Chemical Components of the Tuber of Alocasia cucullata

Abstract

Alocasia cucullata Schott is mainly distributed in Guangxi, Guangdong, Sichuan, Guizhou, and Fujian Provinces in China (Wu, 1990). Its tuber (Chinese name “jianweiyu”) is a well-known ethnic medicine of the Zhuang nationality in China and is used to treat cancer, reduce swelling, for detoxification, and to ease pain. The antitumor effects of this herb have been preliminarily confirmed because of its widespread clinical application in China for centuries. Nevertheless, up to now, no systematic study has been done on the antitumor constituents of A. cucullata, and the occurrence of an N-acetyl-D-lactosamine (LacNAc)-specific lectin has been reported in a previous investigation of A. cucullata [1]. Our previous pharmacological study further showed the presence of cytotoxic activity in a 50% ethanol extract [2]. In this article we report the isolation of a total of 12 substances: steroid (1), alkaloids (2–4), and phenolic substances (5–12) for the first time from the genus Alocasia. Plant Material. The tubers of A. cucullata were collected in Sichuang Province, China, in May 2011 and identified by Prof. Bao-Kang Huang (Second Military Medical University, Shanghai, China). A voucher specimen (Zheng 5580) has been deposited in the Herbarium of the Shanghai University of Traditional Chinese Medicine. Processing of Plant Material. The tubers of A. cucullata (5 kg) were powdered and extracted three times with 50% EtOH. The extract was concentrated under reduced pressure to give a crude residue (200 g), which was extracted successively with petroleum ether, ethyl acetate, n-butanol. The n-butanol fraction, concentrated to dryness (30 g), was further fractionated on a silica gel chromatography column (600 g of silica gel 60, 70–230 mesh; CHCl3–MeOH–H2O [(15:0.4:1,10:0.4:1, and 5:0.4:1) gradient)] to give four fractions, Frs. A, B, C, and D which were further fractionated on a silica gel chromatographic column (RP-18): CC of Fr. A (2.2 g) (RP-18, 200 g; CH3OH–H2O 4:1) gave 1 (30 mg), 2 (36 mg), 3 (30 mg), and 4 (28 mg); CC of Fr. B (6.2 g) (RP-18, 400 g; CH3OH–H2O 1:1) gave 3 (20 mg), 4 (100 mg), 5 (46 mg), 6 (30 mg), 7 (58 mg), and Fr. B (0.9 g), which were pooled. Fraction B was chromatographed on Sephadex LH-20 (CH3OH–H2O 1:1) yielding 8 (32 mg). CC of Fr. C (5.2 g) (RP-18, 400 g; CH3OH–H2O 2:1) gave 9 (30 mg) and 10 (34 mg). CC of Fr. D (2.1 g) (RP-18, 400 g; CH3OH–H2O 4:1) gave 11 (21 mg) and 12 (25 mg). Compound 1, C35H60O6, white amorphous powder (MeOH), mp 134–135 C. ESI-MS m/z 577 [M + H]+. Its physical constants and spectral data were in agreement with those of -daucosterol [3]. Compound 2, C10H13N5O4, white amorphous powder (MeOH), mp 234.4–235.4 C. ESI-MS m/z 268 [M + H] +. Its physical constants and spectral data were in agreement with those of -adenosine [4]. Compound 3, C6H6N2O, white amorphous powder (MeOH), mp 129–130 C. ESI-MS m/z 121 [M – H]–. Its physical constants and spectral data were in agreement with those of niacinamide [5]. Compound 4, C9H7NO, white gum (MeOH). ESI-MS m/z 146 [M + H] +. Its physical constants and spectral data were in agreement with those of 1H-indole-3-carboxaldehyde [5]. Compound 5, C9H10O3, yellow oil, mp 49–50 C. ESI-MS m/z 167 [M + H]+. Its physical constants and spectral data were in agreement with those of paeonol [6]. Compound 6, C7H6O5, yellow powder. ESI-MS m/z 171 [M + H] +. Its physical constants and spectral data were in agreement with those of gallic acid [6].