2.1. Plant Material and Chemicals

All samples of Rhododendron adamsii (215 samples totally) were collected in the tundra habitat in Republic Sakha Yakutia, Lena River delta, Kubalakh-Aryta Island, Orto-Khaya Mountain (72°26′22.0″ N, 126°18′09.0″ E, 280 m a.s.l.) in January (15.I.2019–17.I.2019; 15 samples), March (12.III.2019–15.III.2019; 19 samples), May (16.V.2019–20.V.2019; 26 samples), June (12.VI.2019–16.VI.2019; 31 samples), July (15.VII.2019–17.VII.2019; 42 samples), August (17.VIII.2019–22.VIII.2019; 36 samples), October (12.X.2019–15.X.2019; 27 samples), and December (19.XII.2019–23.XII.2019; 19 samples). One sample consisted of 10–20 leaves (average length 2 cm, height 1 cm) collected from one bush. The species was authenticated by Dr. N.I. Kashchenko (IGEB SB RAS, Ulan-Ude, Russia). The plant material was dried in the ventilated heat oven at 40 °C within 7–10 days and stored at 3–4 °C before analysis. The reference compounds were purchased from Cayman Chemicals (Ann Arbor, MI, USA), ChemFaces (Wuhan, Hubei, China), Extrasynthese (Lyon, France), MCE Med Chem Express (Monmouth, NJ, USA), Sigma-Aldrich (St. Louis, MO, USA), and Wuhan Chem Norm Biotech Co., Ltd. (Wuhan, China) (Table S1).