Sagan Dalya Tea, a New "Old" Probable Adaptogenic Drug: Metabolic Characterization and Bioactivity Potentials of Rhododendron adamsii Leaves

Abstract

Adams' rhododendron (Rhododendron adamsii Rehder) or Sagan Dalya tea is a famous Siberian evergreen medical plant of the Ericaceae family used in traditional medicines of Buryats, Yakuts, and Mongols as a tonic, stimulant, and adaptogenic drug. The high popularity of R. adamsii coupled with poor scientific knowledge prompted the addressing of gaps related to metabolic and biomedical data of Sagan Dalya tea. The application of solid-phase extraction and liquid chromatography-mass spectrometric techniques for the metabolomic study of R. adamsii leaf extracts resulted in the identification of more than 170 compounds, including carbohydrates, organic acids, simple phenol glycosides, triterpene glycosides, flavonoids, prenylated phenols, benzoic acid derivatives, hydroxycinnamates, dihydrochalcones, catechins, and procyanidins, most of which were identified for the first time in the plant. Extended surveys of the seasonal content of all detected compounds prove that specific metabolite variations reflect the bioactivity of R. adamsii extracts. Regarding in vitro methods, the expressed antioxidant potential of R. adamsii extracts was investigated via radical-scavenging, nitric oxide scavenging, and ferrous (II) ion chelating assays. The animal-based swimming to exhaustion test demonstrates the stimulating influence of R. adamsii extract on physical performance and endurance, concluding that the drug could act as an adaptogen. Thus, Sagan Dalya tea (R. adamsii) has confirmed its "old" application as a tonic remedy and requires further precise study as a novel adaptogenic plant.

Keywords: Rhododendron adamsii; Sagan Dalya; adaptogen; antioxidant activity; liquid chromatography-mass spectrometry; seasonal variation; swimming to exhaustion test.

Figure 1

Rhododendron adamsii Rehder (Sagan Dalya) in its natural habitat (Republic Sakha Yakutia, Lena River delta, Kubalakh-Aryta Island, Orto-Khaya Mountain, tundra).

Figure 2

The effect of R. adamsii leaf extracts (solvent: 0–100% methanol) and R. rosea extract (50 mg/kg) on swimming time of mice in swimming to exhaustion test on day 1 (empty bars) and day 10 (shaded bars). *—p < 0.05 vs. control group, day 1; **—p < 0.05 vs. control group, day 10.

Figure 3

Correlation graph between radical scavenging ability of Rhododendron adamsii extracts against 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH; independent variable x in regression equation) and swimming time of mice in swimming to exhaustion test on day 10 (dependent variable y in regression equation). r—correlation coefficient.

Figure 4

High-Performance Liquid Chromatography with Electrospray Ionization Triple Quadrupole Mass Spectrometric Detection (HPLC-ESI-tQ-MS) chromatogram (Total Ion Chromatogram (TIC) mode, negative ionization) of solid-phase extraction (SPE) eluates of R. adamsii leaves (July sample) extract: H₂O eluate (SPE-1; a), MeOH eluate (SPE-2; b), NH₃-MeOH eluate (SPE-3; c), DMSO eluate (SPE-4; d). Compounds are numbered as listed in Table 2. Internal standards used: 20-hydroxyecdysone (IS-I), apigenin-7-O-glucoside (IS-II), apigenin-7-O-glucuronide (IS-III), epigallocatechin O-gallate (IS-IV).

Figure 4

High-Performance Liquid Chromatography with Electrospray Ionization Triple Quadrupole Mass Spectrometric Detection (HPLC-ESI-tQ-MS) chromatogram (Total Ion Chromatogram (TIC) mode, negative ionization) of solid-phase extraction (SPE) eluates of R. adamsii leaves (July sample) extract: H₂O eluate (SPE-1; a), MeOH eluate (SPE-2; b), NH₃-MeOH eluate (SPE-3; c), DMSO eluate (SPE-4; d). Compounds are numbered as listed in Table 2. Internal standards used: 20-hydroxyecdysone (IS-I), apigenin-7-O-glucoside (IS-II), apigenin-7-O-glucuronide (IS-III), epigallocatechin O-gallate (IS-IV).

Figure 5

Structures of known compounds found in R. adamsii. Abbreviation used: Arap—arabinopyranose; Caff—Caffeoyl; Gall—Galloyl; Galp—Galactopyranose; Glcp—Glucopyranose; GlcAp—Glucuronopyranose; Rhap—Rhamnopyranose.

Figure 6

Mass spectra (A,B); negative ionization), UV patterns (C) of cannabigerorcinic acid (CGA) and cannabigerorcinic acid methyl ester (CGA-Me), and fragmentation way of CGA-Me (D).

Figure 7

Mass spectra (A,B); negative ionization), UV patterns (C) of grifolic acid (GRA) and hydroxy-grifolic acid (HGRA), and fragmentation way of GRA (D).

Figure 8

Mass spectra (A,B); negative ionization), UV patterns (C) of daurichromenic acid (DCA) and hydroxy-daurichromenic acid (HDCA), and fragmentation way of DCA (D).

Figure 9

Principal component analysis (PCA) for the content of 171 compounds in 215 samples of R. adamsii leaves collected during various months of the year.

Figure 10

HPLC-UV chromatograms of R. adamsii leave total extract (July sample) before (black) and after preincubation (red) with DPPH^• radicals solution. The excess of DPPH^• radicals signed as DPPH. The basic peaks are numbered as described in Table 3.

Figure 11

Effects of four different R. adamsii leaf extracts (January, May, July, and October samples) and R. rosea extract (50 mg/kg) on swimming time of mice in a two-step swimming to exhaustion test. * —p < 0.05 vs. saline group.