Betulinic acid
Encyclopedia
Betulinic acid is a naturally occurring pentacyclic triterpenoid
which has anti-retroviral
, anti-malaria
l, and anti-inflammatory
properties, as well as a more recently discovered potential as an anticancer agent, by inhibition of topoisomerase
. It is found in the bark
of several species of plants, principally the white birch (Betula pubescens) from which it gets its name, but also the Ber
tree (Ziziphus mauritiana), selfheal (Prunella vulgaris
), the tropical carnivorous plants Triphyophyllum peltatum and Ancistrocladus heyneanus
, Diospyros leucomelas
a member of the persimmon
family, Tetracera boiviniana
, the jambul (Syzygium formosanum
), flowering quince (Chaenomeles sinensis
),
Rosemary
,
and Pulsatilla chinensis.
of human melanoma
.
Then it was demonstrated, that betulinic acid induces apoptosis
in human melanoma in vitro
and in vivo
model systems. Currently it is undergoing development with assistance from the Rapid Access to Intervention Development program of the National Cancer Institute
.
Also betulinic acid was found active against neuroectodermal (neuroblastoma
, medulloblastoma
, Ewing's sarcoma) and malignant brain tumors, ovarian carcinoma, in human leukemia
HL-60 cells, malignant head and neck squamous cell carcinoma SCC25 and SCC9 cell lines.
In contrast, epithelial tumors, such as breast carcinoma, colon carcinoma, small cell lung carcinoma and renal cell carcinoma
as well as T-cell leukemia
cells were completely unresponsive to treatment with betulinic acid.
of betulinic acid, little is known about its antiproliferative and apoptosis
-inducing mechanisms. In neuroectodermal tumor cells betulinic acid–induced apoptosis is accompanied by caspase
activation, mitochondrial membrane alterations and DNA
fragmentation. Caspases are produced as inactive proenzymes, which are proteolytically processed to their active forms. These proteases can cooperate in proteolytic cascades, in which caspases activate themselves and each other. The initiation of the caspases cascade may lead to the activation of endonuclease
s like caspase-activated DNAase (CAD). After activation CAD contributes to DNA degradation.
Betulinic acid induces apoptosis by direct effects on mitochondria, leading to cytochrome-c release, which in turn regulates the "downstream" caspase activation.
Betulinic acid bypasses resistance to CD95 and doxorubicin
-mediated apoptosis, due to different molecular mechanism of betulinic acid-induced apoptosis.
Controversial is a role of p53
in betulinic acid-induced apoptosis. Fulda suggested p53-independent mechanism of the apoptosis, basing on fact of no accumulation of wild-type p53 detected upon treatment with the betulinic acid, whereas wild-type p53 protein strongly increased after treatment with doxorubicin. The suggestion is supported by study of Raisova. On the other hand Rieber suggested that betulinic acid exerts its inhibitory effect on human metastatic melanoma partly by increasing p53.
The study also demonstrated preferential apoptotic effect of betulinic acid on C8161 metastatic melanoma cells, with greater DNA fragmentation and growth arrest and earlier loss of viability than their non-metastatic C8161/neo 6.3 counterpart.
Comparing the betulinic acid with other treatment modes, Zuco demonstrated that it was more than 10 times less potent than doxorubicin (IC50 4.5 μg/ml Vs IC50 0.21-034 μg/ml in doxorubicin) [I think the original author has a missing decimal point in the expression 0.21-034 μg/ml. I think it should be 0.21-0.34 μg/ml. Could somebody check his references to find out if I am correct] and showed an in vitro antiproliferative activity against melanoma and non-melanoma cell lines, including those resistant to doxorubicin. On the human normal dermatoblast cell line betulinic acid was 2-5 times less toxic than doxorubicin.
The ability of betulinic acid to induce two different effects (cytotoxic and cytostatic) on two clones derived from the same human melanoma metastasis suggests that the development of clones resistant to this agent will be more unlikely, than that to conventional cytotoxic drugs. Moreover in spite of the lower potency compared with doxorubicin, betulinic acid seems to be selective for tumor cells with minimal toxicity against normal cells. The effect of betulinic acid on melanoma cell lines is stronger than its growth-inhibitory effect on primary melanocytes. Study of combination of betulinic acid with γ-irradiation showed clearly additive effects, and indicates that they differ in their mode of action.
and methyl betulinate were less active on human melanoma than betulinic acid. Moreover, some C-28 amino acids and C-3 phthalates derivatives exhibited higher cytotoxic activity against cancer cell lines with improved selective toxicity and water solubility. Chatterjee and co-workers obtained the 28-O-β-D-glucopyranoside of betulinic acid by microbial transformation with Cunninghamella species while Baglin and co-workers obtained it by organic synthesis. This glucoside did not exhibit any significant in vitro activity on human melanoma (MEL-2) and human colorectal adenocarcinoma (HT-29) cell lines which confirms the importance of the carboxylic acid function to preserve the cytotoxicity. Recently, Gauthier and coworkers have synthesized a series of 3-O-glycosides of betulinic acid which exhibited a strongly potent in vitro anticancer activity against human cancer cell lines.
A source of soluble and ingestible betulinic acid (and its precursor, betulin
) is the Chaga
(Inonotus Obliquus) a slow growing medicinal fungus that is found as a parasite on birch trees in the coldest regions of the northern hemisphere. This mushroom converts the betulin present in the bark of the birch into a soluble and ingestible form of betulinic acid. Using a proper extraction protocol (alcohol/ethanol extraction) will make the compounds available for oral consumption. The slow growing pattern of the fungus (7-10 years minimum) and the fact that it cannot be cultivated without losing most of its properties do make this an unreliable source, though.
Triterpenoid
Triterpenoids are terpenoid derviatives of triterpene molecules.They may have useful anti-cancer properties.Notable examples*Betulinic acid, possible anti-cancer drug*Bardoxolone methyl, inflammation modulator*Triterpenoid saponins...
which has anti-retroviral
Retrovirus
A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome. The DNA is then incorporated into the host's genome by an integrase enzyme. The virus thereafter replicates as part of the host cell's DNA...
, anti-malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
l, and anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
properties, as well as a more recently discovered potential as an anticancer agent, by inhibition of topoisomerase
Topoisomerase
Topoisomerases are enzymes that regulate the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double helical structure. For example, during DNA replication, DNA becomes overwound ahead of a replication fork...
. It is found in the bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
of several species of plants, principally the white birch (Betula pubescens) from which it gets its name, but also the Ber
Ziziphus mauritiana
Ziziphus mauritiana, also known as Jujube, Chinee Apple, Indian plum, and permseret , is a tropical fruit tree species belonging to the family Rhamnaceae....
tree (Ziziphus mauritiana), selfheal (Prunella vulgaris
Prunella vulgaris
Prunella vulgaris, known as common selfheal, heal-all, heart-of-the-earth, is a medicinal plant in the genus Prunella. It grows 5 to 30 cms high , with creeping, self-rooting, tough, square, reddish stems branching at leaf axis...
), the tropical carnivorous plants Triphyophyllum peltatum and Ancistrocladus heyneanus
Ancistrocladus
Ancistrocladus is a little known genus of about 20 species in the monogeneric family Ancistrocladaceae.These are palaeotropical climbing twining plants, found in lowland to submontane, wet to seasonal evergreen or swamp forests, with eleven species occurring in tropical Africa and at least five...
, Diospyros leucomelas
Diospyros
Diospyros is a genus of about 450–500 species of deciduous and evergreen trees. The majority are native to the tropics, with only a few species extending into temperate regions. They are commonly known as ebony or persimmon trees...
a member of the persimmon
Persimmon
A persimmon is the edible fruit of a number of species of trees in the genus Diospyros in the ebony wood family . The word Diospyros means "the fire of Zeus" in ancient Greek. As a tree, it is a perennial plant...
family, Tetracera boiviniana
Dilleniaceae
Dilleniaceae is the botanical name for a family of flowering plants. Such a family has been universally recognized by taxonomists. It is known to gardeners for the genus Hibbertia, which contains many commercially valuable garden species....
, the jambul (Syzygium formosanum
Syzygium
Syzygium is a genus of flowering plants that belongs to the myrtle family, Myrtaceae. The genus comprises about 1100 species, and has a native range that extends from Africa and Madagascar through southern Asia east through the Pacific...
), flowering quince (Chaenomeles sinensis
Chaenomeles
Chaenomeles is a genus of three species of deciduous spiny shrubs, usually 1–3 m tall, in the family Rosaceae. They are native to eastern Asia in Japan, China and Korea...
),
Rosemary
Rosemary
Rosemary, , is a woody, perennial herb with fragrant, evergreen, needle-like leaves and white, pink, purple or blue flowers, native to the Mediterranean region. It is a member of the mint family Lamiaceae, which includes many other herbs, and is one of two species in the genus Rosmarinus...
,
and Pulsatilla chinensis.
Anti-tumor activity
In 1995, betulinic acid was reported as a selective inhibitorEnzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
of human melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
.
Then it was demonstrated, that betulinic acid induces apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
in human melanoma in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
and in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
model systems. Currently it is undergoing development with assistance from the Rapid Access to Intervention Development program of the National Cancer Institute
National Cancer Institute
The National Cancer Institute is part of the National Institutes of Health , which is one of 11 agencies that are part of the U.S. Department of Health and Human Services. The NCI coordinates the U.S...
.
Also betulinic acid was found active against neuroectodermal (neuroblastoma
Neuroblastoma
Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an annual incidence of about 650 cases per year in the US , and 100 cases per year in the UK . Close to 50 percent of neuroblastoma cases occur in children younger than two years old...
, medulloblastoma
Medulloblastoma
Medulloblastoma is a highly malignant primary brain tumor that originates in the cerebellum or posterior fossa.Previously, medulloblastomas were thought to represent a subset of primitive neuroectodermal tumor of the posterior fossa...
, Ewing's sarcoma) and malignant brain tumors, ovarian carcinoma, in human leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
HL-60 cells, malignant head and neck squamous cell carcinoma SCC25 and SCC9 cell lines.
In contrast, epithelial tumors, such as breast carcinoma, colon carcinoma, small cell lung carcinoma and renal cell carcinoma
Renal cell carcinoma
Renal cell carcinoma is a kidney cancer that originates in the lining of the proximal convoluted tubule, the very small tubes in the kidney that filter the blood and remove waste products. RCC is the most common type of kidney cancer in adults, responsible for approximately 80% of cases...
as well as T-cell leukemia
T-cell leukemia
T-cell leukemia describes several different types of lymphoid leukemia which affect T cells.Types include:* Large granular lymphocytic leukemia* Adult T-cell leukemia/lymphoma* T-cell prolymphocytic leukemia...
cells were completely unresponsive to treatment with betulinic acid.
Mode of action
Regarding the mode of actionMode of action
Historically, pesticides have often been classified according to their chemical groups and this is useful for understanding the properties of a given compound. However, it is the Mode of Action group which possibly represents the most useful pesticide classification for biologists...
of betulinic acid, little is known about its antiproliferative and apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
-inducing mechanisms. In neuroectodermal tumor cells betulinic acid–induced apoptosis is accompanied by caspase
Caspase
Caspases, or cysteine-aspartic proteases or cysteine-dependent aspartate-directed proteases are a family of cysteine proteases that play essential roles in apoptosis , necrosis, and inflammation....
activation, mitochondrial membrane alterations and DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
fragmentation. Caspases are produced as inactive proenzymes, which are proteolytically processed to their active forms. These proteases can cooperate in proteolytic cascades, in which caspases activate themselves and each other. The initiation of the caspases cascade may lead to the activation of endonuclease
Endonuclease
Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain, in contrast to exonucleases, which cleave phosphodiester bonds at the end of a polynucleotide chain. Typically, a restriction site will be a palindromic sequence four to six nucleotides long. Most...
s like caspase-activated DNAase (CAD). After activation CAD contributes to DNA degradation.
Betulinic acid induces apoptosis by direct effects on mitochondria, leading to cytochrome-c release, which in turn regulates the "downstream" caspase activation.
Betulinic acid bypasses resistance to CD95 and doxorubicin
Doxorubicin
Doxorubicin INN is a drug used in cancer chemotherapy. It is an anthracycline antibiotic, closely related to the natural product daunomycin, and like all anthracyclines, it works by intercalating DNA....
-mediated apoptosis, due to different molecular mechanism of betulinic acid-induced apoptosis.
Controversial is a role of p53
P53
p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer...
in betulinic acid-induced apoptosis. Fulda suggested p53-independent mechanism of the apoptosis, basing on fact of no accumulation of wild-type p53 detected upon treatment with the betulinic acid, whereas wild-type p53 protein strongly increased after treatment with doxorubicin. The suggestion is supported by study of Raisova. On the other hand Rieber suggested that betulinic acid exerts its inhibitory effect on human metastatic melanoma partly by increasing p53.
The study also demonstrated preferential apoptotic effect of betulinic acid on C8161 metastatic melanoma cells, with greater DNA fragmentation and growth arrest and earlier loss of viability than their non-metastatic C8161/neo 6.3 counterpart.
Comparing the betulinic acid with other treatment modes, Zuco demonstrated that it was more than 10 times less potent than doxorubicin (IC50 4.5 μg/ml Vs IC50 0.21-034 μg/ml in doxorubicin) [I think the original author has a missing decimal point in the expression 0.21-034 μg/ml. I think it should be 0.21-0.34 μg/ml. Could somebody check his references to find out if I am correct] and showed an in vitro antiproliferative activity against melanoma and non-melanoma cell lines, including those resistant to doxorubicin. On the human normal dermatoblast cell line betulinic acid was 2-5 times less toxic than doxorubicin.
The ability of betulinic acid to induce two different effects (cytotoxic and cytostatic) on two clones derived from the same human melanoma metastasis suggests that the development of clones resistant to this agent will be more unlikely, than that to conventional cytotoxic drugs. Moreover in spite of the lower potency compared with doxorubicin, betulinic acid seems to be selective for tumor cells with minimal toxicity against normal cells. The effect of betulinic acid on melanoma cell lines is stronger than its growth-inhibitory effect on primary melanocytes. Study of combination of betulinic acid with γ-irradiation showed clearly additive effects, and indicates that they differ in their mode of action.
Anticancer derivatives
A major inconvenience for the future clinical development of betulinic acid and analogues resides in their poor solubility in aqueous media like blood serum and polar solvents used for bioassays. To circumvent this problem of hydrosolubility and to enhance pharmacological properties, many derivatives were synthesized and evaluated for cytotoxic activity. A study showed that C-20 modifications involve the loss of cytotoxicity. Another study demonstrated the importance of the presence of the COOH group since compounds substituted at this position like lupeolLupeol
Lupeol is a pharmacologically active triterpenoid found in a variety of plants, including mango and acacia visco. It has several medicinal properties, one being anti-inflammatory...
and methyl betulinate were less active on human melanoma than betulinic acid. Moreover, some C-28 amino acids and C-3 phthalates derivatives exhibited higher cytotoxic activity against cancer cell lines with improved selective toxicity and water solubility. Chatterjee and co-workers obtained the 28-O-β-D-glucopyranoside of betulinic acid by microbial transformation with Cunninghamella species while Baglin and co-workers obtained it by organic synthesis. This glucoside did not exhibit any significant in vitro activity on human melanoma (MEL-2) and human colorectal adenocarcinoma (HT-29) cell lines which confirms the importance of the carboxylic acid function to preserve the cytotoxicity. Recently, Gauthier and coworkers have synthesized a series of 3-O-glycosides of betulinic acid which exhibited a strongly potent in vitro anticancer activity against human cancer cell lines.
A source of soluble and ingestible betulinic acid (and its precursor, betulin
Betulin
Betulin is an abundant naturally occurring triterpene. It is commonly isolated from the bark of birch trees and forms up to 30% of the dry weight of the extractive . The purpose of the compound in the bark is not known...
) is the Chaga
Chaga mushroom
Inonotus obliquus, commonly known as Chaga mushroom , is a fungus in Hymenochaetaceae family. It is parasitic on Birch and other trees. The sterile conk is irregularly formed and has the appearance of burnt charcoal...
(Inonotus Obliquus) a slow growing medicinal fungus that is found as a parasite on birch trees in the coldest regions of the northern hemisphere. This mushroom converts the betulin present in the bark of the birch into a soluble and ingestible form of betulinic acid. Using a proper extraction protocol (alcohol/ethanol extraction) will make the compounds available for oral consumption. The slow growing pattern of the fungus (7-10 years minimum) and the fact that it cannot be cultivated without losing most of its properties do make this an unreliable source, though.
See also
- Oleanolic acidOleanolic acidOleanolic acid or oleanic acid is a naturally occurring triterpenoid, widely distributed in food and medicinal plants, related to betulinic acid. It can be found in Phytolacca americana , and Syzygium spp, garlic, etc...
- Moronic acidMoronic acidMoronic acid is a natural triterpene. Moronic acid can be extracted from Rhus javanica, a sumac plant traditionally believed to hold medicinal applications...
- Franziska B. Mullauer, Jan H. Kessler, Jan Paul Medema Betulin Is a Potent Anti-Tumor Agent that Is Enhanced by Cholesterol, 2009