Health-Promoting Effects of Thymus Phenolic-Rich Extracts: Antioxidant, Anti-Inflammatory and Antitumoral Properties

Thymus genus comprises numerous species that are particularly abundant in the West Mediterranean region. A growing body of evidence suggests that many of these species are a rich source of bioactive compounds, including phenolic compounds such as rosmarinic acid, salvianolic acids and luteolin glycosides, able to render them potential applications in a range of industrial fields. This review collects the most relevant studies focused on the antioxidant, anti-inflammatory and anti-cancer of phenolic-rich extracts from Thymus plants, highlighting correlations made by the authors with respect to the main phenolic players in such activities.

Phytochemical Composition and Bioactive Effects of Salvia africana, Salvia officinalis 'Icterina' and Salvia mexicana Aqueous Extracts

In the present study, aqueous extracts of Salvia africana, Salvia officinalis 'Icterina' and Savia mexicana origin were screened for their phenolic composition and for antibacterial, antioxidant, anti-inflammatory and cytotoxic properties. The three aqueous extracts contained distinct phenolic compounds, with S. africana presenting the highest total levels (231.6 ± 7.5 μg/mg). Rosmarinic acid was the dominant phenolic compound in all extracts, yet that of S. africana origin was characterized by the present of yunnaneic acid isomers, which overall accounted for about 40% of total phenolics. In turn, S. officinalis 'Icterina' extract presented glycosidic forms of apigenin, luteolin and scuttelarein, and the one obtained from S. mexicana contained several simple caffeic acid derivatives. S. africana aqueous extract exhibited high antioxidant potential in four methods, namely the DPPH• (2,2-diphenyl-1-picrylhydrazyl) scavenging ability, iron-reducing power, inhibition of β-carotene bleaching and of thiobarbituric acid reactive substances (TBARS), for which EC50 values were equal or only 1.3-3.1 higher than those of the standard compounds. Moreover, this extract was able to lower the levels of nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages (EC50 = 47.8 ± 2.1 μg/mL). In addition, the three sage aqueous extracts showed promising cytotoxic effect towards hepatocellular HepG2, cervical HeLa, and breast carcinoma cells MCF-7. Overall this study highlights the potential of three little-exploited Salvia species, with commercial value for applications in food or pharmaceutical industries.

The Health-Benefits and Phytochemical Profile of Salvia apiana and Salvia farinacea var. Victoria Blue Decoctions

Salvia apiana and Salvia farinacea var. Victoria Blue decoctions were screened for diverse bioactivities, including the ability to counteract oxidative and inflammatory events, as well as to act as cytotoxic and antimicrobial agents. Both extracts showed good activities and that of S. apiana origin was particularly effective regarding the ability to prevent lipid peroxidation and to prevent nitric oxide (NO●) production in lipopolysaccharide (LPS)-activated murine macrophage RAW 264.7 cell line (EC₅₀ = 50 μg/mL). Moreover, it displayed high cytotoxic capacity against hepatocellular carcinoma HepG2, cervical carcinoma HeLa, and breast carcinoma cells MCF-7, but comparatively low effects in porcine liver primary cells, which highlights its selectivity (GI₅₀ = 41–60 μg/mL vs. 362 μg/mL, respectively). Further, it exhibited inhibitory and lethal potential against a panel of Gram-positive and Gram-negative bacteria. It is possible that the bioactive properties of the two Salvia extracts are associated to their phenolic components and, in the particular case of S. apiana, to its richness in phenolic terpenes, namely in rosmanol, hydroxycarnosic acid and a derivative of sageone, which were found in the extract.

Salvia elegans, Salvia greggii and Salvia officinalis Decoctions: Antioxidant Activities and Inhibition of Carbohydrate and Lipid Metabolic Enzymes

Salvia elegans Vahl., Salvia greggii A. Gray, and Salvia officinalis L. decoctions were investigated for their health-benefit properties, in particular with respect to antioxidant activity and inhibitory ability towards key enzymes with impact in diabetes and obesity (α-glucosidase, α-amylase and pancreatic lipase). Additionally, the phenolic profiles of the three decoctions were determined and correlated with the beneficial properties. The S. elegans decoction was the most promising in regard to the antioxidant effects, namely in the scavenging capacity of the free radicals DPPH•, NO• and O₂•⁻, and the ability to reduce Fe3+, as well as the most effective inhibitor of α-glucosidase (EC50 = 36.0 ± 2.7 μg/mL vs. EC50 = 345.3 ± 6.4 μg/mL and 71.2 ± 5.0 μg/mL for S. greggii and S. officinalis, respectively). This superior activity of the S. elegans decoction over those of S. greggii and S. officinalis was, overall, highly correlated with its richness in caffeic acid and derivatives. In turn, the S. officinalis decoction exhibited good inhibitory capacity against xanthine oxidase activity, a fact that could be associated with its high content of flavones, in particular the glycosidic forms of apigenin, scutellarein and luteolin.

Metabolites and Biological Activities of Thymus zygis, Thymus pulegioides, and Thymus fragrantissimus Grown under Organic Cultivation

Thymus plants are marketed for diverse usages because of their pleasant odor, as well as high nutritional value and wealth of health-promoting phytochemicals. In this study, Thymuszygis, Thymuspulegioides, and Thymusfragrantissimus grown under organic cultivation regime were characterized regarding nutrients and phenolic compounds. In addition, the antioxidant and antibacterial properties of these species were screened. The plants were particularly notable for their high K/Na ratio, polyunsaturated fatty acids content and low omega-6/omega-3 fatty acids ratios, which are valuable features of a healthy diet. Caffeic acid and/or its derivatives, mainly rosmarinic acid and caffeoyl rosmarinic acid, represented the majority of the phenolic constituents of these plants, although they were less representative in T. pulegioides, which in turn was the richest in flavones. The latter species also exhibited the highest antioxidant capacity (DPPH● EC50 of 9.50 ± 1.98 μg/mL and reducing power EC50 of 30.73 ± 1.48 μg/mL), while T. zygis was the most active towards Gram-positive and Gram-negative bacteria. Overall, the results suggest that the three thyme plants grown in organic farming are endowed with valuable metabolites that give them high commercial value for applications in different industries.