Antiradical activity and bioactive substances of Eleutherococcus senticosus (Rupr. and Maxim) grown under hydroponic and soil conditions in Ararat Valley and Dilijan Forest zone

Abstract

Background: Eleutherococcus (E.) senticosus (Rupr. and Maxim) is a rare and valuable adaptogenic medicinal plant of the Araliaceae family, native to northeast Asia, introduced into Armenia. It is widely used in Oriental medicine for its pharmaceutical and medicinal properties. Due to the rich composition of bioactive substances (BAS) (phenylpropanoids, eleutherosides, phenols, vitamins, etc.), all organs of E. senticosus - roots, leaves, fruits, and stems - are used in medicine to treat cardiovascular diseases, cerebral ischemia, depression, diabetes, Alzheimer's and Parkinson's diseases, etc. E. senticosus, like Panax ginseng, is a natural immunomodulator and adaptogen in health and functional nutrition. Recently, the use of this valuable plant in foods (tea, wine, etc.), medicines, dietary supplements and cosmetics has become popular in the West. Thus, in the stressful times of the 21st century, studying and including such adaptogenic medicinal plants in diet and herbal medicine is essential and relevant.

Objective: To study the BAS, antiradical activity, and gross β-radioactivity in the medicinal raw material (leaf, stem, fruit, and root) of E. senticosus grown in soilless (hydroponics- EBB and FLOW) and soil conditions of the experimental field of the Institute of Hydroponics Problems (IHP) in Ararat Valley and Dilijan Forest Experimental Station (DFES). 

Methods: Total flavonoids, total eleutherosides, and phenolic acids were determined in ethanol extracts obtained from medicinal raw materials using the spectrophotometric method. The antiradical activity of ethanolic extracts of leaves was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) reduction reaction. The spectra were measured using an Agilent Cary 60 UV-Vis spectrophotometer. A radiochemical method was used to determine the gross β-radioactivity of the samples. 

Results: It has been found that the content of BAS in the leaves, stems, fruits, and roots of E. senticosus varies depending on the growing conditions. The total flavonoid content of leaf, stem, root and fruit extracts of E. senticosus grown in soil conditions was 1.5, 2.0, 1.2, and 2.3 times lower, than those of hydroponically grown plants. It was revealed that all the studied parts of hydroponic plants of E. senticosus exceeded those of soil plants (IHP and DFES) in eleutheroside content: leaves - by 1.5 and 1.3 times, fruits - by 1.2 times, stems - by 1.2, roots - by 1.2 and 1.1 times, respectively. Comparative characteristics of the contents of the studied phenolic acids in various parts (leaf, stem, fruit, root) of E. senticosus are the same: chlorogenic acid > rosmarinic acid > gallic acid > caffeic acid. Leaf extracts of E. senticosus grown under hydroponic and soils (IHP and DFES) conditions revealed the highest antioxidant activity at their active density of 500 μg/mL, neutralizing 87.2 - 90.9 % of the free radicals in solution. Radiochemical analyses showed that the gross β-radioactivity of leaves, stems, fruits and roots of E. senticosus in hydroponics exceeded that of similar parts of plants grown in soils (IHP Ararat Valley and DFES) by 1.3 and 1.9 times, 2.2 and 2.4 times, 1.5 and 2.0 times, 2.6 and 3.6 times, respectively. Furthermore, in hydroponics and soil, various parts of E. senticosus form the following decreasing range of gross β-radioactivity: fruit > leaf > stem > root. Therefore, the plant raw material of E. senticosus can be considered radio-ecologically safe, as its gross β-radioactivity did not exceed 1.0 Bq/g according to the World Health Organization (WHO) standards.

Conclusion: According to the results of the study, various parts of E. senticosus (leaf, stem, root, fruit) grown in outdoor hydroponics and in the soils of Ararat Valley and DFES are rich sources of bioactive substances for pharmaceuticals, functional foods, and skin care. All studied variants of E. senticosus leaf extracts showed high antioxidant activity, possibly due to the high content of phenolic compounds. Regardless of the growing method (hydroponics and soil) and the different radio-tension zones, the medicinal raw material of E. senticosus can be considered radio-ecologically safe.

Keywords: medicinal raw material, eleutherosides, flavonoids, phenolic acids, gross β-radioactivity