Lemon leaves are not the leaves of the lemon tree, but the leaves of the Rutaceae plant Lemon or lemon, which can be harvested throughout the year. It has the effect of dissolving phlegm and relieving cough, regulating qi and opening the stomach, and treating cough and wheezing, bloating, diarrhea and other diseases.

Lemon leaves contain flavonoids, coumarins, organic acids and so on. Among the flavonoids, there are quercetin and rhizopodophyllin. Among the coumarins, there are umbelliferolide, scopolamine and horse chestnut barkin. Among the organic acids, there are ferulic acid, p-coumaric acid, salicylic acid, p-hydroxyphenylacetic acid, erucic acid, p-hydroxybenzoic acid, vanillic acid, gentianic acid and o-coumaric acid; it also contains vanillin aldehyde. Each of the above components, mainly in bound form, of which umbelliferolide, ferulic acid and salicylic acid at the same time in small amounts of free form. The leaves also contain volatile oil, vitamin C-119-232 mg% and pigments such as chlorophyll a, chlorophyll b, lutein, butterfly plum flavin.