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Cucurbitane glucosides from the root of Machilus yaoshansis
Maoluo Gan1, Mingtao Liu, Bo Liu
1State Key Laboratory of Bioactive Substance and Function of Natural Medicines, and Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China.
Abstract:
Seven new cucurbitane triterpene glucosides (1-5, 8, and 9) and five known analogues (6, 7, 10, cucurbitacin I 2-O-β-d-glucopyranoside, and khekadaengoside K) have been isolated from an ethanol extract of roots of Machilus yaoshansis. Compounds 1 and 2 have an unusual 16,23:22,25-diepoxy unit, 4 is an uncommon cucurbitane 25-carbamate with the carbamoyl amino group attached at C-24 to form an oxazolidinone ring in the side chain, and 8 is the first example of a trinorcucurbitane derivative. The configurations in several pairs of C-24 epimeric cucurbitacins with 24,25-dihydroxy-22-one side chains were assigned, and the validity of J(23a,24) and J(23b,24) values to differentiate the configuration at C-24 in these cucurbitane derivatives is discussed. Compounds 2-4 showed in vitro activity against protein tyrosine phosphatase 1B with IC50 values of 8.63, 2.81, and 4.26 μM, respectively. Cucurbitacin E 2-O-β-d-glucopyranoside (10) showed selective cytotoxicity against BGC-823 and A549 cancer cells with IC50 values of 4.98 and 3.20 μM, respectively.
