Affiliation:
1. Department of Medicinal Chemistry, Ernest Mario School of Pharmacy Rutgers University Piscataway New Jersey USA
2. Rutgers Core Facility for Natural Products and Bioanalysis Rutgers University New Brunswick New Jersey USA
3. New Use Agriculture and Natural Plant Products Program (NUANP), Department of Plant Biology, Center for Agricultural Food Ecosystems, Institute of Food, Nutrition & Health and Natural Products Rutgers University New Brunswick New Jersey USA
Abstract
AbstractIntroductionCatnip (Nepeta cataria, L.) has well‐documented applications in arthropod repellency because of its bioactive iridoids. Long‐term stability of nepetalactones and other iridoids in N. cataria are needed to develop as effective pest repellents.ObjectivesThe present work intends to measure iridoid concentration over time in biomass, plant extracts, and extract solution while identifying degradative byproducts under different storage conditions.MethodologySamples of desiccated biomass, ethanol extract, and extract in ethanol solution were stored in ambient light or darkness. Through UHPLC‐QTOF/MS or UHPLC‐QQQ/MS, the concentration of Z,E‐nepetalactone, E,Z‐nepetalactone, nepetalic acid, and dihydronepetalactone were examined over 2 years and statistically analyzed for determination of best storage practices. Degradation kinetics were applied to each analyte using graphical estimation. With targeted formula searching, degradative byproducts were identified and quantified.ResultsLight exposure caused significant decreases in E,Z‐nepetalactone concentration in all sample types, while having no effect on Z,E‐nepetalactone as it decayed more rapidly. Extract samples lost nepetalactone content faster than biomass or extract solution. Dihydronepetalactone levels were low, but never declined over 2 years. Nepetalic acid increased over some periods, depending on sample type, indicating a relationship between the acid and nepetalactone. Four degradative byproducts—nepetonic acid, dehydronepetalactone, an anhydride, and an ethanolic ester—were identified, with variable responses to light exposure.ConclusionsProtecting catnip products from light is necessary to preserve nepetalactones, and a discernable difference in nepetalactone isomer stability was discovered. Identifying Nepeta chemotypes rich in dihydronepetalactone may provide more resilient botanicals as starting materials for processing.