in industrial quantities
Xanthohumol is a natural flavonoid extracted from the hop. The beneficial activity of this compound in the human body is staggeringly broad. Xanthohumol is an excellent antioxidant. It delays aging, increases vigor and is highly effective against fungi, bacteria, viruses and cancer.
In ORAC (Oxygen Radical Absorbance Capacity) tests, Xanthohumol achieved a score four times greater than pure vitamin C. Antiproliferative and cytotoxic activity of Xanthohumol were tested in vitro in the treatment of breast cancer (MCF-7), colon cancer (HT-29) and ovarian carcinoma (A-2780). Xanthohumol inhibits the growth of a fibrosarcoma and induces apoptosis in prostate cancer cells. It aids the conversion of cholesterol in the body (slows down oxidation of low-density lipoprotein), which reduces the risk of coronary heart diseases. It also exhibits antiviral, antimalarial and antibacterial activity. Xanthohumol effectively acts as a natural pharmaceutics in the infections associated with HIV-1.
Xanthohumol (XN, 3′-[3,3-dimethylallyl]-2′,4′,4-trihydroxy-6′-methoxychalcone) is a prenylated flavonoid derived from the female flowers of the hops plant (Humulus lupulus L), with potential chemopreventive and antineoplastic activities . Xanthohumol has been shown to inhibit the growth of different types of human cancer cells, including breast, colon, ovarian, pancreatic cancer cells and leukemia cells [2, 3, 4]. Upon administration, xanthohumol scavenges reactive oxygen species (ROS), thereby preventing DNA damage due to oxidative stress. In addition, xanthohumol is able to increase the expression of phase II cytoprotective enzymes, thereby inactivating carcinogens. This agent exerts anti-inflammatory activity, through the inhibition of inflammation-inducing enzymes, inhibits DNA synthesis, and induces apoptosis of susceptible cancer cells. Furthermore, xanthohumol might prevent transformation of mammary epithelial cells in mammary organ culture by inhibition of carcinogen-induced and mammotrophic hormone-promoted proliferation at the level of DNA synthesis . Xanthohumol also decreases the expression of C-X-C chemokine receptor 4 (CXCR4), thereby preventing cancer cell invasion .
XN was first isolated from hop in 1913 by Power et al and its structure was first identified in 1957 by Verzele et al. . However, the beneficial pharmacological properties of XN were not appreciated until 1990s, including antioxidant, anti-inflammatory, antibacterial, antiviral, antifungal, and antiplasmodial activity . In recent years, increasing evidences of XN chemopreventive in vitro potential, with an exceptional broad spectrum of inhibitory mechanisms at the initiation, promotion, and progression stages of carcinogenesis . Consistent with the anti-initiating potential, xanthohumol potently modulates the activity of enzymes involved in carcinogen metabolism and detoxification, e.g. CYP450-enzymes  and quinone reductases . Moreover, xanthohumol has been found capable of scavenging reactive oxygen species including hydroxyl and peroxyl radicals [9; 10] and of inhibiting superoxide anion radical and nitric oxide production , a causative factor for both tumor initiation and promotion . Zhao and co-workers have demonstrated that a XN at concentration of 5 µg/mL is enough for the inhibition of 80% of the production of NO induced by LPS/IFN- gamma RAW 264.7 tumor cell line . As potential anti-tumour promoting activity, xanthohumol demonstrates anti-inflammatory properties by inhibition of cyclooxygenase-1 and cyclooxygenase-2 activity . Antiproliferative mechanisms to prevent carcinogenesis in the progression phase include inhibition of DNA synthesis and induction of cell cycle arrest in the S-phase, apoptosis, and induction of cell differentiation . In vitro, xanthohumol showed a dose-dependent antileukemic activity at micromolar concentrations with IC50of 10 and 5.4 μmol/L at 48 and 72 h, respectively, whereas even smaller dose, i.e. 2.5 μmol/L, inhibited leukemic cell invasion through extracellular matrix and adhesion to endothelial cells . Furthermore, xanthohumol proved efficient at nanomolar concentrations in preventing carcinogen-induced preneoplastic lesions in mouse mammary gland organ culture, a model that serves as a link between short-term in vitro and long-term in vivo carcinogenesis models . Apart from in vitro studies, the in vivo animal study showed that administration of Xn in drinking water to CCA bearing mice can reduce tumor growth [13, 1].
During the course of anticancer activity studies, the effect of XN on normal cells was simultaneously investigated. XN exhibited very low or no toxicity in normal cells including human lung fibroblast cells (MRC-5), primary human hepatocytes, oligodendroglia-derived cells (OLN-93), and human skin fibroblasts [14; 15; 16]. These findings suggested that XN specifically targeted cancer cells, on the other hand, XN may be a safe and effective agent. Similar results were obtained in vivo .
From the findings summarized in the preceding paragraphs, we cautiously conclude that xanthohumol and other hop prenylflavonoids have potential as cancer chemopreventive agents by interfering with a variety of cellular mechanisms at low micromolar concentrations . In addition, XN has been shown to have a low toxicity profile and potent bioavailability, and orally administered xanthohumol does not affect major organ function in vivo [3; 18].
Xanthohumol and other flavonoids are non-essential products in the process of beer brewing. They largely remain behind in the residue left after extraction of the desired compounds from hops with liquid or supercritical CO.sub.2. In normal brewing conditions, whereby either whole hops, hop products, or particular hop fractions are used, the total concentration of prenylated flavonoids may be up to 4 mg per litre of beer . Beer is the alcoholic beverage of choice in many parts of the world and may represent a vehicle for increasing the consumption of natural products with antioxidant and other health-promoting properties . Based on the health-promoting properties of xanthohumol, increasing the concentration of this compound in beer might be beneficial . The potential health-maintaining effects of xanthohumol as a ‘broad-spectrum’ cancer chemopreventive agent combined with low toxicity have led to the development of experimental beers with high levels of xanthohumol (ca. 5 mg/L) . Another route would be to increase prenylflavonoid levels in hops through breeding or metabolic engineering of their biosynthesis. Genetic transformation of hops has been reported .
Xanthohumol can be obtained as a waste product of the hop processing industry by various methods. Several methods of xanthohumol extraction are described in the recent patent literature.
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