Some glycosides isolated from desmodium gangeticum (L.) DC. of Viet Nam

From the methanol extract of the leaves of Desmodium gangeticum collected in Me Linh, Ha Noi, we isolated 5 compounds. In which, there are four glycosides including (6S,9R)- roseoside (1), kaempferol-3-O-rutinoside (nicotiflorin) (2), quercetin-3-O-rutinoside (rutin) (3), β-sitosterol-3-O- β-D-glucopyranoside (4), and the other is protocatechuic acid (5). Kaempferol3-O-rutinoside (2) was isolated from Desmodium gangeticum for the first time while (6S,9R)- roseoside (1) was isolated from the genus Desmodium for the first time. Their structures were determined by 1D and 2D NMR spectra.
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Some glycosides isolated from desmodium gangeticum (L.) DC. of Viet NamVietnam Journal of Science and Technology 56 (2A) (2018 ) 99-103 SOME GLYCOSIDES ISOLATED FROM DESMODIUM GANGETICUM (L.) DC. OF VIET NAM Le Minh Ha1*, Ngo Thi Phuong 1, Le Ngoc Hung2, Vu Thi Hai Ha3, Bui Kim Anh4, Pham Quoc Long1 1 Institute of Natural Products Chemistry, VAST, 18 Hoang Quoc Viet, Cau Giay, Ha Noi 2 Pharmaceutical Chemistry Lab Project, Center for Research and Technology Transfer, VAST, 18 Hoang Quoc Viet, Cau Giay, Ha Noi 3 Hanoi University of Science, Vietnam National University, Ha Noi, 334 Nguyen Trai, Thanh Xuan, Ha Noi 4 Institute of Chemistry, VAST, 18-Hoang Quoc Viet, Nghia Do, Cau Giay, Ha Noi * Email: halm2vn@gmail.com Received: 11 March 2018; Accepted for publication: 14 May 2018 ABSTRACT From the methanol extract of the leaves of Desmodium gangeticum collected in Me Linh,Ha Noi, we isolated 5 compounds. In which, there are four glycosides including (6S,9R)-roseoside (1), kaempferol-3-O-rutinoside (nicotiflorin) (2), quercetin-3-O-rutinoside (rutin) (3),β-sitosterol-3-O- β-D-glucopyranoside (4), and the other is protocatechuic acid (5). Kaempferol-3-O-rutinoside (2) was isolated from Desmodium gangeticum for the first time while (6S,9R)-roseoside (1) was isolated from the genus Desmodium for the first time. Their structures weredetermined by 1D and 2D NMR spectra.Keywords: Desmodium gangeticum, (6S,9R)-roseoside, kaempferol-3-O-rutinoside, quercetin-3-O-rutinoside, β-sitosterol-3-O-β-D-glucopyranoside, protocatechuic acid. 1. INTRODUCTION Desmodium gangeticum (L.) DC. (Fabaceae) is a slightly woody perennial herb andwidely distributed in South East Asia, India and Africa. In Vietnam and other countries,D. gangeticum has been used for various purposes such as wound ulcers, snake bites, diuretic,edema, asthma, stomatitis, arthritis, eczema, hair loss, neurological disorders, prematureejaculation and to make tonic. D. gangeticum is known to be rich in flavonoids, alkaloids, sterolsand glycolipids with antioxidant, antibacterial, antidiabetic, antiulcer activities. To date, over 30compounds were found from this plant in the world [1, 2]. However, in Vietnam, very fewstudies on chemical constituents of D. gangeticum have been reported. Only two publics ofNguyen Tiet Dat et al. isolated 4 phenolic glucosides from the leaves of D. gangeticum alongwith few other researches on qualitative identification of coumarin and flavonoid. [3,4,5,6] To Le Minh Ha, Ngo Thi Phuong, Le Ngoc Hung, Vu Thi Hai Ha, Bui Kim Anh, Pham Quoc Longclearify chemical constituents of D. gangeticum Vietnam, in this paper we report the isolationand structural identification of four other glycosides such as (6S,9R)-roseoside (1), kaempferol-3-O-rutinoside (2), quercetin-3-O-rutinoside (3), β-sitosterol-3-O-β-D-glucopyranoside (4), andanother compound protocatechuic acid (5) from methanol extract of the leaves of D. gangeticum. 2. EXPERIMENTAL2.1. Plant materials The leaves of D. gangeticum were collected at Melinh, Hanoi, Vietnam in June 2017. Thescientific name was identified by Dr Bui Van Thanh, Institute of Ecology and BiologicalResources, VAST. The voucher specimen no. TL-DG20062017 is preserved at Institute ofNatural Product Chemistry, Vietnam Academy of Science and Technology.2.2. General experimental procedures The 1H-NMR (500MHz) and 13C-NMR (125MHz) spectra were recorded on a BrukerAM500 FT-NMR spectrometer and tetramethylsilane was used as an internal standard. Columnchromatography (CC) was performed using a silica gel (0.040 – 0.063 mm) and YMC RP-18resins (30 – 50 μm). Thin layer chromatography (TLC) used pre-coated silica gel 60 F254 andRP-18 F254S plates. Compounds were visualized by UV light at 254 and 365 nm, and by sprayingwith the solution of 10 % H2SO4 in ethanol and heating for 1-3 minutes.2.3. Extraction and isolation The dried leaves of D. gangeticum (1.5 kg) were powdered and extracted in turn with n-hexane, ethyl acetate, methanol at 50oC (3 times x 2 hours per time) on heated ultrasonicmachine. Filtered extracts were combined and concentrated under low pressure to give n-hexane(24 g), ethyl acetate (52 g) and methanol (85 g) extracts. The methanol extract (50 g) wasseparated on a silica gel column eluted with ethyl acetate : methanol (100:1 → 1:100, v:v) toobtain 6 fractions (M1→M6). The fraction M1 was chromatographed on a silica gel columneluted with chloroform: ...