Cactus & Succulent Society
of New Zealand (CSSNZ)

Chemicals in Cacti

Introduction

Like most plants, Cacti contain chemicals - some also found in other plants, some present in just a few (related) plant families and even some exclusive just to cacti.

Mescalin and other Alkaloids

Mescalin is perhaps the most famous (or infamous) hallucinogenic alkaloid or psychoactive drug found in cacti, especially Lophophora williamsii (peyote), but also Trichocereus pachanoi (San Pedro) and ariocarpus species. Also Opuntia, Stenocereus, Cereus and Pereskia contain mescalin, but only in trace amounts.

56 alkaloids have been found in Lophophora, mostly unique to that genus. Alkaloids have been found in many of the Mexican columnar cacti like the Pachycereinae subtribe e.g. Lophocereus and Pachycereus genera.

Alkaloids are synthesised from tyrosine, a common amino acid, via L-Dopa through a series of chemical reactions to an alkaloid.

Many alkaloids are drugs that act on animals, especially the nervous system including altering brain chemicals and leading to hallucinary effects.

Peyote was known to the Chichimeca and Toltec Indian Tribes at least 1890 years before the arrival of the Europeans, still other studies (from cave drawings and remains) show the use of Peyote may actually be 3000 years old.

Betalains

Many angiosperms (flowering plants) contain water soluble coloured pigments like anthocyanins (reds, blues and purples) and betalains (reds and yellows) but not both - they are mutually exclusive.
Anthocyanins are present in carnations, delphiniums and african violets.
Betalains are present in the Beta genus (after which they are named) like beetroot, the portulacas, Bouganvilleas and cacti families - all of which are closely related to each other.

Other less important coloured pigments, for cacti anyway, are the carotenoids - found in carrots, pumpkin and squashes - giving the characteristic yellow/orange colour to these plants.

Betalains are synthesised by a long chemical process from a common amino acid called tyrosine, the first step being the manufacture of L-Dopa (found in the animal brain - responsible for movement and mood) as above in alkaloids.

Crystals

The range and diversity of crystals found in Cacti is nearly equal to that found in all the remaining dicotyledon families combined.

Why?

The plant goes to a lot of trouble, using energy that could be used for growth or reproduction, to produce chemicals that in some cases have no ascertainable beneficial use.

One reason to produce chemicals would be as a defence mechanism, alkaloids themselves are usually sour or unpleasant tasting and certainly put an animal off chewing on that particular plant (plus the hallucinary effects may discourage the animal, or at least make it forget where it is so it can't find the plant again!!!!).
Colours in flowers are very important in terms of attracting pollinators to the pollen receptors, insects see the colours differently to us humans and the colours in the flowers form a pattern to direct the insect.

Nutrients

There are two types of Nutrients: Macro (present in large quantities) and Micro (present in smaller quantities).

Macro nutrients include Nitrogen, Phosphorous, Potassium, Calcium, Magnesium and Sulphur and they are usually important building blocks e.g. DNA is made up of Nitrogen and Phosphorous; Potassium is important for ionic exchange and controlling opening and closing of stomata; Proteins are made up of Nitrogen and Sulphur; Calcium is like the cement that holds the whole plant together; and Magnesium makes up Chlorophyll and involved in enzymes in photosynthesis.

Micro nutrients, although in less quantities, are still very important as they are involved in enzymes and the chemical reactions they initiate, without which the plant couldn't keep on growing and surviving.

Most good fertilisers contain the macro and micro chemicals needed for the plant to grow, for cacti the fertiliser should be low in Nitrogen so as to not force the plant and make it prone to disease or rot, and to grow naturally.
The pH (acid/alkaline balance, pH7 is neutral) also plays a big part in the availability of nutrients to the plant determining what are soluble and therefore absorbable to the plant in it's water uptake. Not many plants can grow in High Alkalinity or Acidity, and those than do are specially adapted to do so. Some cacti (e.g. Ariocarpus) grow better in alkaline conditions (pH8) while others (e.g. Gymnocalycium??) prefer acid (pH6).