Myricaceae

A small family — three or four genera — of aromatic shrubs that grow where little else will: acid bog, heath, sand dune and poor coastal soil. They manage it by fixing atmospheric nitrogen through root nodules containing Frankia actinobacteria, an ability otherwise associated with legumes. Almost every part is dotted with yellow resinous glands, and those glands are the family’s pharmacy.

The family has two distinct reputations, and only one is a systemic medicine.

Bayberry root bark (Myrica cerifera) is the older Western herbal entry — a strong astringent of the Physiomedicalist tradition, used for diarrhoea, relaxed mucous membranes and as a gargle. Its reputation rests on tannin content and on triterpenes including myricadiol.

Sweet gale — bog myrtle (Myrica gale) — is the family’s better-documented plant, and its case is external rather than internal. The leaf oil is a genuine insect repellent, tested in human arm-in-cage studies against midges and mosquitoes, and used commercially in Scotland on that basis. Sweet gale was also the principal bittering and preserving herb of gruit ale across northern Europe before hops displaced it — a documented six-century brewing history rather than a folk claim.

Alongside these sits Chinese bayberry (M. rubra, yangmei), an important East Asian fruit crop whose anthocyanin-rich drupes have their own metabolic and antioxidant literature. The three are routinely conflated in secondary sources and should not be.

• C-methylated dihydrochalcones — myrigalone A, myrigalone B and angoletin, a distinctive and unusually narrow chemical group in the fruit exudate of sweet gale. Near-identical structures differing in a single hydrogen bond behave completely differently: one is a potent antioxidant, one an allelochemical, one essentially inert.
• Diarylheptanoids — galeon and its relatives, macrocyclic phenolics quite separate from the chalcones despite frequently being filed with them.
• Essential oil — α-pinene, 1,8-cineole, limonene, β-caryophyllene and germacrone; the repellent activity tracks the whole oil rather than any single constituent.
• Tannins and triterpenes — the astringency of bayberry root bark, plus myricadiol and taraxerol.
• Flavonols — myricetin is named for this genus and occurs throughout it.