Chemical Constituents and Biological Activities of Dicranopteris linearis

Abstract

The genus Dicranopteris (Gleicheniaceae) consists of about 10 species, distributed mainly in Asia. Several species of this genus are used as traditional medicines throughout the world [1]. The whole plant of Dicranopteris linearis is used commonly for the treatment of internal heat or fever, asthma, external wound, ulcers, and broils as a folk medicine in China [2]. Previously, the extracts of D. linearis have been reported to possess antinociceptive, anti-inflammatory, antipyretic, and cytotoxic activities [3, 4]. Aiming to find potentially bioactive secondary metabolites from this species, we investigated the whole plant of D. linearis and isolated 10 known compounds (1–10), in which compounds 1–6 were isolated from it for the first time. All these compounds were tested for antibacterial activities against five bacteria and cytotoxic activities against two selected cancer cells. Within the series of compounds tested, compounds 7–10 exhibited moderate activities against Escherichia coli, Bacillus cereus, Staphyloccocus aureus, Erwinia carotovora, and Bacillus subtilis with MICs ranging from 15.5 to 62.5 g/mL. Moreover, compound 7 showed the strongest activity against HL-60 and SMMC-7721 with IC50 values of 4.5 and 9.0 g/mL, respectively. To the best of our knowledge, this is the first report that the isolated compounds from D. linearis show antibacterial and cytotoxic activities. Plant Material. The whole plants of D. linearis were collected from Jianfengling of Hainan Province, China, in August 2007 and were identified by Senior Engineer Qiong-Xin Zhong at the Department of Biology, Hainan Normal University, China. A voucher specimen (No. 2007806) was deposited at the Natural Organic Academy of Lanzhou University. Extraction and Isolation. Air-dried whole plants (8.6 kg) of D. linearis were extracted three times (each for 7 days) with 90% ethanol (20 L) at room temperature. The ethanol filtrates were collected and concentrated under reduced pressure by a rotary evaporator at 40 C to provide 415 g of ethanol extract. The extract was suspended in water and partitioned with petroleum ether (PE), EtOAc, and n-BuOH, followed by concentration to yield 55 g of the petroleum ether extract, 80 g of EtOAc extract, 95 g of the n-BuOH extract, and 185 g of the water extract. The EtOAc extract (80 g) was subjected to silica gel column chromatography (200–300 mesh, 400 g) with a gradient of PE–EtOAc (30:1, 15:1, 8:1, 4:1, 2:1, 1:1) as eluent, and five fractions (Fr.1.1–Fr.1.5) were collected according to TLC analysis. Fraction 1.2 (1.2 g) was further separated on a silica gel column (200–300 mesh, 3 g) eluting again with PE–EtOAc (15:1) to provide compound 3 (8 mg). Fraction 1.3 (3.1 g) on the silica gel column eluting with PE–EtOAc (8:1) gave compounds 1 (6 mg) and 2 (5 mg). The n-BuOH extract (95 g) was applied to an HP20 column (1000 mL) with a gradient of H2O–EtOH (5:0, 4:1, 3:2, 2:3, 1:4, 0:5) as eluent, and six fractions (Fr.2.1–Fr.2.6) were collected according to TLC analysis. Fraction 2.3 (3.0 g) was chromatographed through a column of reversed-phase C18 silica gel eluting with MeOH–H2O (2:1) to afford compounds 4 (3 mg), 5 (2 mg), and 6 (3 mg). The separation of fraction 2.5 (8.7 g) was done on a silica gel column (200–300 mesh, 87 g) with a gradient of CHCl3–MeOH (8:1, 4:1, 2:1, 1:1) as the eluent, and three fractions were collected according to TLC analysis. Then the CHCl3–MeOH elution fraction (4:1, 100 mg) was further separated on a silica gel column (200–300 mesh, 3 g) eluting again with CHCl3–MeOH (8:1) to give compound 7 (20 mg). The CHCl3–MeOH fraction (2:1, 200 mg) was separated on a silica gel column (200–300 mesh, 1.5 g) eluting with CHCl3–MeOH (4:1) to afford compound 8 (7 mg). Further separation of the CHCl3–MeOH fraction (4:1, 100 mg) on a reversed-phase C18 silica gel column eluting with MeOH–H2O (1:2) gave compounds 9 (10 mg) and 10 (14 mg).