Seasonal Variation of Antioxidant Capacity, Phenols, Minerals and Essential Oil Components of Sage, Spearmint and Sideritis Plants Grown at Different Altitudes

Antonios Chrysargyris,Nikolaos Tzortzakis,Efstathios Evangelides

doi:10.3390/agronomy11091766

Abstract

Medicinal and aromatic plants are well appreciated for their antioxidant and biocidal activities, while great variation on these activities can be related to the species, environmental conditions and harvesting period. In the present study, the seasonal variation of the antioxidant activity, mineral content, yield and chemical composition of the essential oils (EOs) of sage (Salvia officinalis L.), sideritis (Sideritis perfoliata L. subsp. perfoliata) and spearmint (Mentha spicata L.) were tested under two different environmental conditions, each with a different altitude (namely mountainous and plain). Season affected total phenolic content and antioxidant capacity with increased values during winter and lower values during summer period. In summer, plants accumulated more Fe and had higher EO yield, while P and Na were accumulated more in winter. Altitude had a lesser effect on antioxidant capacity of the plants; however, increased minerals (N, K, Na and Ca) accumulation was found in plain areas. Sage plants had the highest antioxidant capacity, Zn content and EO yield. Sideritis had increased Fe content and spearmint plants revealed high N, Na and Mg levels. Furthermore, altitude and season had an impact on the content of main EOs components in all species. FRAP and ABTS were variably correlated with total phenols and minerals, depending on the species, season and altitude. In few cases, antioxidant activity was found to be inversely linked to some EO components (e.g., α-thujone in sage). Finally, the antioxidant content, minerals and EO yield and composition of the examined MAPs were all altered by season and altitude. These findings can be utilized to implement sage, sideritis and spearmint farming in specific ecosystems, determining the season and areas for harvesting the plants, in order to produce high-value products.

Highlights

Medicinal and aromatic plants (MAPs), commonly known as herbs or spices, and their related plant extracts and essential oils (EOs) have been highly valued and widely used for centuries, of regardless the lack of scientific proof for their actual bioactive mechanisms and functions, which are still under research [1,2]
We determined whether the content of total phenols and the antioxidant activity of three MAP species were affected by the season [46] and by the altitude, as it has been previously reported [32,34]
The levels of total phenols, antioxidant activity and mineral content of sage, sideritis and spearmint were investigated in terms of the impact of environmental condition-altitude and season as well as their correlation to the EO yield and composition

Summary

Introduction

Medicinal and aromatic plants (MAPs), commonly known as herbs or spices, and their related plant extracts and essential oils (EOs) have been highly valued and widely used for centuries, of regardless the lack of scientific proof for their actual bioactive mechanisms and functions, which are still under research [1,2]. Antioxidant-rich foods are popular because they can assist in reducing the burden of age-related chronic diseases by scavenging reactive oxygen species (ROS) [5]. Plants produce a wide range of secondary metabolites, such as phenolic compounds, as part of their defense mechanism against oxidative damage caused by ROS and other abiotic and biotic stressors [2]. These compounds may protect human health when MAPs and/or their components are consumed through diet [6]. Hydrogen atom donation, single oxygen quenching, metal ion chelation and activities as an oxidation substrate are all mechanisms involved in phenolic compounds’ antioxidant activity [6]

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