Screening the PRISM Library against Staphylococcus aureus Reveals a Sesquiterpene Lactone from Liriodendron tulipifera with Inhibitory Activity.

Infections caused by the bacterium Staphylococcus aureus continue to pose threats to human health and put a financial burden on the healthcare system. The overuse of antibiotics has contributed to mutations leading to the emergence of methicillin-resistant S. aureus, and there is a critical need for the discovery and development of new antibiotics to evade drug-resistant bacteria. Medicinal plants have shown promise as sources of new small-molecule therapeutics with potential uses against pathogenic infections. The principal Rhode Island secondary metabolite (PRISM) library is a botanical extract library generated from specimens in the URI Youngken Medicinal Garden by upper-division undergraduate students. PRISM extracts were screened for activity against strains of methicillin-susceptible S. aureus (MSSA). An extract generated from the tulip tree (Liriodendron tulipifera) demonstrated growth inhibition against MSSA, and a bioassay-guided approach identified a sesquiterpene lactone, laurenobiolide, as the active constituent. Intriguingly, its isomers, tulipinolide and epi-tulipinolide, lacked potent activity against MSSA. Laurenobiolide also proved to be more potent against MSSA than the structurally similar sesquiterpene lactones, costunolide and dehydrocostus lactone. Laurenobiolide was the most abundant in the twig bark of the tulip tree, supporting the twig bark's historical and cultural usage in poultices and teas.

Analysis of botanicals and botanical supplements by LC-MS/MS-based molecular networking: Approaches for annotating plant metabolites and authentication.

Prior to the advent of modern medicine, humans have used botanicals extensively for their therapeutic potential. With the majority of newly approved drugs having their origins in natural products, plants remain at the forefront of drug discovery. Continued research and discovery necessitate the use of high-throughput analytical methods to screen and identify bioactive components and potential therapeutic molecules from plants. Utilizing a pre-generated plant extract library, we subjected botanicals to LC-MS/MS-based molecular networking to determine their chemical composition and relatively quantify already known metabolites. The LC-MS/MS-based molecular networking approach was also used to authenticate the composition of dietary supplements against their corresponding plant specimens. The networking procedures provided concise visual representations of the chemical space and highly informative assessments of the botanicals. The procedures also proved to define the composition of the botanical supplements quickly and efficiently. This offered an innovative approach to metabolite profiling and authentication practices and additionally allowed for the identification of new, putatively unknown metabolites for future isolation and biological evaluation.

Incorporating LC-MS/MS Analysis and the Dereplication of Natural Product Samples into an Upper-Division Undergraduate Laboratory Course.

Growth in the biomedical and biotechnology sectors requires a highly trained and highly skilled workforce to answer the next great scientific questions. Undergraduate laboratory courses incorporating hands-on training based in authentic research position soon-to-be graduates to learn in environments that mirror that of academic, industrial, and government laboratories. Mass spectrometry is one of the most broadly applied analyses carried out in the biomedical and pharmaceutical sciences and thus it is essential that upper-division students gain hands-on experience in techniques and analytical workflows in mass spectrometry. Our pre-course assessments identified weaknesses in student experience and knowledge in the fundamentals of mass spectrometry, supporting that it was a necessary area for improvement. We incorporated a laboratory experiment focused on tandem mass spectrometry and database searching into a preexisting mini-semester project devoted to identifying metabolites from medicinal plants. Implementation of the experiment allowed students to make more confident metabolite identifications, introduced them to a cutting-edge database analysis platform (GNPS: Global Natural Products Social Molecular Networking), and increased student experience and knowledge of mass spectrometry in addition to the principle of dereplication of samples derived from nature.