Not to be semantically confused with the Genera : Cotula [which means 'cup' in Greek, and names the Buttonweeds group, which also belong to the same Daisy & Dandelion Family as does Anthemis cotula] nor with Chameleon (Houttuynia cordata) which belongs to the Chameleon Family (Saururaceae).
Easily mis-identified visually as :
But is easily distinguished from another 'Mayweed' Pineapple Weed (Matricaria discoides) which lacks ray florets (petals), possesses just a central yellow dome of yellow disc-florets, and smells of pineapples when crushed
- other so-called 'Chamomiles' such as
Chamomile (Chamomile mixtum) itself (which is scented and strongly aromatic)
- Corn Chamomile (Anthemis arvensis) (which is scarcely scented)
Sicilian Chamomile (Anthemis punctata) (which grows mainly near the sea)
Austrian Chamomile (Anthemis austriaca) (which has neater more-regularly branched leaflets)
Yellow Chamomile (Anthemis arvensis) (but that has yellow 'ligules' - minute flaps at base of the leaves)
- and other so-called 'Mayweeds' such as
Scented Mayweed (Matricaria chamomilla) which is strongly sweetly scented when fresh.
- Sea Mayweed (Tripleurospermum maritima) but that is shoter and more succulent and grows on shingle/sand beside the sea.
Scentless Mayweed (Tripleurospermum maritimun ssp. inodorum) which, although a sub-species of Sea Mayweed, is not succulent and lacks any smell when crushed.
However, Stinking Mayweed stinks, and thus is easily recognisable from all the above by means of this unique feature (for Mayweeds/Chamomiles) alone! Both Stinking Chamomile and
Scentless Mayweed (Tripleurospermum maritimun ssp. inodorum) are much the more likely species to be seen in early Autumn.
Uniquely identifiable characteristics (for Mayweeds/Chamomiles)
Distinguishing Feature : it smells sickly/nauseous when crushed (rather than sweetly or aromatically).
It lacks a pappus ('seed-clock').
The plant smells nauseous when crushed, one of the most reliable identifying features. Stinking Chamomile is mildly toxic to livestock (and presumably humans too), not least because of the presence of polyacetylenes and sesquiterpene lactones. The aerial parts also contain two flavones, Apigenin and Hispidulin
It also contains several poisonous
polyacetylenes (polyynes) all based upon DeHydroMatricaria Ester, which contains not just 2 triple bonds as Matricaria Ester, but three (hence the '8-dehydro' prefix). There are also three (only two of which are shown) methyl-thio derivatives of this, containing only 2 triple bonds. The shape of the molecules is shown only schematically, the Z- and E- bends are not depicted.
These polyynes occur in the roots of the plant and exhibit significant anti-mycobacterial action as well as allergenic activity.
The plant contains
Anthecotulide, a non-volatile oil, is a
sesquiterpene lactone known to be a potent contact allergen. It is present in the leaves at 1.5% and in the flowers at 7%. There are five more sequiterpene lactones present with similar, but not identical, side-chains. The extra side-chains are variously -OH groups or -O-CH3 groups. (Claims that this potent allergen is sometimes found in the essential oils nominally obtained from Chamomile is highly likely to be due to contamination of Chamomile collections with Stinking Mayweed; they look very similar in the field).
The 5,6-epoxide of Anthecotulide is also present, and one assumes it is more potent that Anthecotulide itself.
An ACETOPHENONE and a related CHROMANOME
These compounds are common in members of the Dandelion & Daisy family and are present in the aerial parts of Anthemis species, which includes Stinking chamomile.
Benzopyrones (chromenes) like both the above exhibit growth-inhibitory and anti-inflammatory activity in yellow mealworm larvae. Prenylated Acetophenones may also have phytoalexin activity; anti-micromial compounds that accumulate in plants when under stress such as by infection. It is possible that their detection in Stinking Chamomile is as a result of such an infection, and that they are not normally present (but when are plants under no threat from infection?).