Шавлія

The plant

Salvia officinalis is a perennial, evergreen subshrub with woody stems, grayish leaves, and blue to purplish flowers. It is native to the Mediterranean region and has been naturalized in many places throughout the world. Carl Linnaeus described it in 1753. It is the type species of the genus Salvia. The Old World type grows to about 60 cm tall and wide and flowers in late spring or summer. The oblong leaves are up to 65 mm long and 25 mm wide; they are grey-green and rugose above and nearly white beneath because of many short soft hairs.

Composition

Three sage leaf oils were dominated by the monoterpenoids α-thujone, 1,8-cineole and camphor, a profile similar to many reported oils and notably different from many others. In three analysed leaf oils, α-thujone made up 17.2–27.4%, 1,8-cineole 11.9–26.9% and camphor 12.8–21.4%. Lesser amounts of β-thujone (3.8–6.0%), camphene (3.5–5.3%) and α-humulene (3.1–4.4%) were present. Commercial sage oil is generally characterized by thujones, with α-thujone usually predominating over β-thujone. Sage oils can vary widely in their chemical compositions. A cluster analysis of 185 reported oil compositions revealed five major chemotypes. The most common chemotype has α-thujone above camphor above 1,8-cineole. The other four are an α-humulene-rich chemotype, a β-thujone-rich chemotype, a 1,8-cineole/camphor chemotype and a sclareol/α-thujone chemotype. Among 25 indigenous populations growing in the Dalmatian region of Croatia, three chemotypes have been delineated. A leaf oil from Abha, Saudi Arabia, had camphor (20.3%), 1,8-cineole (15.0%), α-thujone (14.9%) and viridiflorol (9.9%) as major compounds. For medicinal use, ISO 9909 sets these ranges: cis-thujone 18–43%, camphor 4.5–24.5% and cineole 5.5–13%. Yield and composition depend on genetic background, region, environmental conditions, season, the plant parts used and the extraction method.

Culinary use

In Italian cooking, sage is an essential ingredient of saltimbocca and other dishes, and it is also fried to make salvia fritta.

Thujone

Thujone is a ketone and a monoterpene that occurs predominantly in two diastereomeric forms, α-thujone and β-thujone. More than 20% of sage oil comes from alpha and beta thujones. Thujone is a GABA-A receptor antagonist; by inhibiting GABA receptor activation it may let neurons fire more easily, which can cause muscle spasms and convulsions. In mice, the median lethal dose of α-thujone, the more active of the two isomers, is around 45 mg/kg. High doses of α-thujone cause convulsions by blocking GABA-gated chloride channels. Thujone is a neurotoxin that can cause convulsions in animals and severe intoxication in humans, and a daily limit of 6 mg is recommended for supplemental use. α-Thujone was once thought to be the hallucinogenic constituent of absinthe and the cause of absinthism, which has been shown to be false.