Xanthohumol D

Bioorg Med Chem. 2013 Apr 1;21(7):2001-6.

Fungal metabolites of xanthohumol with potent antiproliferative activity on human cancer cell lines in vitro.[Pubmed: 23434138]

Xanthohumol (1) and Xanthohumol D (2) were isolated from spent hops. Isoxanthohumol (3) was obtained from xanthohumol by isomerisation in alkaline solution.
METHODS AND RESULTS:
Six metabolites were obtained as a result of transformation of xanthohumol (1) by selected fungal cultures. Their structures were established on the basis of their spectral data. One of them: 2″-(2'''-hydroxyisopropyl)-dihydrofurano-[4″,5″:3',4']-4',2-dihydroxy-6'-methoxy-α,β-dihydrochalcone (6) has not been previously reported in the literature. The antioxidant properties of hops flavonoids and Xanthohumol Derivatives were investigated using the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. The effects of these compounds on proliferation of MCF-7, PC-3 and HT-29 human cancer cell lines were determined by the SRB assay.
CONCLUSIONS:
With the exception of one metabolite, all tested compounds showed antiproliferative activity against the tested human cancer lines. α,β-Dihydroxanthohumol (4), obtained through the biotransformation of xanthohumol, showed higher antiproliferative activity against MCF-7 human breast carcinoma cell line than cisplatin, a widely used anticancer therapeutic agent, and a comparably high activity against PC-3 human prostate cancer cell line.

Anal Chem. 2005 Oct 1;77(19):6407-14.

Screening method for the discovery of potential cancer chemoprevention agents based on mass spectrometric detection of alkylated Keap1.[Pubmed: 16194107]

Natural products are important sources of drugs such as cancer chemopreventive agents, but most assays for the discovery of compounds in natural product extracts are low throughput and provide little information about lead compounds in these complex mixtures. The induction of enzymes such as quinone reductase, glucuronyl transferases, glutathione S-transferases, and sulfotransferases can protect cells against the toxic and neoplastic effects of carcinogens. An increase in the concentration of Nrf2 in the nucleus of a cell upregulates the antioxidant response element and induces the expression of these chemopreventive enzymes.
METHODS AND RESULTS:
Based on the hypothesis that ubiquitination and proteosome-mediated degradation of Nrf2 in the cytoplasm decreases upon the covalent modification of 1 or more of the 27 cysteine sulfhydryl groups on Keap1 (a protein that sequesters Nrf2 in the cytoplasm) and results in higher Nrf2 levels both in the cytoplasm and in the nucleus, a high-throughput mass spectrometry-based screening assay was designed to detect alkylation of sulfhydryl groups of human Keap1. As an initial high-throughput screening step, matrix-assisted laser desorption time-of-flight mass spectrometry was used to determine whether incubation of Keap1 with a botanical sample produced adducts of Keap1. Test extracts found to form adducts with Keap1 were then incubated with the alternative biological nucleophile glutathione and characterized using LC-UV-MS-MS. After validation of the assay using two model alkylating agents, fractions of an extract of hops (Humulus lupulus L.) from the brewing industry were screened, and several compounds were detected as potential chemopreventive agents.
CONCLUSIONS:
Two of these electrophilic hops constituents were identified as xanthohumol and Xanthohumol D. In a subsequent cell-based assay, xanthohumol and Xanthohumol D were confirmed to be potent inducers of quinone reductase, and reaction with Keap1 was also confirmed. Therefore, this new mass spectrometric screening assay was demonstrated to facilitate the discovery of chemoprevention agents in complex natural product mixtures.