Making light of molecule manufacture

You may not have heard of cyclodextrins, but chances are you’ve used or ingested things made with them. The doughnut-shaped, biodegradable sugar molecules are useful for making a range of food, pharmaceutical and household products.

Gamma-cyclodextrin, the largest and most water-soluble cyclodextrin, is currently produced with an expensive and energy-intensive distillation. But research published in Chem has described an easier way of making the molecule using light.

“These compounds are biodegradable, biocompatible, benign and commonly used,” says Ivan Aprahamian, a professor of chemistry at Dartmouth College, US, and co-author on the paper. “We are making production much more efficient so that they can be even more available to industry.”

Gamma-cyclodextrin is made from reacting enzymes with starch, but it’s hard to isolate from the molecules used to form it. This is why steam distillation is used to purify it industrially.

The new method uses a type of compound known as a hydrazone, which is sensitive to different wavelengths of light. The hydrazone sits inside the “hole” of the gamma-cyclodextrin doughnut (or, more scientifically, the cavity).

“Once you introduce light, it changes shape and leaves the cavity, facilitating the isolation of the compound. There is no more need for steam distillation,” says Aprahamian.

The molecule is currently used to increase the shelf life of medications, as well as making them easier to digest. Its doughnut shape makes it good at both capturing and slowly releasing molecules in the air – making it helpful in air fresheners and fragrances.

The researchers say that they hope cyclodextrins can now be used more widely with this more effective process.

”The unique structure of this molecule helps it hold bulky molecules like vitamins and sensitive dyes,” says Sirun Yang, first author on the paper and a graduate student at Dartmouth. “Gamma-cyclodextrin was already useful to industry, now we’re making it more accessible for producers of pharmaceuticals, food and household products.”

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