Biologically active compounds can fail to make it as drugs for a variety of reasons—sometimes because they are unstable. Marinomycins, for example, have promising antibiotic and antitumor properties, but the compounds rapidly decompose under ultraviolet light. A team led by Rebecca Goss at the University of St. Andrews in the UK has found a way to protect these sensitive polyenes, by extracting and protecting the antibiotic compound marinomycin A with an unusual casing: grains of pollen (Chem. Sci. 2019, DOI: 10.1039/c9sc01375j).
Pollen is able todeliver drugs and vaccines. The researchers wondered whether it could also protect unstable drug candidates from the harmful effects of UV rays. They treated pollen from the moss Lycopodium clavatumto remove the insides, leaving behind empty shells made of cross-linked polymer sporopollenin. These shells can take up liquids and drugs and also block about 80% of UV light. When the Goss team encapsulated marinomycin A and then dried the shells, they found that the compound is much stabler—enduring for hours, compared with a few seconds for free marinomycin A in solution.