Chemical Constituents of the Roots of Zizyphus rugosa

摘要

Zizyphus is a genus of about 40 species of spiny shrubs and small trees in the buckthorn family Rhamnaceae growing in warm-temperate and subtropical regions throughout the world. Zizyphus rugosa Lam. is a large straggling shrub with recurved prickles and is widely distributed in the Northeast part (Kalasin Province) of Thailand. It is used in the treatment of diarrhea and menorrhagia [1]. Previous phytochemical study of this plant revealed the presence of flavonoids [2], peptide alkaloids [3], and a triterpeniod saponin [4]. The isolation and purification of the CH_2Cl_2 and MeOH crude extracts of the roots of Z. rugosa led to the isolation of eight triterpeniods, lupeol (1), betulin (2) [5], betulinic aldehyde (3), betulinic acid (4) [6], alphitolic acid (5) [7], euscaphic acid (6) [8], zizyberenalic acid (7) [9], and β-sitosterol (8) [10], one coumarin, scopoletin (9) [11], and four flavonoids, kaempferol (10) [12], afzelin (11), quercitrin (12) [13], and (+)-catechin (13) [14]. The structures of all isolated compounds were identified by means of spectroscopic techniques as well as comparison with previous literature data. Compounds 1–13 were subjected to in vitro cytotoxic study against KB (human epidermoid carcinoma) and HeLa (human cervical carcinoma) cell lines using the standard colorimetric MTT method [15, 16]. Compounds 2 and 7 exhibited moderate activity against KB and HeLa cells, with IC_(50) values of 10.0 and 5.5 μg/mL and 9.5 and 13.0 μg/mL, respectively, while compound 4 showed only very modest cytotoxic activity against HeLa cells (IC_(50) = 10.0 μg/mL). On the other hand, the other compounds could be regarded as inactive (IC_(50) >30.0 μg/mL). It is worth noting that compounds 2 and 7 might be lead compounds for use as antitumor agents. The IC_(50) value of adriamycin (standard reference) in both cell lines was 0.018 μg/mL. To the best of our knowledge, this is the first report on the isolation of compounds 5, 6, 7, and 9 and on the in vitro cytotoxic study of this plant.