Angela Calderón Discusses Importance of Sustainable Analysis Techniques

When conducting analytical chemistry and developing routine analysis methods, it is important to consider how environmentally friendly different techniques and substances are. Within recent years, scientists have begun to consider how potentially problematic substances can be replaced with sustainable substitutes. One such example can be found in the study, “Application of eco-friendly natural deep eutectic solvents (NADES) in HPLC for separation of complex natural products: Current limitations and future directions”. In this study, scientists investigated how volatile organic solvents (VOSs) can be replaced using natural product (NP) mixtures. Natural deep eutectic solvents (NADES), the substances that are being pitched as replacements for VOSs, are more cost-efficient and easily produced, while also having low lethality and high ecological compatibility, which are derived from components that are biosynthesized and metabolized by most living organisms.

Angela Calderón of Auburn University is one of the scientists behind this study, and recently, LCGC International secured an interview with her. In this, she discusses her sentiments behind the original study, while also discussing a potential future where scientists can use more sustainable analytical techniques.

Q) What are the usual procedures done for separating natural products (NPs)? How are they different than the proposed natural deep eutectic solvents (NADES) approach?

The most common extraction method for natural products is typically solid-liquid extraction. Current separation techniques for NP mixtures relied heavily on usage of volatile organic solvents (VOSs). NADES are mixtures of naturally occurring eutectic substances (such as sugars, amino acids, organic acids, and other primary and secondary metabolites) combined at specific molar ratios to yield the lowest melting point or eutectic point. NADES have been described as cost-efficient and easily produced, as well as having low lethality and high ecological compatibility due to components that are biosynthesized and metabolized by most living organisms.

Q) What makes separating NPs important?

Separating natural products (NPs) is a very challenging yet crucial process to increase knowledge about the complexity and diversity of the metabolic processes of plants, animals, and microorganisms and the identification and isolation of bioactive natural compounds. Natural products (NPs) offer a nearly endless source of potential new drug molecules and are often the framework of analogs created for more specific target binding and increased efficacy, safety, and delivery.

Q) Are there other applications that NADES are currently used for?

Natural deep eutectic solvents (NADES) have been used in chromatography as extraction media, HPLC mobile phase additives, and as an HPLC major mobile phase component.

Q) What efforts are being made to further this research/these findings?

Our review paper identified articles that focused on using NADES as extraction solvents for natural products, particularly polyphenols or reported NADES viscosities to establish a database of NADES which could be used as HPLC mobile phases under various conditions.We also summarized other challenges that limit NADES application in HPLC mobile phase include low volatility; NADES wavelength cutoffs, pertinent for ultraviolet (UV) and Fluorescent (FL) detectors and impurities as well as provided suggestions for overcoming these limitations. This paper provided scientific information to help widen the applications of NADES into HPLC systems in the future.

Q) What makes it so important to focus on the environmental impacts of chromatographic techniques?

The usage of volatile organic solvents (VOSs), which have acute oral, dermal, and inhalation toxicities, are also ecotoxic, which can prove dangerous. The estimated annual amount of organic chemical waste produced globally by high performance liquid chromatography (HPLC) users alone is up to 52 million liters, and as a result, approximately 9.8 million people are occupationally exposed to VOSs.

This interview has been lightly edited for clarity.

Reference

(1) Heck, K. L.; Si, L.; Jung, D. J.; Calderón, A. I. Application of Eco-Friendly Natural Deep Eutectic Solvents (NADES) in HPLC for Separation of Complex Natural Products: Current Limitations and Future Directions. J. Pharm. Biomed. Anal. 2024, 244, 116102. DOI: 10.1016/j.jpba.2024.116102

About the Interviewee

Angela I. Calderón is a Gilliland Endowed Professor in the Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University. She received her B.S. in Pharmacy from the University of Panama, Panama City, Republic of Panama (1990), MSc. in Pharmacognosy from the University of Illinois at Chicago, Chicago, Illinois under the supervision of Dr. Djaja Djendoel Soejarto and Dr. Cindy K. Angerhofer (1997), and Ph.D. in Pharmacognosy from the University of Lausanne, Lausanne, Switzerland under the guidance of Prof. Kurt Hostettmann (2002). Then, she conducted her postdoctorate on biomedical applications of mass spectrometry at Prof. Richard B. van Breemen’s laboratory at the University of Illinois at Chicago (2006-2008). She joined the faculty at Auburn University College of Pharmacy as an Assistant Professor in August 2008.

Dr. Calderón specializes in natural drug products research, specifically applications of mass spectrometry to natural products drug discovery, and quality and safety assessment of botanical dietary supplements. Over the last sixteen years, she has authored 52 publications, 1 US patent, and 5 book chapters. She also has received research funding from agencies that include National Center for Complementary and Integrative Health (NCCIH) and the Office of Dietary Supplements (ODS) of the National Institutes of Health (NIH), American Society of Pharmacognosy, United States Pharmacopeia, Auburn University Research Initiative in Cancer (AURIC), and botanical dietary supplements industry.

Dr. Calderón is currently an expert member of the United States Pharmacopeia Botanical Pan-American Expert Panel. She also was a member of the United States Pharmacopeia Botanical Dietary Supplements and Herbal Medicines Expert Committee. Additionally, she was the Section Editor of Pharmacognosy of Combinatorial Chemistry & High Throughput Screening and Pharmaceutical Biology and is a current member of the Advisory Board of Planta Medica She has been grant proposal reviewer for National Institutes of Health (NIH), National Science Foundation (NSF), USA and German Federal Ministry of Education and Research (BMBF) and Project Management Jülich (PtJ) and Deutsche Forschungsgemeinschaft (German Research Foundation), Germany, and International Foundation for Science (IFS), Sweeden.