fresh leaves contain .8~1% of volatile oil, and dry stems and leaves contain 1.3~2%. The main component in the oil is Menthol, the content of which is about 77-78%, followed by Menthone, the content of which is 8-12%, and it also contains Menthyl acetate, Camphene, Limonene, IsoMenthenone and isomenthone. Fresh stems and leaves contain about 1% volatile oil, and dry stems and leaves contain 1.3%-2% oil. The oil mainly contains about 77%-87% l-menthol, followed by about 1% l-menthone. In addition, it contains isomenthone, pulegone, decylacetate, menthyl acetate, menthyl benzoate, α-pinene, pentanol -3, β-pinene, β-thu. In addition, leaves still contain many free amino acids such as threonine, alanine, glutamic acid and asparagine. It is said to contain resin and a small amount of tannin and rosmarinic acid. There are also a variety of flavonoids.

Chemical identification:

(1) Take a little leaf powder of this product, and sublimate it slightly to get an oil. Quickly add 2 drops of sulfuric acid and a little vanillin crystals to make it yellow to orange, and then add 1 drop of water to make it purple. (menthol)

(2) Take .5g of this product, add 5ml of petroleum ether (6-9℃), seal it, shake it for a few minutes, leave it for 3min, filter the filtrate for sampling, and prepare a reference solution containing 2mg per ml with menthol as the reference. Spot samples on silica gel G thin-layer plate respectively, spread with benzene-ethyl acetate (19:1) as developing agent, take them out and dry them, spray 2% vanillin sulfuric acid test solution, and heat them at 98℃ for 2-5 minutes. In the chromatogram of the test sample, rose red spots appear at the positions corresponding to the chromatogram of the control sample.