Lemon balm is a rich source of antioxidant phenolic compounds,[1][2] but its leaves have a relatively low essential oil content for a plant in the mint family, ranging from 0.01 to 0.72% of dry weight,[3] with a tea extracting 10 mg/L.[4] Because of the herb’s low content of volatile essential oil, the herb may be best used within six months of harvest.[5]
Leaves: The dried leaves contain many polyphenols, notably rosmarinic acid, caffeic acid, chlorogenic acid, ferulic acid, isoquercetin (a glucoside of quercetin), gallic acid, and rutin; they also contain several triterpenes, notably oleanolic acid and ursolic acid.[3] Lemon balm extracts use different solvents and different methods of extraction, which results in widely varying compositions.
Essential oil: There are two subspecies of lemon balm, M. officinalis officinalis and M. officinalis altissima, which differ in the composition of their essential oils: The oil of the officinalis subspecies contains important amounts of citral and/or neral, whereas these are only present in small quantities in the oil of the altissima subspecies. The composition of the essential oil also varies depending on where the plant is grown and the season in which the leaves are harvested. That said, the principal constituents of M. officinalis essential oil are as follows:[3]
| Constituent | Concentration (%) |
|---|---|
| Geranial (citral A) | 6.22–51.21 |
| Neral (citral B) | 4.28–35.02 |
| Caryophyllene oxide | 1.3–43.55 |
| β-Caryophyllene | 1.3–29.14 |
| Citronellal | 0.4–20.3 |
| Geranyl acetate | 0.5–19.3 |
| (E)-Caryophyllene | 1.06–6.8 |
| α-Copaene | 0.1–7.02 |
| α-Cadinol | 5.64 |
Taken from: Petrisor G et al. Melissa officinalis: Composition, Pharmacological Effects and Derived Release Systems – A Review. Int J Mol Sci. 2022 Mar 25;23(7):3591. doi:10.3390/ijms23073591.