The cleaner synthesis was used to control fall armyworms, one of the main threats to corn crops in many parts of the world. The new method avoids toxic solvents and strong mineral acids that were needed in earlier processes.

Instead, it relies on a metal catalyst that works at low levels: one catalyst molecule per 200 molecules of starting material. The catalyst could be easily recovered at the end of the chemical reaction and recycled several times, reducing waste.

Flavones protect plants against a variety of bacteria and insects. Some flavones also show beneficial effects in humans as antioxidants, anti-inflammatory agents, antimicrobials and anticancer agents.

The researchers made synthetic flavones using the greener technique and found that the chemicals were effective against the armyworm larvae. Based on these results, the researchers then created a computer model to predict which natural flavones might be worth testing as pesticides. They analyzed the structures of more than a dozen plant flavones and found two with characteristics in common with the chemicals that worked against armyworms.

One of the natural flavones, luteolin, occurs naturally in the human diet, in carrots, peppers, celery, and some spices. The other, apigenin, is common in citrus fruit, tea, and a variety of vegetables. Both chemicals are often cited for their therapeutic effects in humans.

The next step is for scientists to test whether these two natural flavones do indeed kill insects, as predicted by the model. While the natural flavones would probably have minimal environmental impacts if applied as pesticides, the synthetic flavones reported in the study were not tested for environmental persistence or toxicity to organisms besides armyworms. Those experiments would confirm whether the greener preparation leads to greener pesticides.