadays, Thymus polar extracts are an attractive target for the screening of health-promoting properties for possible industrial applications in food, cosmetics, or pharmaceutical industries, among others [1,8]
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