Glycosylation of Glaucocalyxin a and Evaluation of Its Cytotoxic Activity
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GLYCOSYLATION OF GLAUCOCALYXIN A AND EVALUATION OF ITS CYTOTOXIC ACTIVITY
Zhaobao Xiang,1,2* Yan Zhang,2 Yongsheng Jin,3 Bin Sun,1,2 and Gang Chen1,2
The 7,14-diglucoside of glaucocalyxin A was prepared by a five-step reaction. Its structure was confirmed by spectroscopic methods, and its cytotoxic activity was tested by the MTT method. Keywords: glaucocalyxin A, 7,14-diglucoside of glaucocalyxin A, cytotoxic activity. Glaucocalyxin A (GLA) [7α,14β-dihydroxy-ent-kaur-16-en-3,15-dione] is a natural ent-kaurane diterpenoid with an α-methylene cyclopentanone structure isolated from Isodon japonica (Burm.f) Hara var. galaucocalyx (Maxim.) Hara, which is especially abundant in the Northern part of P. R. China. It has been used as anticancer, antimastitis, and antiarthralgia agents in folk medicine [1]. GLA has attracted considerable attention in recent years because of its pharmacological activities such as cytotoxicity and antitumor activity [2, 3], anticoagulative activity [4], antithrombotic activity [5, 6], immune-enhancing activity [7], antineuroinflammatory activity [8], and antioxidant activity [9]. Among them, studies on its cytotoxicity is of vital significance [10] because of the prevalence of tumor diseases [11]. Carbohydrates are an essential structural component of living cells and participate in many biological activities: the immunological response, infection mechanisms, signal transduction, inammation, cell differentiation, and so on [12]. In natural products, the activities of the active ingredients are related to the existence of glucose. During the process of glycosylation, the conformation of the molecule is modified to improve its solubility and orientation and ultimately to increase its affinity and capacity as a biological receptor, such as glucose-aspirin, steviolbioside, stearylamide, and glycosylated cucurbitacins [13]. However, glycosidation of natural compounds is very difficult. At present, little research has been done on the enhancement of antitumor activity of ent-kaurane diterpenoid by glycosidation. In order to compare the antitumor activity of diterpenoid and its glycoside derivatives, glycosylation of glaucocalyxin A was accomplished and its cytotoxic activity examined. p-Tolyl thio-2,3,4,6-tetra-O-benzoyl-3-D-glucopyranoside (4) was obtained by the procedure shown in Scheme 1; the percentage after the number of the substance is the yield. a
O
HO HO
OAc
OAc
OH OH
AcO AcO
OAc
OBz c
O AcO AcO
OAc
OH 1
b
O
ST ol OAc
O BzO BzO
3, 85%
2, 96%
ST ol OBz 4, 86%
a. Ac2O; b. TolSH–BF3⋅EtO, DCM, 0°C; c. 1. NaOMe–MeOH, 2. BzCl–Py–DAMP
Scheme 1
1) Key Laboratory of Natural Medicine Research of Chongqing Education Commission, Chongqing Technology and Business University, 400067, Chongqing, P. R. China; 2) College of Environment and Resources, Chongqing Technology and Business University, 400067, Chongqing, P. R. China; 3) School of Pharmacy, Second Military Medical University, 200433, Shanghai, P. R. China. Published in Khimiya Prirodnykh Soedinenii, No. 5, September–October,
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