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Category  Carminative.

        Peppermint Leaf consists of the dried leaf of Mentha × piperita L. (Family Lamiaceae).  It yields not less than 1.2 mL of volatile oil from each 100 g of drug, calculated on the anhydrous basis.

Origin of plant Peppermint is native to Europe and Middle East and is commercially cultivated in eastern and northern Europe and the United States of America.  It is also found in Africa.

Constituents  The major constituent of Peppermint Leaf is a volatile oil containing predominantly menthol and menthone.  It also contains flavonoids (e.g., luteolin and rutin), phenolic acids, including rosmarinic acid, and a small amount of triterpenes.

Description  Odour, aromatic, penetrating, menthol-like; taste, aromatic, characteristic.
Macroscopical  Entire, cut, or broken leaves, thin, fragile, and usually crumpled, green to brownish green, and in some varieties, with brownish purple veins.  Entire leaf ovate or lanceolate, 3 to 9 cm long, 1 to 3 cm wide, apex acuminate, base uneven, margin shapely dentate, venation prominently pinnate on the lower surface, with lateral veins leaving the midrib at about 45^º.  Petiole green or brownish violet, grooved, typically 0.5 to 1 cm long, up to 1 mm in diameter.
Microscopical  Powdered drug of Peppermint Leaf shows adaxial epidermis, abaxial epidermis, covering trichomes, glandular trichomes, fragments from near the leaf margin, fragments of dorsiventral mesophyll, and crystals of menthol.  Adaxial epidermis:  sinuous-wavy walled cells with cuticle striated over the veins associated with palisade parenchyma.  Abaxial epidermis with diacytic stomata.  Covering trichome: 
3 to 8 elongated cells, uniseriate and with striated cuticle.  Glandular trichomes of 2 types:  1) unicellular stalk with small rounded unicellular head and 2) unicellular stalk with enlarged oval head consisting of 8 radiating cells.  Fragments from near the leaf margin:  isodiametric cells with beaded and more or less straight anticlinal walls; covering trichomes, unicellular or bicellular, short, conical.  Fragments of dorsiventral mesophyll:  a layer of palisade cells and 4 to 6 layers of spongy parenchyma.  Crystals of menthol yellowish, present under the cuticle of secretory cells.

Other relevant information  Peppermint leaf should not be used in patients with gallstones unless under medical supervision.

Packaging and storage  Peppermint Leaf shall be kept in well-closed containers, protected from light.

Identification  Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1).
Standard solution  Dissolve 2 mg of luteolin-7-glucoside, 2 mg of rutoside trihydrate, and 5 mg of rosmarinic acid in 10 mL of methanol.
Test solution  To 0.5 g, in No. 355 powder, add 2.5 mL of methanol and 2.5 mL of water, sonicate for 5 minutes, and filter.
Adsorbent  Silica gel F254.
Mobile phase  Acetic acid, anhydrous formic acid, water, and ethyl acetate (7:7:18:68).
Application  Apply 4 µL each of Standard solution and Test solution as 8-mm bands.
Development and drying  Allow the solvent front to ascend 6 cm above the line of application.  Dry the developed plate in air.
Detection  Heat at 105° for 5 minutes, spray the warm plate with a 1 per cent w/v of diphenylboric acid aminoethyl ester in methanol, and then with a 5 per cent w/v of macrogol 400 in methanol.  Alternatively, dip the warm plate in a 0.5 per cent w/v of diphenylboric acid aminoethyl ester in ethyl acetate, then in a 5 per cent w/v of macrogol 400 in dichloromethane.  Allow to dry in air for about 1 minute and examine the plate under ultraviolet light (366 nm).
Results  When examined under ultraviolet light (366 nm), the test solution shows a light blue fluorescent band due to rosmarinic acid in the upper third of the chromatogram, corresponding in colour and R_f to the band shown by the standard solution.  Two orange-yellow fluorescent bands, a red fluorescent band in the middle of the chromatogram and an orange-yellow fluorescent band in the lower third of the chromatogram are present. 
Two orange fluorescent bands of luteolin-7-glucoside and rutoside obtained from the standard solution appear around the middle of the chromatogram.

Foreign matter  Not more than 5 per cent of stem; diameter of the stems, not greater than 1.5 mm; not more than 2 per cent of foreign elements; not more than 8 per cent of leaf showing brown stains due to Puccinia menthae (Appendix 7.2);  use 10 g.

Total ash  Not more than 15.0 per cent w/w (Appendix 7.7).

Acid-insoluble ash  Not more than 1.5 per cent w/w (Appendix 7.6).

Water  Not more than 11.0 per cent v/w (Azeotropic Distillation Method, Appendix 4.12); use 20 g.

Assay  Carry out the method for the “Determination of Volatile Oil” (Appendix 7.3), using 20 g, accurately weighed.  Use 200 mL of water as the distillation liquid and a 500-mL round-bottomed flask.  Distill at a rate of 2 to 4 mL per minute for 2 hours.  Using 0.5 mL of xylene in the graduated tube.