Chemical Constituents Of Pterocarya Tonkinesis And Their Antitumor Activity

Pterocarya tonkinesis (Franch.) Dode. (Juglandaceae) forms a typical communityof riverside season rain forest in Xishuangbanna area of Yunnan province, China. Ithas been used as a folk medicine for treatment of certain cancers by local people ofChina. Only few reports of the chemical constituents and their biological activities ofthis plant have been found up to now. According to early work of our group, thealcoholic extract of P. tonkinesis was found to possess strong activities of inducingapoptosis and necrosis in mammalian cancer cells. Thus, we have undertaken aninvestigation on its chemical constituents and their anti-tumor activity.The pilot experiment showed that the chloroform and ethyl acetate extracts werethe active ingredients of P. tonkinesis. Thus, the pulverized dry stems/barks (5.0 kg) ofP. tonkinesis were extracted at room temperature with 80% aqueous alcohol to give anaqueous alcohol solution, which was evaporated under reduced pressure to removealcohol and then extracted with the same volume of chloroform to afford an activechloroform extract (282 g).A part (62 g) of the chloroform extract was chromatographed repeatedly on silicagel, polyamide and Sephadex LH-20, followed by PTLC and PHPLC purification, togive compounds 1~8. Their structures were investigated by spectroscopic methods(MS, UV, IR, 1D NMR and 2D NMR). Eventually, the possible structure of 1 couldbe deduced as (1,2,3,4-tetrahydro-1,5-dihydroxy-2-isopropylnaphthalen-8-yl)(1,2-di-hydro-1,5-dihydroxy-2-isopropylnaphthalen-8-yl)methanone (1) and the structure of 4was determined as (4R)-4,5-dihydroxy-3,4-dihydro-1(2H)-naphthalenone (4) (Fig. 1).The other compounds could be identified as glochidone (2), lup-20(29)-en- 1β,3β-diol(3), methyl protocatechuate (5), 4-hydroxymethyl-2-methoxyphenol (6), octadecadi-enoic acid ethyl ester (7) andβ-sitosterol (8) respectively, as shown in Fig.1.Among them, 1 and 4 are new compounds, 2, 3 and 5~7 are isolated from thegenus Pterocarya for the first time, and 8 is isolated from P. tonkinesis for the firsttime.The anti-tumor activity for 1~8 was evaluated by the MTT method accompanied with the morphological observation of the cells under light microscope using humanleukemia carcinoma K562 cells. Among the compounds tested, 1, 3 and 5~7 showedto a different extent the anti-tumor activity against K562 cells. Compound 1 exhibiteda quite strong apoptosis-inducing activity, while 3, 5, 6 and 7 showed inhibitoryeffects on the proliferation of K562 cells, among which 3 showed the highest activitywith the IC50 value of 6.4μg/mL. The anti-tumor activity for 1 and 4 is the first reportof their biological activity.In the present study, eight compounds 1~8 were isolated from P. tonkinesis andtheir structures were investigated by modern spectroscopic methods to elucidatestructures of two new compounds 1 and 4 and to identify the known compounds 2, 3and 5~8. Furthermore, the results of present bioassay have indicated that 1, 3 and 5~7showed anti-tumor effects on K562 cells to a different extent. Present result hasprovided two new compounds 1 and 4 from P. tonkinesis.