Flavonoids from the Aerial Part of Alhagi persarum of the Flora of Uzbekistan and Their Biological Activity

Abstract

Dried and ground aerial part of Alhagi persarum (2.0 kg) was extracted (5×) at room temperature with EtOH (70%). The combined aqueous EtOH extract was concentrated to 0.5 L, diluted with hot H2O (1:1), and back-extracted sequentially with CHCl3 (5 × 400 mL), EtOAc (5 × 400 mL), and n-BuOH (6 × 400 mL).
The EtOAc fraction was chromatographed over a column of silica gel using gradient elution by CHCl3–MeOH in various proportions. Rechromatography of the separate eluates over Sephadex LH-20 using elution by MeOH–H2O (8:2) isolated five pure flavonoids (1–5). A comparison of spectral data of the isolated compounds (UV, IR, NMR) with the literature and a direct comparison with authentic samples identified them as naringenin (1), isorhamnetin (2), isomyricetin (3), narcissin (4) and genistin (5).
Thus, the phytochemical studies isolated for the first time from the aerial part of A. persarum compounds 1 and 3–5. Flavonols narcissin (4) and its aglycon isorhamnetin (2) are produced in major amounts in practically all plant species of the genus Alhagi and are chemotaxonomic markers.
The pharmacological studies showed that total flavonoids isolated from the aerial part of A. persarum exhibited both antioxidant properties in in vitro tests and antihypoxic activity (determined under acute normobaric hypoxia and hemic hypoxia conditions).
The results showed that total flavonoids from the aerial part of A. persarum exhibited pronounced antihypoxic activity as compared to rutin and luteolin and prolonged the lifespan of animals by 30.8–42.6%.
The lifespan increase of animals under hemic hypoxia conditions after administering the compounds was 27.0–51.0%. Their inhibitory effect on lipid peroxidation in in vitro tests was from 66.7 to 77.0% in practically the same range as the antioxidant activity. Total flavonoids from the aerial part of A. persarum were the most active. Their activity was comparable to that of the reference drug vitamin E (85.0%).

Full text

7290009-3130/20/5604-0729 ©2020 Springer Science+Business Media, LLC
Chemistry of Natural Compounds, Vol. 56, No. 4, July, 2020
FLAVONOIDS FROM THE AERIAL PART OF Alhagi persarum
OF THE FLORA OF UZBEKISTAN AND
THEIR BIOLOGICAL ACTIVITY
S. Z. Nishanbaev,1,2* Kh. M. Bobakulov,1,2 D. A. Narbutaeva,1
S. F. Aripova,1 Z. A. Khushbaktova,1 and N. D. Abdullaev1
Previously, volatile compounds in the hexane and C6H6 extracts and the compositions of essential oils obtained by
steam- and hydrodistillation from the aerial part of Alhagi persarum Boiss. & Buhse (Fabaceae) collected during full flowering
were analyzed by us using GC-MS. Also, mono- and sesquiterpenoids and their derivatives, aldehydes, and hydrocarbons and
their functional derivatives were identified [1–3].
Quercetin, isorhamnetin, quercetin-3-O-
α
-L-rhamnopyranoside, quercetin-3-O-
α
-L-arabinofuranoside, quercetin-
5,3′,4′-trimethoxy-3-O-
β
-D-galactopyranosido-(2→1)-
α
-L-rhamnopyranosido-7-O-
α
-L-rhamnopyranoside, isorhamnetin-3-
O-
β
-D-glucopyranoside, and isorhamnetin-3-O-
α
-L-arabinopyranoside were isolated from a population of A. persarum growing
in Kazakhstan [4]. Also, the polysaccharide composition of this plant was studied [5]. However, phenolic compounds from
A. persarum have not until now been studied.
The dried aerial part of A. persarum (Fabaceae) collected in June 2016 during full flowering in Jizzakh Oblast,
Republic of Uzbekistan, was studied. The species was determined by Cand. N. Yu. Beshko, Institute of Botany, AS, RUz.
Dried and ground aerial part of A. persarum (2.0 kg) was extracted (5×) at room temperature with EtOH (70%).
The combined aqueous EtOH extract was concentrated to 0.5 L, diluted with hot H2O (1:1), and back-extracted sequentially
with CHCl3 (5 × 400 mL), EtOAc (5 × 400 mL), and n-BuOH (6 × 400 mL).
The EtOAc fraction (20 g) was chromatographed over a column (3.0 × 115 cm) of silica gel using gradient elution by
CHCl3–MeOH in various proportions (10:1, 9:1, 7:1, 5:1, 3:1, 1:1). Rechromatography of the separate eluates over Sephadex
LH-20 using elution by MeOH–H2O (8:2) isolated five pure flavonoids (1–5). A comparison of spectral data of the isolated
compounds (UV, IR, NMR) with the literature and a direct comparison with authentic samples identified them as naringenin
(1, 68 mg), isorhamnetin (2, 210 mg), isomyricetin (3, 88 mg), narcissin (4, 230 mg), and genistin (5, 103 mg).
Naringenin (1), C15Í12Î5, mp 250–251°Ñ. UV spectrum (Ñ2Í5ÎÍ, λmax, nm): 290 and 326 (sh). IR spectrum (KBr,
ν, cm–1): 3410–3114 (ÎÍ), 3282 (phenolic OH), 1631 (Ñ=Î
γ
-pyrone), 1602, 1519 (Ñ=Ñ), 1312, 1250 (Ñ–Î), 1157, 1083,
1013, 889, 832. 1Í NMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.62 (1Í, dd, J = 17.1, 3.0, Í-3a), 3.21 (1Í, dd,
J = 17.1, 12.8, Í-3e), 5.37 (1Í, dd, J = 12.8, 3.0, Í-2), 5.83 (2Í, br.s, H-6, 8), 6.74 (2Í, d, J = 8.6, Í-3′, 5′), 7.26 (2Í, d,
J = 8.6, Í-2′, 6′), 9.65 (1Í, br.s, ÎÍ), 12.01 (1Í, s, 5-ÎÍ). 13C NMR spectrum (100 MHz, DMSO-d6, δ, ppm): 78.59 (C-2),
42.11 (C-3), 196.54 (C-4), 163.63 (C-5), 95.96 (C-6), 166.83 (C-7), 95.14 (C-8), 163.08 (C-9), 101.89 (C-10), 129.00
(C-1′), 128.53 (C-2′, 6′), 115.32 (C-3′, 5′), 157.85 (C-4′).
Isolated compound 1 was identified as 5,7,4′-trihydroxyflavanone (naringenin) (1) [6], which is widely distributed
among flavonoids from plants of the genus Alhagi [7].
Isorhamnetin (2), C16Í12Î7, mp 303–305°Ñ. UV spectrum (Ñ2Í5ÎÍ, λmax, nm): 255, 266, 370. IR spectrum
(KBr, ν, cm–1): 3450 (ÎÍ), 2927 (ÎÑÍ3), 1667 (>Ñ=Î), 1605, 1575, 1518 (ArÍ), 842, 817. Compound 2 was identified as
3,5,7,4′-tetrahydroxy-3′-methoxyflavonol [8].
1) S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan,
Tashkent, e-mail: sabir78@rambler.ru; 2) Tashkent Institute of Irrigation and Agricultural Mechanization Engineers, 39 Kary
Niyazov St., Tashkent, 100000, Uzbekistan. Translated from Khimiya Prirodnykh Soedinenii, No. 4, July–August, 2020,
pp. 628–629. Original article submitted January 6, 2020.
DOI 10.1007/s10600-020-03132-w

730
Isomyricetin (3), C15Í12Î5, mp 250–252°Ñ. UV spectrum (Ñ2Í5ÎÍ, λmax, nm): 258, 366. IR spectrum (KBr, ν,
cm–1): 3529–3182 (ÎÍ), 3301 (phenolic OH), 1654 (
α
,
β
-unsaturated CO), 1602, 1562, 1493 (Ñ=Ñ), 1320, 1251, 1201 (Ñ–Î),
1158, 1067, 1042, 996, 857. 1Í NMR spectrum (400 MHz, DMSO-d6, δ, ppm, J/Hz): 2.98–3.31 (5H, m, Í-2′′, 3′′, 4′′, 5′′, 6′′à),
3.55 (1Í, br.d, J = 11.4, 6′′b), 4.22, 4.91, 5.05, 5.16 (1Í each, br.s, ÎÍ), 5.42 (1Í, d, J = 7.7, H-1′′), 6.14 (1Í, d, J = 2.1, H-6),
6.32 (1Í, d, J = 2.1, H-8), 7.14 (2Í, s, H-2′, 6′), 9.13, 10.81 (1Í each, br.s, ÎÍ), 12.61 (1Í, s, 5-ÎÍ). 13C NMR spectrum
(100 MHz, DMSO-d6, δ, ppm): 156.23 (C-2), 133.52 (C-3), 177.44 (C-4), 161.30 (C-5), 98.67 (C-6), 164.13 (C-7),
93.39 (C-8), 156.30 (C-9), 104.01 (C-10), 120.09 (C-1′), 108.57 (C-2′, 6′), 145.42 (C-3′, 5′), 136.68 (C-4′), 100.90
(C-1′′), 73.96 (C-2′′), 76.62 (C-3′′), 69.97 (C-4′′), 77.71 (C-5′′), 61.15 (C-6′′) [9].
Narcissin (4), Ñ28Í32Î16, mp 179–180°Ñ. UV spectrum (Ñ2Í5ÎÍ, λmax, nm): 257, 360. IR spectrum (KBr, ν,
cm–1): 3380 (ÎÍ), 2938 (ÎÑÍ3), 1655 (Ñ=Î), 1605, 1508 (Ñ=Ñ), 1358, 1210, 1060.
Compound 4 was identified as isorhamnetin-3-O-
β
-D-rutinoside, which was isolated previously from Alhagi canescens
(Regel) B.Keller & Shap. [8].
Genistin (5), Ñ21Í20Î10, mp 253–254°C. UV spectrum (Ñ2Í5ÎÍ, λmax nm): 235, 264, 305. IR spectrum (KBr, ν,
cm–1): 3424, 2927 (ÎÍ), 1657 (Ñ=Î
γ
-pyrone), 1620, 1575, 1513 (Ñ=Ñ) and 1179, 1075, 1048 (Ñ–Î). 1Í NMR spectrum
(400 MHz, DMSO-d6, δ, ppm, J/Hz): 3.10–3.70 (6H, m, Í-2′′, 3′′, 4′′, 5′′, 6′′), 4.87 (1Í, d, J = 7.1, H-1′′), 6.17 (1Í, d, J = 2.1,
H-6), 6.33 (1Í, d, J = 2.1, H-8), 7.05 (2Í, d, J = 8.7, H-3′, 5′), 7.44 (2Í, d, J = 8.7, H-2′, 6′), 8.31 (1Í, s, H-2), 12.85 (s, 5-ÎÍ).
13C NMR spectrum (100 MHz, DMSO-d6, δ, ppm): 154.44 (C-2), 121.95 (C-3), 180.09 (C-4), 162.04 (C-5), 99.18 (C-6),
164.66 (C-7), 93.86 (C-8), 157.67 (C-9), 104.44 (C-10), 124.31 (C-1′), 130.15 (C-2′, 6′), 116.12 (C-3′, 5′), 157.34 (C-4′),
100.37 (C-1′′), 73.31 (C-2′′), 76.70 (C-3′′), 69.77 (C-4′′), 77.12 (C-5′′), 60.76 (C-6′′).
Compound 5 was identified as genistein-7-O-
β
-D-glucopyranoside [10].
Thus, the phytochemical studies isolated for the first time from the aerial part of A. persarum compounds 1 and 3–5.
Flavonols narcissin (4) and its aglycon isorhamnetin (2) are produced in major amounts in practically all plant species of the
genus Alhagi and are chemotaxonomic markers.
The pharmacological studies showed that total flavonoids isolated from the aerial part of A. persarum exhibited both
antioxidant properties in in vitro tests and antihypoxic activity (determined under acute normobaric hypoxia and hemic hypoxia
conditions [11]).
The results showed that total flavonoids from the aerial part of A. persarum exhibited pronounced antihypoxic activity
as compared to rutin and luteolin and prolonged the lifespan of animals by 30.8–42.6% (Table 1).
The lifespan increase of animals under hemic hypoxia conditions after administering the compounds was
27.0–51.0%. Their inhibitory effect on lipid peroxidation in in vitro tests was from 66.7 to 77.0% in practically the same range
as the antioxidant activity. Total flavonoids from the aerial part of A. persarum were the most active. Their activity was
comparable to that of the reference drug vitamin E (85.0%).
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TABLE 1. Antihypoxic Activity of Total Flavonoids from the Aerial Part of Alhagi persarum as Compared to Rutin and
Luteolin (M ± m, n = 6)
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Rutin, 100 mg/kg 19.0 ± 1.202* 33.4 11.0 ± 0.36 * 33.0
Luteolin, 100 mg/kg 18.6 ± 1.12* 30.8 10.5 ± 0.39 * 27.0
______
*Statistically significant vs. corresponding control for p < 0.05.

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