Flavonoids from Artemisia santolinifolia

Abstract

Artemisia santolinifolia Turcz. ex Besser is a perennial plant indigenous to Central Asia, southern Siberia, Mongolia, and Yakutia [1, 2]. The flavonoids quercetin, luteolin, rutin, and kaempferol and its glycoside [3] and coumarins scopoletin and umbelliferone [4] were isolated previously from A. santolinifolia. The roots yielded a phenolic natural compound [5]. We studied the aerial part of A. santolinifolia collected in 2008 in the vicinity of Bayanaul, Pavlodar Oblast, Republic of Kazakhstan. The aerial part was extracted with MeOH. The extract was evaporated in a rotary evaporator. The resulting condensed extract was worked up with aqueous alcohol. The filtrate was extracted with CHCl3. Then, the obtained total compounds (74 g) were separated over a column of silica gel (compound–sorbent ratio 1:1.5). Elution by hexane–EtOAc (3.5:6.5) afforded yellow crystalline 1 and 2. Comparison of physicochemical constants and spectral data (PMR and 13C NMR) with the literature identified 1 as the flavonoid 5,4 -dihydroxy-7-methoxyflavone (genkwanin) [6]. 5,4 -Dihydroxy-7-methoxyflavone (genkwanin) (1). 1H NMR spectrum (300 MHz, DMSO-d6, , ppm, J/Hz): 6.78 (1H, s, H-3), 6.32 (1H, d, J = 2, H-6), 6.7 (1H, d, J = 2, H-8), 7.92 (1H, d, J = 9, H-2 , 6 ), 7.05 (1H, d, J = 9, H-3 , 5 ), 3.82 (3H, s, 7-OCH3), 10.7 (1H, br.s, 4 -OH), 12.92 (1H, s, 5-OH). 13C NMR spectrum (125.76 MHz, DMSO-d6, , ppm): 163.75 (s, C-2), 102.82 (d, C-3), 181.56 (s, C-4), 156.92 (s, C-5), 97.70 (d, C-6), 164.81 (s, C-7), 92.43 (d, C-8), 161.01 (s, C-8a), 104.48 (s, C-4a), 120.88 (s, C-1 ), 128.25 (d, C-2 , 6 ), 115.75 (d, C-3 , 5 ), 160.95 (s, C-4 ), 55.90 (s, C-9). The mass spectrum of 1 showed a peak for a molecular ion with m/z 284.2 [M]+. Compound 1 was isolated earlier from other Artemisia species, e.g., A. capillaris Thunb., A. lessingiana Bess., A. sacrorum Ledeb., and A. pontica L. [6, 7]. An analysis of spectral data (PMR and 13C NMR) suggested that isolated compound 2 was the flavonoid 5,7-dihydroxy4 -methoxyflavone (acacetin). 5,7-Dihydroxy-4 -methoxyflavone (acacetin) (2). 1H NMR spectrum (300 MHz, DMSO-d6, , ppm, J/Hz): 6.8 (1H, s, H-3), 6.18 (1H, d, J = 2, H-6), 6.45 (1H, d, J = 2, H-8), 7.98 (1H, d, J = 9, H-2 , 6 ), 6.92 (1H, d, J = 9, H-3 , 5 ), 3.82 (3H, s, 7-OCH3), 12.88 (1H, s, 5-OH). 13C NMR spectrum (125.76 MHz, DMSO-d6, , ppm): 162.98 (s, C-2), 103.33 (d, C-3), 181.42 (s, C-4), 157.07 (s, C-5), 98.71 (d, C-6), 163.93 (s, C-7), 93.83 (d, C-8), 162.00 (s, C-8a), 103.60 (s, C-4a), 122.63 (s, C-1 ), 127.99 (d, C-2 , 6 ), 113.60 (d, C-3 , 5 ), 162.00 (s, C-4 ), 55.39 (s, C-9). The mass spectrum of 2 showed a peak for a molecular ion with m/z 284.2 [M]+. Compound 2 was isolated earlier from A. filifolia Torrey, A. gmelinii Weber ex Stechm, A. herba-alba Asso, and A. judaica L. [7]. Thus, the flavonoids genkwanin and acacetin were isolated for the first time from the aerial part of A. santolinifolia as a result of the chemical study.