Saw Palmetto
» Saw Palmetto consists of partially dried, ripe fruit of Serenoa repens (Bartram) Small (Fam. Arecaceae) [Serenoa serrulatum Schultes; Sabal serrulata (Michaux) Nichols].
Packaging and storage— Preserve in tight containers, protected from light.
Labeling— The label states the Latin binomial and, following the official name, the part of the plant contained in the article.
Botanic characteristics—
Macroscopic— Subspherical to ovoid drupes, about 2 to 3 cm in length and about 1.5 cm thick, dark brown to black with a smooth, dull surface and with large, irregular depressions and ridges caused by shrinkage on drying; remains of style at the summit; base bearing a small depression with the scar of the stalk; epicarp and underlying sarcocarp forming a fragile layer that partially peels off, revealing the hard, pale brown layer of endocarp surrounding the seed. Seed irregularly spherical to ovoid, up to about 1.2 cm in length and 1 cm in width, hard, surface finely pitted and reddish brown with a paler, raised and membranous area over the raphe and micropyle; when cut transversely, it shows a thin testa, a narrow perisperm, and a large area of dense, horny, grayish-white endosperm.
Microscopic— The pulp is covered by a small-celled, thin-walled epidermis and consists chiefly of a very large-celled, mostly thin-walled parenchyma. The outermost layers contain brown substances; farther inside, single cells only with brown contents are scattered in the tissue; occasional large, thick-walled, rather punctate stone cells with a wide lumen are also found. The vascular bundles are accompanied by fibers with cover cells (stigmata) containing siliceous solids attached. The innermost layers of the pulp wall consist of almost completely thickened, rather punctate, quite irregularly shaped stone cells (astrosclereids). The outer layers of the seed coat are large-celled, the cells are coarse-walled; the middle layers are thin-walled, the cells are smaller; the innermost layers are small-celled, flattened. All cells are filled with a brown substance. On the outside, the endosperm exhibits radial elongated, nonpunctate, coarse-walled cells; in the deeper layers, the cells are larger, thick-walled, rather coarse punctate. The middle lamella is fairly recognizable. Aleurone with protein crystalloids is present in the cell contents.
Identification— [note—Perform the following test under subdued light.]
Reagent solution— Transfer 37.0 mg of 4-bromomethyl-7-methoxycoumarin to a 10-mL volumetric flask, dissolve in and dilute with acetone to volume, and mix. Store this solution in a dark place.
Test solution— Transfer 10.0 g of finely powdered Saw Palmetto to a 250-mL round-bottom flask fitted with a reflux condenser. Add 150 mL of alcohol, and heat under a reflux condenser on a steam bath for 1 hour. Cool, filter, wash the residue with alcohol, and dilute the combined washings and filtrate with alcohol to 200.0 mL. Transfer 0.6 mL of this solution to a suitable flask, and evaporate to dryness. To the residue add 1.0 mL of the Reagent solution, and mix. Transfer this solution with the aid of a pipet to an amber glass vial fitted with a metal-clamped rubber cap. Add 3 µL of tris-[2-(2-methoxyethoxy)ethyl]amine and 10 mg of lithium carbonate to the vial, replace the metal-clamped rubber cap, and dry at 105 for 2 hours. Cool, and use the cooled solution as the test solution.
Standard solution— Transfer 5.0 g of magnesium stearate to a 100-mL round-bottom flask fitted with a reflux condenser. Add 50 mL of ether, 20 mL of 12.5% nitric acid, and 20 mL of water, and heat until solution is complete. Cool, transfer the contents of the flask to a separatory funnel, and withdraw the lower aqueous phase. Extract the ether phase twice, each time using 4 mL of water, separating the aqueous phases. Extract the combined aqueous phases with 15 mL of ether, combining the ether extracts. Evaporate to dryness, and dry the residue at 105. Transfer 1 mg of the residue to an amber glass vial fitted with a metal-clamped rubber cap. Add 10 mg of lithium carbonate, 3 µL of tris-[2-(2-methoxyethoxy)ethyl]amine, and 1.0 mg of the Reagent solution, replace the metal-clamped rubber cap, dry at 105 for 2 hours, and cool.
Blank solution— To 10 mg of lithium carbonate in an amber glass vial fitted with a metal-clamped rubber cap, add 3 µL of tris-[2-(2-methoxyethoxy)ethyl]amine and 1.0 mL of the Reagent solution, replace the metal-clamped rubber cap, dry at 105 for 2 hours, and cool.
Procedure— Separately apply 2 µL each of the Test solution, the Standard solution, and the Blank solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture, and allow the spots to dry. Develop the chromatograms in a solvent system consisting of a mixture of cyclohexane, ethyl acetate, and acetic acid (70:30:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chromatographic chamber, mark the solvent front, and allow the plate to air-dry. Examine the plate under long-wavelength UV light. The chromatogram of the Test solution exhibits at least two zones of blue fluorescence corresponding in RF values to similar zones exhibited in the chromatogram of the Standard solution. The blue fluorescent zones from the Test solution appear above the blue fluorescent zones exhibited in the chromatogram of the Blank solution.
Foreign organic matter 561: not more than 2.0%.
Loss on drying 731 Dry 1.0 g of finely powdered Saw Palmetto at 105 for 2 hours: it loses not more than 12.0% of its weight.
Total ash 561: not more than 5.0%, determined on 1.0 g of finely powdered Saw Palmetto.
Acid-insoluble ash 561: not more than 1.0%.
Heavy metals 231: not more than 0.001%.
Volatile oil content 561: not less than 2 mL per 100 g of fruits of an oil that solidifies to a white solid at room temperature is obtained.
Pesticide residues 561: meets the requirements.
Microbial enumeration 2021 The total bacterial count does not exceed 104 cfu per g, the total combined molds and yeasts count does not exceed 100 cfu per g, and it meets the requirements of the test for absence of Salmonella species and Escherichia coli and for absence of Staphylococcus aureus.
Content of lipophilic extract— Pulverize about 100 g of Saw Palmetto, and transfer 10 g, accurately weighed, to a 250-mL round-bottom flask fitted with a reflux condenser, add 150 mL of alcohol, and mix. Heat the flask on a boiling water bath under reflux for 1 hour. Cool, filter, and wash the residue with small portions of alcohol. Collect the filtrate and washings in a 200-mL volumetric flask, dilute with alcohol to volume, and mix. Evaporate 100.0 mL of this solution to dryness in a rotary evaporator under vacuum. Add 40 mL of n-hexane to the residue, stir for 5 minutes, filter, and collect the filtrate in a round-bottom flask. Repeat the above operation of washing with n-hexane two more times, and collect all of the filtrates in the same flask. Using a rotary evaporator, evaporate off the organic solvent to dryness. Dry the residue obtained at 105 for 2 hours: the weight of the residue is not less than 0.35 g (7%).
Content of fatty acids—
Internal standard solution— Dissolve an accurately weighed quantity of nonadecane in hexanes to obtain a solution having a known concentration of about 12 mg per mL.
Standard solution— Dissolve accurately weighed quantities of USP Methyl Laurate RS, USP Methyl Oleate RS, USP Methyl Myristate RS, USP Methyl Palmitate RS, USP Methyl Linoleate RS, USP Methyl Caproate RS, USP Methyl Caprylate RS, USP Methyl Caprate RS, USP Methyl Palmitoleate RS, USP Methyl Stearate RS, and USP Methyl Linolenate RS in hexanes to obtain a solution having a known concentration of each methyl ester as given below. Transfer 1.0 mL of Internal standard solution to 5.0 mL of this solution, and mix.
Methyl ester Concentration (in mg per mL)
Methyl laurate 5
Methyl oleate 5
Methyl myristate 2
Methyl palmitate 2
Methyl linoleate 1
Methyl caproate 0.4
Methyl caprylate 0.4
Methyl caprate 0.4
Methyl palmitoleate 0.4
Methyl stearate 0.4
Methyl linolenate 0.4
Test solution— Pulverize about 50 g of dried Saw Palmetto to a moderately coarse powder. Transfer an accurately weighed quantity of about 1 g of the pulverized powder to a 100-mL round-bottom flask fitted with a water-cooled reflux condenser and a magnetic bar. Add 10 mL of 0.5 N methanolic sodium hydroxide solution (prepared by dissolving 0.2 g of sodium hydroxide in 10 mL of methanol), and heat the flask with stirring under reflux conditions for 15 minutes. Pipet 5 mL of a solution of boron trifluoride in methanol (prepared by dissolving 1.4 g of boron trifluoride in 10 mL of methanol) through the reflux condenser into the flask, and continue boiling for 2 more minutes. Add 5.0 mL of hexanes through the condenser, and continue boiling for an additional 1 minute. Cool the flask, remove the condenser, add about 15 mL of saturated sodium chloride solution, and add 1.0 mL of the Internal standard solution. While the solution is still tepid, insert a stopper into the flask, and shake vigorously. Pipet 1.0 mL of the upper hexanes layer into a glass-stoppered test tube containing a small quantity of anhydrous sodium sulfate. Filter the solution, and, if necessary, dilute an accurately measured volume of the filtrate with hexanes to obtain a known volume. Store this solution in a refrigerator until just prior to use.
Chromatographic system (see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector maintained at 300 and a 0.25-mm × 30-m fused silica capillary column coated with a 0.25-µm film of phase G16. The injection port is maintained at 250. The column temperature is initially held at 120 for 3 minutes, then programmed to rise to 220 at the rate of 50 per minute, where it is maintained for an additional 12 minutes. The carrier gas is helium flowing at a rate of about 1 mL per minute. Chromatograph the Standard solution, and record the responses as directed for Procedure: the relative retention times are about 0.39 for methyl caproate, 0.56 for methyl caprylate, 0.76 for methyl caprate, 0.94 for methyl laurate, 1.0 for nonadecane (internal standard), 1.1 for methyl myristate, 1.3 for methyl palmitate, 1.35 for methyl palmitoleate, 1.65 for methyl stearate, 1.7 for methyl oleate, 1.8 for methyl linoleate, and 2.0 for methyl linolenate; the resolution, R, between the methyl stearate and methyl oleate peaks is not less than 1.5; the tailing factor for each of the methyl ester peaks in the Standard solution is not greater than 2.0, and the relative standard deviation for replicate injections for each of the methyl ester peaks is not more than 5.0%.
Procedure— Separately inject equal volumes (about 1 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses of the fatty acid esters. Calculate the percentage of each fatty acid in the portion of the Saw Palmetto taken by the formula:
500(C / W)(RU / RS)( MA / ME)
in which C is the concentration, in mg per mL, of the respective methyl ester in the Standard solution, W is the weight, in mg, of pulverized Saw Palmetto taken to prepare the Test solution, RU and RS are the ratios of the responses of the relevant methyl ester peak and the internal standard peak obtained from the Test solution and the Standard solution, respectively, and MA and ME are the molecular weights of the relevant fatty acid and its methyl ester, respectively: the percentages of individual fatty acids obtained are not less than 3.0% of oleic and 2.0% of lauric acid, 1.2% of myristic acid, 1.0% of palmitic acid, 0.4% of linoleic acid, 0.2% each of caproic acid, caprylic acid, and capric acid, 0.1% of stearic acid, 0.5% of linolenic acid, and 0.01% of palmitoleic acid. The sum of the percentages of all the fatty acids is not less than 9.0%.
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Topic/Question Contact Expert Committee
Monograph Maged H. Sharaf, Ph.D.
Senior Scientist
(DSB05) Dietary Supplements - Botanicals
Reference Standards Lili Wang, Technical Services Scientist
2021 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(MSA05) Microbiology and Sterility Assurance
USP32–NF27 Page 1069
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.