The Chemistry of Wild Garlic

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Spring is in the air, and it’s likely that, in your local forest, so too is the distinctive scent of wild garlic. Also known as ‘ramsons’ or ‘bear’s garlic’, green carpets of wild garlic swell in the forest’s undergrowth at this time of year. Here we take a look at their chemistry, and why, if you’re out foraging for it, you want to be sure you know how to identify it!

Wild garlic, as the name suggests, is also a member of the Allium family that includes common garlic, onions, and chives. Unlike the garlic more commonly used in the kitchen, wild garlic’s leaves are more commonly eaten than the much smaller bulbs. It’s hard to fail to notice the areas in which it grows, due to the strong smell of garlic they send wafting on the air – a smell that, unsurprisingly, has a lot in common with ordinary garlic on a chemical level.

The chemical precursors to this smell are a group of sulfur-containing carbon-based compounds known as sulfoxides. A number of these are found in wild garlic leaves, with the most common being methiin, alliin, and isoalliin. Though these compounds do not directly cause the smell of garlic, they are responsible for generating the compounds that do.

Much like in the case of garlic, the chemistry of which we’ve examined previously, the compounds producing the characteristic garlic smell are only produced when the plants are mechanically damaged. This can be in a number of ways, from being trampled underfoot, to being munched on by bugs or insects. When this happens, enzymes are released which convert the sulfoxides in the leaves into a range of different chemical compounds.

Some of the compounds produced are thiosulfinates. These compounds are very volatile – they evaporate easily and waft through the air towards your nose. One of these compounds, allicin, is one of the main chemical entities responsible for the garlic aroma that permeates the woods in which wild garlic grows. It’s actually a somewhat unstable compound, and relatively quickly breaks down further into a range of other sulfur-containing compounds, which can also contribute to the aroma.

This cascade of chemical reactions that occur when the plant is damaged aren’t designed for olfactory appeal – allicin is actually a molecule which has both antibacterial and antifungal properties. Essentially, it’s the plant’s defence mechanism, triggered by any damage, which is intended to ward off pests. Allicin’s effects are thought to be due to its ability bind to sulfur-containing groups in proteins within cells and interfere with cell processes.

Luckily, human cells are unaffected by allicin, so we have no problems eating either common or wild garlic. However, the breakdown products of allicin in the body are what lead to “garlic breath”, a phenomenon that isn’t avoided with wild garlic either! Interestingly, cows fed wild garlic produce milk flavoured by some of these molecules, and apparently in Switzerland some farmers used to make butter from this milk – which sounds like a really long-winded way of making garlic butter!

Though wild garlic is both a free and tasty addition to culinary dishes (it can be used to make a mean pesto with a garlicky punch), care does have to be taken when collecting it. The leaves have a passing similarity to several other plants which you really don’t want to be adding to a soup. Lily of the valley is one such plant, the leaves of which can be mistaken for wild garlic, but which also contain cardiac glycosides. These compounds, as the name suggests, can have serious effects on the heart, and eating even a small quantity can lead to death.

Another plant whose leaves can be confused with those of wild garlic is the autumn crocus, or meadow saffron. This plant contains the alkaloid colchicine, which in small amounts is actually a medicine used to treat gout. However, in another classic example of the dose making the poison, ingesting larger amounts can cause multiple organ failure.

As a result of these risks, caution is advised if you are tempted to go on a wild garlic hunt. One of the easiest ways to distinguish between wild garlic and the plants it can be confused with is simply by smell. The leaves of lily of the valley and the autumn crocus do not emit the characteristic garlic smell, which can be checked for simply by rubbing the leaves. As always, the best advice is, if you’re not sure, don’t eat it!

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