Extract from the Lepidium meyenii plant, commonly known as the maca plant, can protect the skin of rats against UV radiation, according to research performed by Cynthia Gonzales-Castaneda and Gustavo F. Gonzales at the University of Peru. The team applied the maca extracts to the dorsal skin of rats and found that the aqueous extract that was obtained after boiling the plant gave better protection than the conventional sunscreen used as a control. UV protection across the spectrum The maca plant grows exclusively in the Peruvian Central Andes 4000-4500 m above sea level. The plant has been traditionally used for its nutritional and fertility enhancing properties, however there has never been any investigation of its UV protective qualities, according to the authors. Two extracts were prepared from the plant - one boiled with water and the other mixed with water. Boiled and non-boiled maca extracts were applied to the shaved dorsal skin of rats, along with a commercial SPF 30 sunscreen, and distilled water to represent the vehicle. An area of the dorsal skin was left clear of preparations to provide an irradiated control. UV radiation was carried out once a week for three consecutive weeks and UV damage to the skin was measured by the epidermal epithelia height. Both maca extracts had a protective effect against UV irradiation, however the boiled extract provided better protection than the non boiled, according to the study. Furthermore, the boiled extract provided better protection against the radiation than the commercial sunscreen used as a control. Similar experiments were performed that illustrated the dose dependent effects of the maca extracts against UVA and UVB radiation, according to the researchers. Polyphenols may provide the protection Although the active compounds responsible for the protective effect of the maca plant are unknown, the scientists hypothesize that polyphenols and glucosinolates may play a role. The increased efficacy of the boiled extract compared to the non-boiled may be explained by structural changes to the compounds caused by boiling, say the researchers. It is thought that the compounds may make up part of the plant's own protective mechanism against UV and concentrations tend to increase in plants grown at higher altitudes. Polyphenols from tea have also been reported to protect the skin against UV radiation and CosmeticsDesign has recently reported on a black tea extract shown to have protective qualities.