Araceae

One of the most recognisable plant families in the world, defined by its inflorescence: a fleshy spike of tiny flowers, the spadix, wrapped in a modified leaf, the spathe. Several genera are thermogenic — they heat the spadix above ambient temperature to volatilise scent, which is how skunk cabbage melts its way up through late-winter snow.

The family’s defining pharmacological feature is a mechanical one, and understanding it explains almost everything about how aroids are used.

Aroid tissue is packed with calcium oxalate raphides — bundles of needle-sharp crystals held in specialised cells that discharge under pressure, driving the needles into the mucosa of anything that chews the plant. The result is immediate burning, swelling of lips, tongue and throat, and in severe cases airway compromise. It is not an absorbed toxin; it is a puncture injury delivered at microscopic scale, and it is why raw aroid is essentially unswallowable while thoroughly cooked or long-dried aroid is a staple food for hundreds of millions of people (taro).

That same processing requirement runs through the family’s medicinal members. Pinellia (Ban Xia) is one of the most-used herbs in Chinese medicine, for phlegm and for nausea — and it is never used raw; the classical processing methods with ginger and alum exist specifically to destroy the raphides. The same is true of Arisaema (Tian Nan Xing).

In North America two unrelated plants share the name “skunk cabbage” and both are aroids, but they are different genera with different histories. Eastern skunk cabbage (Symplocarpus foetidus) has a real Eclectic materia medica reputation as a respiratory antispasmodic. Western skunk cabbage — Lysichiton americanus — does not, and its evidence should never be merged with the eastern plant’s.

Sweet flag (Acorus calamus) sits outside the pattern entirely: it has no significant raphides, and its safety question is β-asarone, a genotoxic and hepatocarcinogenic phenylpropene restricted in food use. Modern classifications place Acorus in its own family, Acoraceae, as the earliest-diverging branch of the monocots.

• Calcium oxalate raphides — the family signature, and the reason “chemistry” is only half the story. Raphide injury is now understood to be pro-inflammatory in its own right, triggering local cytokine release rather than merely abrading tissue.
• Lectins — mannose-binding lectins accompany the raphides in several genera and are thought to amplify the inflammatory response.
• Alkaloids and amines — coniine has been reported from Arum, and various simple amines occur through the family, but no aroid is defined by its alkaloids.
• Phenylpropenes — β-asarone and α-asarone, concentrated in Acorus.
• Starch — the reason taro, konjac and elephant-foot yam are crops at all.