Flavonoids from Pulicaria vulgaris and Their Antimicrobial Activity
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FLAVONOIDS FROM Pulicaria vulgaris AND THEIR ANTIMICROBIAL ACTIVITY
A. Sh. Zhanzhaxina,1 M. Seiilgazy,2 R. I. Jalmakhanbetova,1* M. Yu. Ishmuratova,3 T. M. Seilkhanov,2 M. Oyama,4 Z. S. Sarmurzina,5 Zh. B. Tekebayeva,5 and Ye. M. Suleimen1,2*
Pulicaria vulgaris (prostrata) is an annual plant with numerous branched reddish stems and small (6–12 mm) yellow flowerheads. It grows on moist and salty shores of rivers and lakes and valley meadows in almost all regions of Central Asia [1]. Previously, buddledin C was isolated from essential oil of this plant [2]. The goal of the present work was to study the constituent composition of the EtOH and CHCl3 extracts of P. vulgaris and to determine the biological activity of the isolated compounds. Raw material was collected in August 2019 in the vicinity of Stary Koluton village, Astrakhan District, Akmola Province. The dried aerial part (1 kg) was extracted (3×) with EtOH for 30 min at room temperature with ultrasound and then left overnight. The extract was filtered and concentrated under vacuum to produce a dry solid (76.6 g, 7.66%). The extract was separated by column chromatography over silica gel with elution by hexane–Me2CO (gradient from 20:1 to 0:1) to produce 190 fractions and then by MeOH. The six flavonoids quercetagetin 3,7,3′-trimethyl ether (1) [3]; quercetagetin 3,7,3′,4′-tetramethyl ether (2) [4]; quercetin 3,7,3′-trimethyl ether (3) [5]; sorbifolin (4) [6]; 6-hydroxyluteolin 7,3-dimethyl ether (5) [7]; and ladanein (6) [8] were isolated from various fractions. 5,6,4′-Trihydroxy-3,7,3′-trimethoxyflavone (1) (quercetagetin 3,7,3′-trimethyl ether), yellow powder (340 mg), mp 219–220°C. HR-ESI-MS, m/z 359.0743 [M – H]– (calcd for C18H15O8, 359.0766). 1Í NMR spectrum (500 MHz, CDCl3, δ, ppm, J/Hz): 12.41 (1H, s, 5-OH), 7.69 (1H, s, H-2′), 7.66 (1H, d, J = 8.4, H-6′), 7.04 (1H, d, J = 8.4, H-5′), 6.54 (1Í, s, H-8), 6.01 (1H, s, 4′-OH), 5.33 (1H, s, 6-OH), 4.01 (3H, s, 3′-OCH3), 3.99 (3H, s, 7-OCH3), 3.85 (3H, s, 3-OCH3). 13C NMR spectrum (125 MHz, CDCl3, δ, ppm): 156.31 (C-2), 138.77 (C-3), 178.84 (C-4), 145.36 (C-5), 129.27 (C-6), 152.96 (C-7), 90.26 (C-8), 149.84 (C-9), 106.45 (C-10), 122.72 (C-1′), 111.00 (C-2′), 146.44 (C-3′), 148.40 (C-4′), 114.67 (C-5′), 122,72 (C-6′), 60.28 (3-OCH3), 56.22 (7-OCH3), 56.59 (3′-OCH3). COSY: H-5′→H-6′, H-6′→H-5′. HSQC: H-8→Ñ-8, H-2′→Ñ-2′, H-5′→Ñ-5′, H-6′→C-6′, 3-OCH3→3-OCH3, 7-OCH3→7-OCH3, 3′-OCH3→3′-OCH3. HMBC: H-8→C-6, C-7, C-9, Ñ-10; H-2′→Ñ-4′, C-6′; H-5′→Ñ-1′, C-3′; H-6′→Ñ-2′, Ñ-4′; 3-OCH3→C-3; 7-OCH3→C-7; 3′-OCH3→C-3′; 5-OH→C-5, Ñ-6, C-10; 6-OH→C-5, C-6, C-7; 4′-OH→C-4′, C-5′ [3]. 5,6-Dihydroxy-3,7,3′,4′-tetramethoxyflavone (2) (quercetagetin 3,7,3′,4′-tetramethyl ether), brown crystals (9 mg), mp 204–205°C. HR-ESI-MS, m/z 373.0927 [M – H]– (calcd for C19H17O8, 373.0923). 1Í NMR spectrum (500 MHz, CDCl3, δ, ppm, J/Hz): 12.41 (1H, s, 5-OH), 7.72 (1H, dd, J = 2.5, 8.6, H-6′), 7.67 (1H, d, J = 1.8, H-2′), 6.98 (1H, d, J = 8.6, H-5′), 6.55 (1Í, s, H-8), 3.99 (3H, s, OCH3), 3.97 (3H, s, OCH3), 3.96 (3H, s, OCH3), 3.86 (3H, s,
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