Contents lists available at ScienceDirect Phytochemistry Letters journal homepage: www.elsevier.com/locate/phytol Two new compounds and α-glucosidase inhibitors from the leaves of Bidens pilosa L. Truong Van Nguyen Thien, Vi Ha Thi Huynh, Loan Kieu Thi Vo, Nhan Trong Tran, Thuat My Luong, Tho Huu Le, Toan Phan Duc, Quang Ton That ⁎ Faculty of Chemistry, VNUHCM—University of Science, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam ARTICLE INFO Keywords: Bidens pilosa L. Asteraceae Caffeoylquinic acid α-Glucosidase inhibitor ABSTRACT From the leaves of Bidens pilosa L., the n-hexane, chloroform, and aqueous extracts exhibited in vitro α- glucosidase inhibitory activity, with IC 50 values of 235.8, 125.6, and 100.3 μg/mL, respectively. Two new compounds, methyl 4-O-caffeoyl-2-C-methyl-D-erythronate (1) and 4-O-methylokanin (2), and seven known compounds were isolated from these extracts. The chemical structures of 1–9 were elucidated on the basis of NMR spectroscopic analysis. The caffeoylquinic acid derivatives were isolated from the aqueous extract, and showed significant α-glucosidase inhibitory activity with IC 50 values ranging from 10.7 to 74.7 μM. 1. Introduction Bidens pilosa L., belonging to Asteraceae is a perennial herb and an esculent plant (Bartolome et al., 2013) and grows wild in Vietnam. All parts of this herb have been used as the traditional medicine for inflammation, immunological disorders, digestive disorders, infectious diseases, cancers, metabolic syndrome, and wounds (Bartolome et al., 2013). Previously, many polyacetylenes, flavonoids, caffeoylquinic and p-coumaric acid derivatives, sesquiterpenes, pheophytins have been reported (Xuan and Khanh, 2016). Moreover, B. pilosa was used as the treatment of type I and type II diabetes mellitus (Connelly, 2009). The aqueous extract of this herb was evaluated the activity on type II diabetes (Hsu et al., 2009; Ubillas et al., 2000). In the process of screening on Vietnamese medicinal plants for treatment of diabetes mellitus (Dang et al., 2014, 2015), the α-glucosidase inhibitory activity has been evaluated to find the active extracts and compounds (Van de Laar et al., 2005). Herein, a bioactivity-guided fractionation was carried out, leading to the isolation of two new compounds, methyl 4-O-caffeoyl-2-C- methyl-D-erythronate (1) and 4-O-methylokanin (2). The structures of seven known compounds (3–9) were identified as centaureidin (3) (Barberá et al., 1986), jaceidin (4)(Flamini et al., 2001), 3-O-caffeoyl- 2-C-methyl-D-erythrono-1,4-lactone (5)(Ogawa and Sashida, 1992), methyl 3,4-di-O-caffeoylquinate (6)(Liu et al., 2013), methyl 4,5-di-O- caffeoylquinate (7)(Chen et al., 2014), methyl-3,5-di-O-caffeoylquinate (8)(Liu et al., 2013), methyl 5-O-E-caffeoylquinate (9)(Lee et al., 2013). The methanol residue, all extracts, and isolated compounds were evaluated the α-glucosidase inhibitory activity. This is the first report about the α-glucosidase inhibitory activity of the leaves extract from Bidens pilosa L. 2. Results and discussion The dried powder of the leaves of Bidens pilosa was exhaustively extracted with methanol. The methanol residue was fractionated into the n-hexane, chloroform, and aqueous extracts. Further separation and purification of the chloroform and aqueous extracts led to the isolation of two new compounds (1 and 2) and seven known compounds (3–9). Compound 1 was obtained as a yellowish liquid with an optical activity of α [ ] D 25 -14 (c 0.02, MeOH). The HR-ESI-MS spectrum, acquired in the positive mode, showed a sodiated molecular ion peak at m/z 349.0878 [M+Na] + (calcd for C 15 H 18 O 8 Na, 349.0899). The 1 H NMR spectrum showed an ABX aromatic system [δ H 6.77 (1H, d, J = 8.2 Hz, H-5′), 6.98 (1H, dd, J = 8.2, 2.0 Hz, H-6′), and 7.03 (1H, d, J = 1.9 Hz, H-2′)], two olefinic protons [δ H 6.20 (1H, d, J = 15.9 Hz, H-8′), and 7.47 (1H, d, J = 15.9 Hz, H-7′)], one methylene group [δ H 4.05 (1H, dd, J = 11.1, 7.6 Hz, H-4a) and δ H 4.13 (1H, dd, J = 11.1, 4.2 Hz, H-4b)], one oxygenated methine proton [δ H 3.89 (1H, m, H-3)], one methoxy group [δ H 3.63 (3H, s, H-6)], and one methyl group [δ H 1.28 (3H, s, H-5)] (Table 1). The 13 C NMR and HSQC spectra displayed the signals of two carbonyl carbons [δ C 174.9 (C-1) and 166.5 (C-9′)], two oxygenated aromatic carbons [δ C 148.5 (C-4′) and 145.2 (C-3′)], one aromatic quaternary carbon [δ C 125.5 (C-1′)], three aromatic methine carbons [δ C 121.4 (C-6′), 115.9 (C-5′), and 114.7 (C-2′)], two http://dx.doi.org/10.1016/j.phytol.2017.04.015 Received 9 February 2017; Accepted 13 April 2017 ⁎ Corresponding author. E-mail address: ttquang@hcmus.edu.vn (Q.T. That). Phytochemistry Letters 20 (2017) 119–122 1874-3900/ © 2017 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved. MARK