Abstract
Natural products from medicinal plants serve as an invaluable resource for drug discovery and development. However, low-abundance natural products are often understudied due to the challenges of obtaining sufficient quantities for pharmacological testing in cells or animals. Additionally, their complex stereochemistry and functional groups make chemical synthesis and purification difficult. In this study, we showcased the power of biosynthetic approaches to explore these underexplored compounds, using the low-abundance polyphyllin trillin 6'-O-glucoside from Paris polyphylla as an example. We identified two trillin 6'-O-glucosyltransferases required for its biosynthesis and successfully reconstructed the entire pathway in Nicotiana benthamiana. We demonstrated that trillin 6'-O-glucoside exhibits anti-bacterial activity comparable to major polyphyllins like polyphyllins I, II, and VII. Notably, it also showed much lower hemolytic activity, a common side effect of those major polyphyllins. Together, our study underscores the advantages of employing biosynthetic approaches to explore natural products that exist in low or trace abundances yet possess equally important pharmacological activities.