Pharmacodynamics of frigid zone plant Taxus cuspidata S. et Z. against skin melanin deposition, oxidation, inflammation and allergy

Abstract Background Taxus cuspidata S. et Z. is a precious species of frigid zone plant belonging to the Taxaceae family, which possesses anticancer, anti-inflammatory, hypoglycemic, and antibacterial pharmacological properties. While taxane extracted from Taxus chinensis has been reported to elicit antioxidant activities, whether Taxus cuspidata S. et Z. has skin-protective actions against injuries remained unknown. This study aims to explore the pharmacological effects of three Taxus extracts on skin melanin deposition, oxidation, inflammation, and allergy so as to provide new ideas for the prevention and treatment of various diseases related to skin damage. Methods Skin melanin deposition was evaluated by measuring melanin content in the skin of guinea pigs by alkali lysis method. Antioxidant capacity was evaluated by measuring superoxide dismutase (SOD) concentration and glutathione (GSH) content in skin tissue homogenates of Kunming mice by SOD assay kit and micro reduced GSH assay kit. The quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to examine the levels of both SOD and recombinant glutathione peroxidase 4 (GPX4). Skin inflammation was evaluated by xylene-induced ear swelling test and egg-white-induced paw swelling test in mice. In a mouse model of skin allergy induced by 4-aminopyridine (4-AP), allergy was determined by licking body counts and histamine concentrations in tissue homogenates using enzyme-linked immunosorbent assay (ELISA) kits. Two proinflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-1β were measured by qRT-PCR. Hematoxylin and eosin (HE) staining was conducted to assess the degree of skin lesion. Results All three Taxus extracts including Taxus chinensis essential oil, Taxus chinensis extract and Taxus chinensis extract compound reduced the melanin deposits in the back skin relative to the non-treated control animals, of which Taxus chinensis essential oil produced the greatest effect. In contrast, the three Taxus extracts elevated SOD and GSH levels in the skin tissues, and the highest increase was seen with Taxus chinensis essential oil. Three Taxus extracts, especially Taxus chinensis essential oil, effectively reduce the rate of ear and paw swelling. All three Taxus extracts reduced the number of body licks, the levels of TNF-α and IL-1β, and the histamine content in tissue homogenates of mice and alleviated skin damage. Consistently, Taxus chinensis essential oil yielded the greatest magnitude of decreases. Conclusion While all three Taxus extracts possessed the anti-skin melanin deposition, oxidation, and allergy properties, Taxus chinensis essential oil produced the superior effects.