Shading of Medical Plants Affects the Phytochemical Quality of Herbal Extracts

Abstract

The manipulation of light intensity by shade nets can lead to exchanges in the phytochemical quality and antioxidants ofsome herbs. This study aimed to determine whether shading by pearl nets (50% shade index) could improve the bioactive compounds in several medicinal herbs such as thyme (Thymus vulgaris L.), marjoram (Origanum majorana L.), oregano (Origanum vulgare L.), lemon balm (Melissa officinalis L.), and peppermint (Mentha piperita L.), and their correspondingherbal extracts during a four-week maceration process in ethanol. Oregano and thyme provided the highest yield of total extractive substances (TES) from both shaded and non-shaded plants. Among all studied herbs, the highest level of antioxidants, expressed as total phenolic content (TPC) was found in extracts from shaded plants of lemon balm. Herbal extracts produced from non-shaded thyme and marjoram had higher flavonoid contents compared to herbal extracts from shaded plants. Accumulation of the investigated secondary metabolites depends more on the specificity of a plant species rather than light intensity. This study was an initial step in the production of medicinal plants with an increased quantity of antioxidant and other bioactive compounds during the maceration process in extracts, aimed to be used as natural alcoholic productwith added value.

Keywords

• shading
• mint plants
• maceration
• herbal extracts
• natural antioxidant