Hop (Humulus lupulus) is a plant which contains many bitter chemicals. Hops contain weak acids which have many actions, such as anticancer, antioxidant, anti-angiogenesis, apoptotic and detoxification. They are anti-inflammatory and work against diabetes mellitus, cardiovascular disease and the metabolic syndrome. Ninety percent of hops go to the brewing industry.
Female hop plants form cones in the summer which secrete a yellow resinous powder called lupulin from glands. Lupulin contains polyphenols, bitter acids and volatile oils. Hop research has been primarily on the polyphenols. Hop bitter acids are 30% of lupulin. Extracts and oils of hops are used for flavoring, brewed and non-brewed beverages and in foods. The German Commision E monograph describes hop use for mood and sleep problems.
Hop acids are alpha-acids (humulones) or beta-acids (lupulones). Alpha-acids in beer improve foam stability, reduce gushing, add bitter taste and prevent microorganism growth. Alpha-acids may be responsible for the “lightstruck” beer taste. Vitamin B-2 (riboflavin) stimulates the light-stimulated reaction of alpha-acids breaking down into chemicals responsible for the “skunky” taste of stale beer. Beta-acids don’t add a bitter taste.
The chemical components of hop bitter acids have therapeutic potential for cancer treatment. They help treat cancer by inducing apoptosis (a natural form of cell death). Humulone induces apoptosis in promyeloid leukemia cells. Hop acids have low bioavailability when taken by mouth.
The growth and cell division (proliferation) of cancer cells are inhibited by hop bitter acids. Active chemical components are lupulone, colupulone and semisynthetic hexahydrocolupulone. Inhibition of proliferation is believed to inhibit cancer growth. Humulone reduces proliferation in human leukemia cells.
Angiogenesis (growth of new capillary blood vessels) is necessary for growth in cancers. Vascular endothelial growth factor (VEGF) is a protein produced by cancer cells which promotes angiogenesis. Humulone inhibits angiogenesis and reduces levels of VEGF in vitro. Nitric oxide is important in VEGF production, also. An extract of hops with lupulone inhibits nitric oxide production.
There is a cellular detoxification enzyme system called the cytochrome P-450 system. Lupulone in a mouse diet will increase the P-450 enzymes in the liver to promote detoxification. Further research of this activity of hops bitter acids is needed.
Hop was used by Native Americans (Delawares) as an anti-inflammatory. Humulone is more anti-inflammatory than nonsteroidal indomethacin and less active than the steroid hydrocortisone. Cycloxygenases (COX) are enzymes which convert arachidonic acid to various inflammatory chemicals. Humulone inhibits COX-2 activity to reduce inflammation. Pharmaceutical COX-2 inhibitors, such as Celebrex (celecoxib), are used to treat rheumatoid arthritis and osteoarthritis. Hop acids don’t seem to relieve the symptoms of fibromyalgia.
The metabolic syndrome includes abdominal obesity, insulin resistance, abnormal glucose tolerance and insulin resistance, high blood pressure and vascular diseases. Iso-alpha-acids (derivatives of alpha-acids) have been shown to improve lipids, glucose tolerance and body weight. Hop acids increase HDL-cholesterol and reduce liver cholesterol in mice. The acids seem to prevent hypertension by increasing nitric oxide (NO) which is needed by the kidneys to maintain normal sodium balance.
Osteoporosis results from an imbalance of bone formation and bone absorption. Lupulone inhibits bone absorption. Research has shown osteoporosis to be related to inflammation. Hops acids are anti-inflammatory.
Hops reduce the excitability of the central nervous system and cause sleepiness. Hop workers report fatigue while working with hops. Hop teas and balneotherapeutics products contain degradation products of humulone and lupulone which are sedating and tranquilizing. Dragees contain large amounts of hop acids.
The antimicrobial activity of hop is primarily against gram-positive organisms such as Lactobacillus, Streptococcus, Staphylococcus, Micrococcus and Bacillus. Hops don’t work against gram-negative organisms such as Escherichia coli. Hops do not inhibit yeast growth. Hop acids inhibit the growth of tuberculosis (Mycobacterium tuberculosis) in mice. One study showed hops to be useful in human tuberculosis.
CONCLUSION: Hop bitter acids have shown potential for being anti-cancer, antibacterial, anti-inflammatory. They modulate central nervous system activity and reduce complications of the metabolic syndrome. Hop acids can be useful for cancer, diabetes mellitus, osteoarthritis, osteoporosis and cardiovascular diseases.
NOTE: Dragees are candies which are small balls with nuts or sugar centers, such as chocolate-covered almonds. Balneotherapy is bath therapy.
There are many bioactive chemicals in functional foods. Read about bioactive chemicals in fish protein which reduce hypertension.
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PMID: 19476340.
Summary #315.
