Chemical Constituents of Ajania nematoloba

Abstract

Ajania nematoloba (Hand.-Mazz.) Y. Ling & C. Shih, a species of Ajania from the Asteraceae family, is distributed mainly in the northwest of China, and many species of Ajania are used as folk medicinal plants for curing bronchitis, lung diseases, intestinal ulcers, and rheumatism [1]. The chemical constituents of this plant have not yet been reported. In the course of screening for biologically and chemically novel agents in the Asteraceae family, we investigated this plant. Fifteen compounds were isolated from the whole plants of A. nematoloba, and some of the constituents showed significant antitumor and antioxidant activities. The specimen of A. nematoloba was collected in September from Lanzhou, Gansu Province, China and identified by Prof. Guoliang Zhang of Lanzhou University. A voucher specimen is deposited in the Laboratory of Natural Products Chemistry, Fujian Medical University of Fujian Province. The air-dried and powdered whole plants of A. nematoloba (4.5 kg) were cut into small pieces and refluxed three times with 95% ethanol at room temperature for 7 days each time. The ethanol extract was concentrated to an aqueous residue, which was extracted successively with petroleum ether, ethyl acetate, and n-butanol. Each fraction was purified by column chromatography with silica gel, Sephadex LH-20, and RP-18 to yield 1–15. The structures of the isolated compounds were identified on the basis of spectroscopic analyses including 1H, 13C NMR spectroscopy, and mass spectrometry. The 15 compounds were determined as luteolin-7-O-D-glucopyranoside (1) [2], acacetin-7-O-D-glucopyranoside (2) [3], eriodictyol-7-O-D-glucopyranoside (3) [4], 3 -methoxyluteolin-7-OD-glucopyranoside (4) [5], luteolin (5) [2], apigenin (6) [2], cirsilineol (7) [6], jaceosidin (8) [7], centaureidin (9) [8], baihuaqianhuside (10) [9], 5 ,8 -epidioxyergosta-6,22-dien-3 -ol (11) [10], (22E,24R)-ergosta-7,22-dien-3 ,5 ,6 -triol (12) [10], palmitic acid (13) [11], daucosterol (14), and -sitosterol (15). All these compounds were isolated from A. nematoloba for the first time. Cytotoxicities of compounds 1–3, 5, and 7–9 were tested on the three cancer cell lines: human leukemia cells K562, human colon cancer cells Colon26, and human colon cancer cells SW1116. Table 1 shows that 7 exhibited significant cytotoxicity against K562, Colon26, and SW1116, with IC50 values of 6.7, 6.9, and 6.4 g/mL, respectively. The radical-scavenging activity of compounds 1–5, 8, and 9 against DPPH free radical were measured, and compounds 1 and 3–5 showed excellent antioxidant activity (Fig. 1).