Progress on biosynthesis and function of the natural products of Zi Cao as a traditional Chinese medicinal herb.

Zi Cao is an important traditional medicinal plant resource in China. Shikonin and its derivatives, as the purple-red naphthoquinones among natural products of its roots, are commonly used clinically in the treatment of sores and skin inflammations. Over the past few decades, due to their highly effective multiple biological activities, pharmacological effects, good clinical efficacy and high utilization value, shikonin and its derivatives have attracted increasing attention of domestic and foreign researchers. For this reason, the wild plant germplasm resources have been suffering a grievous exploitation, leading to a serious threat to the habitat. With the development of the biosynthesis, molecular metabolism and biotechnology, as well as the continuous innovation of research methods on the biological activities and pharmacological effects of plant natural products, significant progress has been made in the research on the biosynthetic pathways and related regulatory genes of shikonin. The pharmacological action and its mechanism of shikonin have also been deeply elucidated, which greatly promoted the basic research and clinical application development of shikonin. In this review, we briefly introduce and analyze the classification of Zi Cao, structure and composition of natural shikonin and its biosynthesis pathway, functional genes related to the regulation of shikonin biosynthesis, and biological activities and pharmacological functions of shikonin. Finally, we address possible prospective for the trend on the future research and development of natural shikonin and its derivatives, hoping to provide a useful reference for the deep mining and development of medicinal natural products from important Chinese medicinal materials, and to promote the modern development of traditional Chinese medicine.