Four New Iridoid Glucosides from Ajuga reptans

Abstract

NoteAjuga reptans L. (Labiatae) is native to Europe, and has been used as a traditional vulnerary.1) This plant has been reported to contain iridoids, 1,2) diterpenoids, [3][4][5][6][7] ecdysteroids, [8][9][10] and anthocyanins.11) The present paper describes the isolation and structural elucidation of four new iridoid glucosides (1-4) along with four known iridoid glucosides (5-8), one known diterpenoid glycoside (9), one known aliphatic alcohol glycoside (10), and three known ecdysteroids (11-13), as well as the antioxidative activities of 9.Dried whole plants of A. reptans were extracted with methanol (MeOH). This extract was successively subjected to Diaion HP20, silica gel, and Chromatorex octadecyl silica (ODS) column chromatography as well as HPLC using ODS to yield 13 compounds (1-13).Compounds 5-13 were identified as reptoside (5), 12) harpagide (6), 12) 6-epi-acetyl harpagide (7), 13) acetyl harpagide (8), 12) ajugaside A (9), 15) ajugalactone (11), 9) 20-hydroxyecdysone (12), 16) and 20-hydroxyecdysone 3-acetate (13), 16) respectively, based on their physical and spectral data ( Fig. 1).Compound 1, tentatively named ajureptaside A, was obtained as a syrup, and exhibited an [MϩNa] ϩ ion peak at m/z 477 in the positive-ion FAB-MS. (d 99.9, 74.6, 78.0, 71.8, 77.8, 63.0). These 1 H-and 13 C-NMR signals (Tables 1 and 2, respectively) were assigned with the aid of 1 H-1 H correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple bond correlation (HMBC) spectra. The planar structure of 1, which was an iridoid glucopyranoside whose aglycone moiety (Agl) possessed three hydroxyl groups at C-4, C-5, and C-6, one methoxy group at C-3, and one acetoxy group at C-8, could be determined as illustrated in Fig. 2. The relative configurations at C-1, C-3, C-4, C-5, C-6, C-8, and C-9 of Agl were concluded to be S*, R*, R*, S*, R*, S*, and S*, respectively, on the basis of the nuclear Overhauser and exchange spectroscopy (NOESY) spectrum, in which key correlations were observed between H-1 of Agl and H 3 -10 of Agl; H-4 of Agl and H-6 of Agl; and H-4 of Agl and H 3 -10 of Agl, as shown in Fig. 3, and by analysis of the coupling constants (J H-1-H-9 0 Hz; J H-3-H-4 8.0 Hz) between H-1 and H-9; and H-3 and H-4 in the 1 H-NMR spectrum. Acidic hydrolysis of 1 gave D-glucose, which was confirmed by optical rotation using chiral detection in HPLC analysis, and the coupling constant of the signal due to the anomeric proton [d 4.73 (d, Jϭ8.0 Hz)] indicated the mode of glycosidic linkage of the glucopyranosyl group to be b. Consequently, the structure of 1 was concluded to be 8-Oacetyl-4b-hydroxy-3a-methoxy-dihydroharpagide. Four new iridoid glucosides were isolated from the whole plant of Ajuga reptans L. (Labiatae) along with four known iridoid glucosides, one known diterpenoid glycoside, one known aliphatic alcohol glycoside, and three known ecdysteroids. Their chemical structures were determined on the basis of spectroscopic data and chemical evidence. The diterpenoid gl...

Phytochemical Composition, Antioxidant, Antimicrobial and in Vivo Anti-inflammatory Activity of Traditionally Used Romanian Ajuga laxmannii (Murray) Benth. (“Nobleman’s Beard” – Barba Împăratului)

“…In comparison with other research, A. laxmannii showed a higher antiradical capacity. For example, a study concerning antioxidant capacity of A. turkestanica reported a value of 57.84 ± 4.19 μg/mL ( Mamadalieva et al, 2013 ), whereas a similar study concerning A. reptans reported a slightly higher value (65.7 ± 3.82 μg/mL) ( Ono et al, 2011 ). A similar antiradical activity was reported by Movahhedin et al (2016) for A. chamaecistus subsp.…”

“…Additionally, several phytochemical studies on Ajuga species have shown the presence of iridoids, diterpenes, phytoecdy steroids, flavonoids, sterol glycosides and phenylethanoid glycosides as the main secondary metabolites of the genus ( Manguro et al, 2006 , 2011 ; Ono et al, 2011 ; Atay et al, 2016 ).…”

Study on Ajuga reptans Extract: A Natural Antioxidant in Microencapsulated Powder Form as an Active Ingredient for Nutraceutical or Pharmaceutical Purposes

“…Monoterpenoids ( 1 – 3 ) and polyphenols ( 4 – 7 ) are characteristic secondary metabolites of the Ajuga genus [ 11 , 12 ], exerting many health properties, having antioxidant, anti-inflammatory, and antibacterial effects [ 7 , 13 ].…”

“…The folk medicine attributes to A. reptans L. anti-diabetic, anti-hypertensive [ 9 ], diuretic [ 10 ], and hepatoprotective properties [ 11 ]. Ecdysteroids, triterpenes, sterols, diterpenes, iridoids, and flavonoids have been identified as bioactive compounds providing antioxidant power, antimicrobial, and anti-inflammatory activity [ 6 , 11 , 12 , 13 ]. Moreover, Ajuga extracts and the major phenylpropanoids were demonstrated as both antioxidant and UV protector agents in cosmetic formulations to counteract premature cell ageing [ 14 ].…”

Dualistic Properties of Cosmetic Formulations Based on Phenylpropanoids from <i>Ajuga reptans</i>

“…Ajuga reptans L. is frequently used in the traditional medicine of many countries especially, the eastern part of Europe, for its skin healing properties. The extracts obtained from "bugle" (Ajuga reptans L.) most likely own their activity to the content of polyphenols of the flavonoid and polyphenol-carboxylic acids type (antioxidant, vascular and antimicrobial properties), as well as of iridoids (anti-inflammatory and wound healing) [1]. Moreover, the research on cosmetic product for sun protection is evolving towards the development of natural products.…”