สารบัญ

Thai name เปลือกมะนาวฝรั่งแห้ง (PLUEAK MA-NAO FA-RANG HAENG)

Category  Pharmaceutic aid.

        Dried Lemon Peel is the dried outer part of the pericarp of the ripe, or nearly ripe, fruit of Citrus ´ limon (L.) Osbeck (Family Rutaceae).  It yields not less than 2.0 mL of lemon oil from each 100 g of drug.

Constituents  Dried Lemon Peel contains flavonoids and their glycosides such as naringin, neohesperidin, hesperidin, and rutin.  Others are coumarins, monosaccharides, phenolic acids namely caffeic acid, etc.

Description  Odour aromatic, characteristic; taste aromatic and bitter.
Macroscopical  Strips or pieces with a marked thickening of the epicarp around the calyx; externally yellow and somewhat rough from the presence of numerous minute pits, each corresponding to an oil gland; internally with a small remnant of white spongy pericarp.  Fracture short.
Macroscopical  Transverse section of the dried peel shows epidermis, parenchyma, vascular bundle, and prismatic crystal of calcium oxalate.  Epidermis:  small thin-walled cells with underlying parenchyma containing numerous large oil glands and scattered small strands of vascular tissue.  Prismatic crystals of calcium oxalate occurring throughout the parenchyma, particular abundant in the layers adjacent to the epidermis.

Packaging and storage  Dried Lemon Peel shall be kept in tightly closed containers, at a temperature not exceeding 25°.

Identification  Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1).
     Standard solution  Prepare a solution containing 0.01 per cent w/v each of caffeic acid and naringin, and 0.025 per cent w/v of rutin, in methanol.
     Test solution  Add 1 g of freshly cut peel to 10 mL of methanol and heat in a water-bath at 65° for 5 minutes, shaking frequently.  Allow to cool and filter.
     Adsorbent  Silica gel G.
     Mobile phase  Water, anhydrous formic acid, 2-butanone, ethyl acetate (10:10:30:50).
     Application  Apply 20 µL of Standard solution and Test solution as 10-mm bands.
     Development and drying  Dry the developed plate at 105°.
     Detection  Spray the warm plate with a 1 per cent w/v solution of diphenylboric acid aminoethyl ester in methanol, then with a 5 per cent w/v solution of polyethylene glycol 400 in methanol, allow the plate to dry in air for about 30 minutes and examine under ultraviolet light (366 nm). Observe the result.
     Results  When examined under ultraviolet light
(366 nm), the test solution shows a yellowish brown fluorescent band due to rutin and above it, an intense red fluorescent band and further above, a very weak greenish fluorescent band due to naringin in the chromatogram, corresponding in colour and R_f to the bands shown by the standard solution.  Other coloured bands are also shown in the chromatogram.

Assay  Carry out the method for the “Determination of Volatile Oil” (Appendix 7.3), using 20 g, accurately weighed and crushed under water.  Use 300 mL of water as the distillation liquid and a 500-mL round-bottomed flask.  Distil at a rate of 2 to 3 mL per minute for 3 hours.  Use 0.2 ml of xylene in the graduated tube.