鉅櫚.SAW PALMETTO
Latin name: Serenoa repens Other name: Sabal Common Names: Saw Palmetto, Sabal Origin: North American Atlantic Coast
Description: Saw Palmetto is a small palm tree with large leaves and large deep red-blackberries. The berries were used by the American Indians as a general tonic to nourish the body and encourage appetite and normal weight gain. The berries were also used in the treatment of genito-urinary tract problems including enuresis, nocturia, and urinary tract disorders. Recent clinical trials have shown that saw palmetto berries are helpful in the treatment of benign prostatic hyperplasia. Saw palmetto (Serenoa repens) is a dwarf palm tree in the family Arecaceae, which is native to the southeast region of the U.S. Atlantic coast. It grows up to six feet with 18"–30" wide leaves divided into 6–20 fan-shaped gray to bluish-green lobes. Its tiny, fragrant, cream-colored flowers are hidden among the leaves in the summer followed by egg-shaped purple-black berries. The berries of this impressive palm are gathered from September until January. From the olive-sized berries of the saw palmetto tree comes a remedy for benign enlargement of the prostate gland. While harmless, this common condition (BPH, or benign prostatic hyperplasia) can interfere with the urine's exit from the bladder, causing frequent urination, nighttime awakenings, and other uncomfortable urinary symptoms. It's not clear what causes BPH. But as the millions of men who suffer from it can attest--more than half of men over 60 are affected--relief is welcome indeed. The popularity of saw palmetto--so-named in recognition of the saw-toothed stems that lie at the base of each palm leaf--has waxed and waned over time. Until 1950, it was officially recognized in the United States as a drug for urinary and genital problems. But conventional American doctors eventually became disenchanted with the remedy; they could find little solid evidence to prove its effectiveness for any condition. Europeans, on the other hand, have been steadfast in their enthusiasm for the prostate-healing gifts of this scrubby, native American palm tree (also known as Serenoa repensor S. serrulata). Herbalists worldwide have also recommended saw palmetto as a general tonic and remedy for persistent cough and digestive problems. Plant Description: Saw palmetto is a fan palm that can reach heights of 10 feet in warm climates. In the United States, it grows in the warm climates of the southeast, from South Carolina to Mississippi and throughout Florida. Lush, green leaves fan out from thorny stems. The plant bears white flowers, which develop yellow olive-like berries. The berries, when ripe, turn bluish-black and are dried for medicinal use.
Chemical Composition: Analysis of the 95% ethanol extract of the berries for the known lipid content showed fatty acids, fatty acid esters, and phytosterols. Fatty Acids: Free fatty acid composition is rich in shorter chain length fatty acids such as capric, caprylic, lauric and myristic acid. Additionally, the extract contains palmitic, stearic, oleic, linoleic and linolenic acid. A small portion of the fatty acids are found in the ester form, mainly in ethyl-ester. Phytosterols: The following sterols have been identified in the alcoholic extract: campesterol, stigmasterol, ß-sitosterol and cycloartenol. Other chemical constituents identified in the berries include aliphatic alcohols (C26-30), polyprenic compounds, flavonoids, glucose, galactose, arabinose, uronic acid and other polysaccharides. The actual active ingredient in the berries, however, remains undetermined. Saw palmetto's active ingredients include fatty acids, plant sterols, and flavonoids. However, most likely these are not the only substances within the berries that affect hormone production, and it will take more scientific study to determine exactly how saw palmetto works. The berries also contain high-molecular-weight polysaccharides, which are usually associated with either anti-inflammatory or immune-stimulant effects. Recently, a number of clinical trials have confirmed the effectiveness of saw palmetto in treating BPH. Many of these trials have shown saw palmetto works better than the most commonly used prescription drug, Proscar. Saw palmetto is effective in nearly 90% of patients after six weeks of use, while Proscar is effective in less than 50% of patients. In addition, Proscar may take up to six months to achieve its full effect. Since Proscar blocks the production of testosterone, it can cause impotence and breast enlargement. Also, saw palmetto is significantly less expensive than Proscar. A one month supply of saw palmetto costs $12-25, while a one month supply of Proscar costs $65-75. Other prescription drugs used to treat BPH are Cardura (doxazosin), Hytrin (terazosin), and Flomax (tamsulosin hydrochloride). Originally prescribed to treat hypertension, Cardura and Hytrin can drop blood pressure, causing lightheadedness and fainting. Presently, saw palmetto is being evaluated by the U.S. Food and Drug Administration (FDA) for treatment of BPH. If approved, it would become the first herbal product to be licensed by the agency as a treatment for a specific condition. Saw palmetto is listed in the Physicians Desk Reference for Herbal Medicine (1998 Edition) as a treatment for prostate complaints and irritable bladder. Since the 1960s, extensive clinical studies of saw palmetto have been done in Europe. A review of 24 European trials appeared in the November 1998 issue of the Journal of the American Medical Association. The trials involved nearly 3,000 men, some taking saw palmetto, others taking Proscar, and a third group taking a placebo. The men taking saw palmetto had a 28% improvement in urinary tract symptoms, a 24% improvement in peak urine flow, and 43% improvement in overall urine flow. The results were nearly comparable to the group taking Proscar and superior to the men taking a placebo. Surgery represents a final solution for BPH patients. In the U.S., 350,000 surgical procedures are performed annually while an additional 1.6 million patients undergo pharmacological treatment. The phytopharmaceutical therapy of BPH includes different plant extract capsules of seeds, roots, leaves and berries that are currently available in the U.S. and are widely used in Europe for symptomatic relief. The most popular among these herbal remedies is saw palmetto. Pharmacological Properties: PHYSIOLOGY Saw Palmetto berries contain an oil with a variety of fatty acids and phytosterols. These fatty acids include capric, caprylic, caproic, lauric, palmitic, and oleic acid and their ethyl esters. The major phytosterols are beta-sitosterol, stigmasterol, cycloartenol, stigmasterol, cycloartenol, lupeol, lupenone, and 24-methyl-cyclo-artenol. The fat soluble extract of saw palmetto berries has been shown to inhibit the conversion of dihydroxytestosterone (DHT) which is thought to be responsible for the enlargement of the prostate. In addition saw palmetto extract inhibits the binding of DHT to receptors thus blocking DHT's action and promoting the breakdown of the potent compound. The North American Indians used saw palmetto berries as a remedy for atrophy of the testes, impotence, inflammation of the prostate, and low libido in men. The berries are also recommended for infertility, painful periods, and lactation in women. The berries also have a traditional use as a tonic and expectorant for mucous membranes, particularly the bronchial passages.
Saw palmetto has become the sixth best-selling herbal dietary supplement in the United States (Associated Press, 1997); the standardized extract sold in health food stores comes in 160-mg capsules (Mendosa, 1997). Saw palmetto berry powder is available from the Indiana Botanical Garden, Inc. (Shimada et al., 1997). In Europe, several pharmaceutical companies sell saw palmetto-based over-the-counter (OTC) drugs for the treatment of benign prostatic hyperplasia (BPH). Pierre Fabre, a French pharmaceutical company, markets a BPH drug called Permixon® (Associated Press, 1997) while Therabel Pharma in Belgium markets a similar drug called Prostaserene® (Braeckman, 1994). The following other BPH medications contain saw palmetto extracts as one of their principal ingredients: PA109, Curbicin, Prostagalen, Prostaselect, Prostavigol, and Strogen forte (Dreikorn and Richter, 1989; cited by Lowe and Ku, 1996). Additional pharmaceutical preparations that contain saw palmetto extract as an ingredient have been patented as hair lotions for the treatment of seborrhea (excessive secretion of the sebaceous glands) (Jeanjean and Navarro, 1995) and hair loss, capsules for the treatment of hair loss (Crandall, 1996), and lotions and ointments for the treatment of acne (Fauran et al., 1996). Beta-sitosterol is available as a cholesterol-lowering drug under the name Cytellin®, manufactured by Eli Lilly and Company (Cohen and Raicht, 1981). Beta-sitosterol is the main component of Harzol, an OTC drug for the treatment of BPH (Lowe and Ku, 1996) and is available for purchase on the Internet in Prostate Support Formula, which also contains zinc, copper, pygeum, vitamin B6, pumpkin seed powder, and nettles (Anonymous, 1997d). It is also an ingredient in some contraceptive drugs. Sitosterols (as a group) are available as raw material in 50- and 200-kg fiber drums from Henkel Corporation (Strum, 1997). STRUCTURE-ACTIVITY RELATIONSHIPS: To compare the effect of beta-sitosterol and cholesterol on growth and differentiation of human prostate cancer cells, von Holtz et al. (1991) cultured the cancer cells in medium supplemented with up to 16 M sterol delivered by a cyclodextrin vehicle. Growth was measured by counting the cells in each culture on days 1, 3, and 5 of treatment, and culture media and cell lysates were assayed for total (ACP) and prostatic acid phosphatase (PAcP). Beta-sitosterol was more effective in inhibiting the growth of human prostate cancer cells than cholesterol. After 3 days of incubation with 16 M beta-sitosterol, cell growth was 72% of the cell growth of cultures treated with equimolar cholesterol. In examining the 4-M sterol groups, PAcP in the cell lysate was significantly higher in the cholesterol-treated group than in the beta-sitosterol-treated group. At the 16-M level, the concentration of PAcP remained constant in the cholesterol group and increased significantly in the beta-sitosterol-treated group, suggesting that differentiation may be involved in the inhibition of prostate cancer cell growth. Saw palmetto berries have been used in American folk medicine for several hundred years as an aphrodisiac and for treating prostate problems. Native Americans in the southeast United States have used saw palmetto since the 1700s to treat male urinary problems. In the 1800s, medical botanist John Lloyd noted that animals that ate saw palmetto appeared healthier and fatter than other livestock. Early American settlers noticed the same effects and used the juice from saw palmetto berries to gain weight, to improve general disposition, as a sedative, and to promote reproductive health. In the United States, the medicinal uses of saw palmetto were first documented in 1879 by Dr. J.B. Read, a physician in Savannah, Georgia, who published a paper on the medicinal benefits of the herb in the April 1879 issue of American Journal of Pharmacy. He found the herb useful in treating a wide range of conditions. "By its peculiar soothing power on the mucous membrane it induces sleep, relieves the most troublesome coughs, promotes expectoration, improves digestion, and increases fat, flesh and strength. Its sedative and diuretic properties are remarkable," Read wrote. "Considering the great and diversified power of the saw palmetto as a therapeutic agent, it seems strange that it should have so long escaped the notice of the medical profession." A pungent tea made from saw palmetto berries was commonly used in the early 1900s to treat prostate enlargement and urinary tract infections. It was also used in men to increase sperm production and sex drive, although these uses are discounted today. One of the first published medical recommendations that saw palmetto was effective in treating prostate problems appeared in the 1926 edition of United States Dispensatory. In the late 1920s, the use of medicinal plants, including saw palmetto, began to decline in the United States, while at the same time, it was on the rise in Europe.
beta-sitosterol
Active Substances: steroidal saponins, fatty acids, phytosterols, volatile oil, resin, tannins In Vitro Studies: Recent research has focused on comparing the inhibitory effect of Permixon on 5-a-reductase enzyme, which converts testosterone to dihydrotestosterone (DHT), to 5-a-reductase inhibitors such as finasteride and 4-MA (17-(N,N-diethyl)carbamoyl-4-methyl-4-aza-5-androstan-3-one). Finasteride and other highly specific 5-a-reductase inhibitors have been developed on the premise that the blockage of DHT synthesis leads to a reduction of prostate growth. Two isoenzymes of 5-a-reductase, types I and II, have been detected in cultured human prostate cells. While there is some controversy over which type is dominant, it is generally agreed that type II predominates and that finasteride selectively inhibits 5-a-reductase II. In vitro studies using the eukaryotic expression system demonstrated that the lipido/sterolic extract of saw palmetto inhibits both isoenzymes. Other studies have shown that Serenoa extract inhibits androgenic activity by competing with DHT for the androgen receptor, thereby affecting testosterone metabolism. The binding of two synthetic androgens, mibolerone and methyltrienolone, that are specific for androgen receptors at low concentrations (5nM), were inhibited by Serenoa extract (Permixon) in a competitive manner. Various plant steroids were tested for competitive binding to androgen receptors and found to be inactive.13,14 The inhibitory effect of Serenoa extract on DHT and testosterone binding was tested in tissue from 11 BPH patients. An average of 40%-42% reduction in receptor binding was observed for both hormones. |
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