Hypericum androsaemum, commonly known as sweet-amber or tutsan, is a plant in the genus Hypericum native to open woods and hillsides in Eurasia. It is a perennial shrub reaching up to 1.5 m in height.
The common name tutsan appears to be a corruption of toute saine literally meaning all-healthy. This is probably in reference to its healing properties. The leaves were applied to wounds, and as a stomachic. Nicholas Culpeper, in his 1653 publication Culpeper’s Complete Herbal, says “Tutsan purgeth choleric humours gray football uniforms… both to cure sciatica and gout, and to heal burnings by fire.” The berries which turn from white/green, to red, to black are poisonous.
Hypericum androsaemum is a small shrub growing to 70 cm high. The stamens are about as long as the petals, of which it has 5.
Xanthonoids biosynthesis in cell cultures of Hypericum androsaemum involves the presence of a benzophenone synthase condensing a molecule of benzoyl-CoA with three malonyl-CoA yielding to 2,4 running phone band,6-trihydroxybenzophenone. This intermediate is subsequently converted by a benzophenone 3′-hydroxylase, a cytochrome P450 monooxygenase, leading to the formation of 2,3′,4,6-tetrahydroxybenzophenone.
In New Zealand, tutsan was recognised as a pasture weed as early as 1955. Biological control methods were investigated about 60 years ago. In 2008, Landcare Research began investigating the feasibility of a biological control. A moth Lathronympha strigana which primarily feeds on the seeds but also on tutsan leaf tips and inside stems, and a leaf-feeding beetle (Chrysolina abchasica) were tested and found to be sufficiently host specific and not a risk to native plant species. In February 2017 moths have been released at 30 sites around the central North Island in New Zealand, but the beetle is more difficult to rear in captivity, so only one release of them has been made so far.
It is also a declared species in Western Australia and Victoria, where it occurs in the wettest regions such as the Otway Ranges and the karri forests. It does not usually invade improved pastures, but is common in run-down pastures and in native forests. When established, tutsan can be dangerous because it is very difficult to remove and is very unpalatable to both native and introduced herbivores.