Powdered Forskohlii
DEFINITION
Powdered Forskohlii is Forskohlii reduced to a powder or very fine powder. It contains NLT 0.4% of forskolin, calculated on the dried basis.
IDENTIFICATION
• A. Thin-Layer Chromatographic Identification Test 
201
201
Standard solution A:
50 µg/mL of USP Forskolin RS in acetonitrile. Sonicate for about 10 min.
Standard solution B:
5 mg/mL of USP Powdered Forskohlii Extract RS in acetonitrile. Sonicate for about 15 min, centrifuge, and use the supernatant.
Sample stock solution:
Use the Sample solution, prepared as directed in the test for Content of Forskolin.
Sample solution:
Dilute 10 mL of the Sample stock solution with acetonitrile to 25 mL.
Adsorbent:
Chromatographic silica gel with an average particle size of 10–15 µm (TLC plates)
Application volume:
10 µL, as 4-mm bands
Developing solvent system:
A mixture of toluene and ethyl acetate (85:15)
Spray reagent:
A mixture of 5% vanillin in glacial acetic acid and 10% sulfuric acid in water (1:1)
Analysis
Samples:
Standard solution A, Standard solution B, and Sample solution
Apply the samples as bands to a suitable thin-layer chromatographic plate (see Chromatography 621). Use saturated chamber. Develop the chromatograms until the solvent front has moved up about 90% of the plate. Remove the plate from the chamber, dry, spray with the Spray reagent, heat for 5–10 min at 105
, and examine under visible light.
621). Use saturated chamber. Develop the chromatograms until the solvent front has moved up about 90% of the plate. Remove the plate from the chamber, dry, spray with the Spray reagent, heat for 5–10 min at 105, and examine under visible light.
Acceptance criteria:
The Sample solution exhibits a violet zone due to forskolin at an RF value of approximately 0.3, corresponding in color and RF to that from Standard solution A; and a minor violet zone, a pink zone, and a brick red zone at RF values of approximately 0.1, 0.62, and 0.69, due to isoforskolin, 1,9-dideoxyforskolin, and crocetindialdehyde, respectively. Zones detected from the Sample solution correspond in position and color to zones from Standard solution B. Other minor zones may be observed from the Sample solution and Standard solution B.
• B.
The Sample solution from the test for Content of Forskolin shows a main peak at a retention time corresponding to that of forskolin from Standard solution A. Identify other diterpene peaks in the Sample solution by comparison with Standard solution B and the reference chromatogram provided with the lot of USP Powdered Forskohlii Extract RS being used. The Sample solution shows an additional peak corresponding to isoforskolin.
COMPOSITION
• Content of Forskolin
Solution A:
Use filtered and degassed acetonitrile.
Solution B:
Use filtered and degassed water.
Standard solution A:
Sonicate a quantity of USP Forskolin RS in acetonitrile to obtain a solution having a known concentration of about 1.0 mg/mL.
Standard solution B:
5 mg/mL of USP Powdered Forskohlii Extract RS in acetonitrile. Sonicate for about 15 min, centrifuge, and use the supernatant. Before injection, pass through a membrane filter having a 0.45-µm or finer pore size.
Sample solution:
Transfer about 3.0 g of Powdered Forskohlii to a 100-mL round-bottom flask fitted with a reflux condenser. Add 50 mL of acetonitrile, reflux on a water bath for 20 min, cool to room temperature, and decant the supernatant. Repeat until the last extract is colorless. Combine the extracts, filter, concentrate under vacuum, and adjust the volume with acetonitrile to 100 mL. Before injection, pass through a membrane filter having a 0.45-µm or finer pore size, discarding the first 5 mL of the filtrate.
System suitability solution:
A mixture of Standard solution A and 0.01% toluene in acetonitrile (1:1)
Mobile phase:
See the gradient table below.
| Time (min) |
Solution A (%) |
Solution B (%) |
|---|---|---|
| 0 | 45 | 55 |
| 25 | 45 | 55 |
| 28 | 95 | 5 |
| 35 | 95 | 5 |
| 36 | 45 | 55 |
| 45 | 45 | 55 |
Chromatographic system
Mode:
LC
Detector:
UV 220 nm
Column:
4.6-mm × 25-cm; 5-µm, 100 
Column temperature:
30 ± 2
Flow rate:
1.8 mL/min
Injection size:
20 µL
System suitability
Samples:
Standard solution A, Standard solution B, and System suitability solution
[Note—The relative retention times for isoforskolin and forskolin are 0.51 and 1.00, respectively. ]
Suitability requirements:
The chromatogram from Standard solution B is similar to the reference chromatogram provided with the lot of USP Powdered Forskohlii Extract RS being used.
Relative standard deviation:
NMT 2% determined from the forskolin peak in repeated injections, Standard solution A
Resolution:
NLT 1.5 between the forskolin and toluene peaks, System suitability solution
Analysis
Samples:
Standard solution A, Standard solution B, and Sample solution
Using the chromatogram of Standard solution A, Standard solution B, and the reference chromatogram provided with the lot of USP Powdered Forskohlii Extract RS being used, identify the retention times of the peaks corresponding to isoforskolin and forskolin.
Calculate the percentage of forskolin in the portion of Powdered Forskohlii taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = peak response of forskolin from the Sample solution |
| rS | = | = peak response of forskolin from Standard solution A |
| CS | = | = concentration of USP Forskolin RS in Standard solution A (mg/mL) |
| CU | = | = concentration of Powdered Forskohlii in the Sample solution (mg/mL) |
Acceptance criteria:
NLT 0.4% is found on the dried basis.
IMPURITIES
Inorganic Impurities
• Heavy Metals, Method III 231:
NMT 20 ppm
231:
NMT 20 ppm
Organic Impurities
• Procedure: Articles of Botanical Origin, General Method for Pesticide Residues Analysis 561:
Meets the requirements
561:
Meets the requirements
SPECIFIC TESTS
• Botanic Characteristics:
Yellowish brown powder; characteristic and pleasant aromatic odor; and slightly bitter to pungent taste. Under a microscope, it shows the presence of parenchyma cells with oleoresin canals, starch grains and prisms of calcium oxalate; oil globules; simple starch grains, cork cells; sclereids; stone cells; pitted vessels; and thin-wall fibers.
• Loss on Drying 731:
Dry 1.0 g of Powdered Forskohlii at 105 for 3 h: it loses NMT 12.0% of its weight.
731:
Dry 1.0 g of Powdered Forskohlii at 105 for 3 h: it loses NMT 12.0% of its weight.
• Articles of Botanical Origin, Total Ash 561:
NMT 6%, determined on 1.0 g of Powdered Forskohlii
561:
NMT 6%, determined on 1.0 g of Powdered Forskohlii
• Microbial Enumeration Tests 2021:
The total aerobic bacterial count does not exceed 105 cfu/g; the total combined molds and yeasts count does not exceed 103 cfu/g; and the bile-tolerant Gram-negative bacteria does not exceed 103 cfu/g.
2021:
The total aerobic bacterial count does not exceed 105 cfu/g; the total combined molds and yeasts count does not exceed 103 cfu/g; and the bile-tolerant Gram-negative bacteria does not exceed 103 cfu/g.
• Microbiological Procedures for Absence of Specified Microorganisms 2022:
Meets the requirements of the tests for absence of Salmonella species and Escherichia coli
2022:
Meets the requirements of the tests for absence of Salmonella species and Escherichia coli
• Articles of Botanical Origin, Test for Aflatoxins 561:
Meets the requirements
561:
Meets the requirements
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers, protected from light and moisture, and store at room temperature.
• Labeling:
The label states the Latin binomial and, following the official name, the parts of the plant contained in the article.
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Maged H. Sharaf, Ph.D.
Principal Scientific Liaison 1-301-816-8318 |
(DS2010) Monographs - Dietary Supplements |
| 2021 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
| 2022 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 1300
Pharmacopeial Forum: Volume No. 36(3) Page 697