Thymus zygis subsp. zygis an Endemic Portuguese Plant: Phytochemical Profiling, Antioxidant, Anti-Proliferative and Anti-Inflammatory Activities.

Amélia M Silva,João A Santos,Mirko Bunzel,Fernando M Nunes,Eliana B Souto,Judith Schäfer,Carlos Martins-Gomes

doi:10.3390/antiox9060482

Abstract

Thymus zygis subsp. zygis is an endemic Portuguese plant belonging to the Thymus zygis species. Although T. zygis is commonly used as a condiment and as a medicinal herb, a detailed description of the polyphenol composition of hydroethanolic (HE) and aqueous decoction (AD) extracts is not available. In this work, we describe for the first time a detailed phenolic composition of Thymus zygis subsp. zygis HE and AD extracts, together with their antioxidant, anti-proliferative and anti-inflammatory activities. Unlike other Thymus species, T. zygis subsp. zygis extracts contain higher amounts of luteolin-(?)-O-hexoside. However, the major phenolic compound is rosmarinic acid, and high amounts of salvianolic acids K and I were also detected. T. zygis subsp. zygis extracts exhibited significant scavenging activity of ABTS+, hydroxyl (•OH), and nitric oxide (NO) radicals. Regarding the anti-proliferative/cytotoxic effect, tested against Caco-2 and HepG2 cells, the AD extract only slightly reduced cell viability at higher concentrations (IC50 > 600 µg/mL, 48 h exposure), denoting very low toxicity, while the HE extract showed a high anti-proliferative effect, especially at 48 h exposure (IC50 of 85.01 ± 15.10 μg/mL and 82.19 ± 2.46 μg/mL, for Caco-2 and HepG2, respectively). At non-cytotoxic concentrations, both extracts reduced the nitric oxide (NO) release by lipopolysaccharide (LPS)-stimulated RAW 264.7 cells (at 50 μg/mL, HE and AD extracts inhibited NO release in ~89% and 48%, respectively). In conclusion, the results highlight the non-toxic effect of aqueous extracts, both resembling the consumption of antioxidants in foodstuff or in functional food. Furthermore, the HE extract of T. zygis subsp. zygis is a source of promising molecules with antioxidant, anti-inflammatory and anticancer activities, highlighting its potential as a source of bioactive ingredients for nutraceutical and pharmaceutical industries.

Highlights

The genus Thymus, belonging to the Lamiaceae family, includes ca. 350 species of perennial, subshrubs, and aromatic herbs native to Europe and North Africa, with many of them being endemic to the Mediterranean region [1,2,3]
The HE was previously shown to extract 99% of the total extractable compounds [27], it was chosen as the method to obtain the full “free” phenolic composition of T. zygis subsp. zygis
It allows to analyze the phenolic compounds that are available with a common preparation for human consumption, as these plants are used as herbal teas, seasoning, and condiments

Summary

Introduction

The genus Thymus, belonging to the Lamiaceae family, includes ca. 350 species of perennial, subshrubs, and aromatic herbs native to Europe and North Africa, with many of them being endemic to the Mediterranean region [1,2,3]. They grow well in a climate with moderate to warm temperatures, in well-drained to dry soils (usually they grow on rocks, stones, or sand), and in sunny places [4] Besides these ecological preferences, some Thymus species are cultivated, especially in calcareous light, dry, stony soils and heavy wet soils, but lose some aromatic properties [4]. Thymus zygis is commonly named “erva-de-Santa-Maria”; “sal-da-terra”, “serpão-do-monte” (Portuguese), white-thyme, and others [7,8]. For this species, three subspecies are described, namely Thymus zygis subsp.

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