Isolation and identification of l/d-lactate-conjugated bufadienolides from toad eggs revealing lactate racemization in amphibians

Three pairs of bufadienolide l/d-lactate epimers (1-6) were isolated from the eggs of the toad Bufo bufo gargarizans. The structures were elucidated by using spectroscopic methods, X-ray diffraction analysis and a modified Mosher's method. Compounds 1-6 represent the first occurrence of lactate...

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Bibliographic Details
Published in:Organic & biomolecular chemistry 2017-07, Vol.15 (26), p.5609-5615
Main Authors: Zhou, Shiwen, Zheng, Qingfei, Huang, Xiuyong, Wang, Yong, Luo, Sifan, Jiang, Renwang, Wang, Lei, Ye, Wencai, Tian, Haiyan
Format: Article
Language:English
Subjects:
Amphibia
Amphibians
Animals
Antineoplastic Agents - chemistry
Antineoplastic Agents - isolation & purification
Antineoplastic Agents - pharmacology
Bufanolides - chemistry
Bufanolides - pharmacology
Bufo bufo
Bufo bufo gargarizans
Cell Line, Tumor
Cell Proliferation - drug effects
Cell Survival - drug effects
Dose-Response Relationship, Drug
Drug Screening Assays, Antitumor
Humans
Lactic Acid - chemistry
Lactic Acid - isolation & purification
Lactic Acid - pharmacology
Molecular Conformation
Ovum - chemistry
Structure-Activity Relationship
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Summary:Three pairs of bufadienolide l/d-lactate epimers (1-6) were isolated from the eggs of the toad Bufo bufo gargarizans. The structures were elucidated by using spectroscopic methods, X-ray diffraction analysis and a modified Mosher's method. Compounds 1-6 represent the first occurrence of lactate-conjugated bufadienolides in nature, and illustrate the existence of an enzyme-controlled epimerization from l- to d-lactate in amphibians. The biosynthetic pathways, in which two key enzymes might be involved (i.e., lactate racemase and acyltransferase), were proposed. In addition, the biological assays revealed that compounds 1-4 are potent cytotoxic agents against human gastric cancer cells BGC-823 and human lung cancer cells A549 with IC values in a range of 8.0 to 80.0 nM.
ISSN:1477-0520
1477-0539
DOI:10.1039/c7ob01055a